University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Urine

Classification: Biological fluid -> urine -> human

Citations 76

"Determination Of Selenium Balance In Healthy Children By AAS-hydride Generation And By INAA Technique"
Acta Aliment. 2002 Volume 31, Issue 3 Pages 227-234
Adányi, N., Váradi, M., Sziklai-László, I., Snyder, P., Snyder, R. D., Cser, M. Á.

Abstract: Total daily Se intake was determined by duplicate diet collection, venous blood samples were taken and urine was collected over 24 h in order to measure selenium input and output in healthy, American and Hungarian children aged 8 to 17 living in Budapest. The American children consumed not only locally processed food. Food samples were weighed, mixed, homogenised and the Se content was determined by Instrumental neutron activation analysis (INAA). The Se concentration of blood, plasma and urine samples was determined by atomic absorption spectrometry-hydride generation (AAS-HG) after wet digestion. Se intake calculated for wet weight was 62±18.5 µg/day in American children. In the Hungarian children the mean Se intake was about 35% less than in the Americans. Se concentrations in plasma were 0.84±0.16, in whole blood 1.13±0.17 µmol L-1 in the Americans, higher than those in healthy Hungarian children (0.64±0.10 and 0.83±0.12 µmol L-1, respectively) of similar age and gender. Urinary Se output calculated for creatinin was higher in the children from abroad (27.0±9.5 µg Se/day/g creatinin) compared to Hungarians (11.0±5.0 µg Se/day/g creatinin).
Selenium Spectrophotometry Volatile generation

"Determination Of Flufenamic Acid And Mefenamic Acid In Pharmaceutical Preparations And Biological Fluids Using Flow Injection Analysis With Tris(2,2 -bipyridyl)ruthenium(II) Chemiluminescence Detection"
Anal. Chim. Acta 2000 Volume 416, Issue 1 Pages 87-96
Fatma A. Aly, Salma A. Al-Tamimi and Abdulrahman A. Alwarthan

Abstract: A novel chemiluminescent method using flow injection has been investigated for the rapid and sensitive determination of flufenamic and mefenamic acids. The method is based on a tris(2,2-bipyridyl)ruthenium(III) chemiluminescence reaction. Ru(bipy)(3)(3+) is chemically generated by mixing two streams containing solutions of tris(2,2-bipyridyl)ruthenium(II) and acidic cerium(IV) sulfate. After selecting the best operating parameters calibration graphs were obtained over the concentration ranges 0.07-6.0 and 0.05-6.0 µg mL-1 for flufenamic acid and mefenamic acid, respectively. The Limits of detection (s/n = 3) were 3.6 x 10^-9 M flufenamic acid and 2.1 x 10^-7 M mefenamic acid. The method was successfully applied to the determination of these compounds in pharmaceutical formulations and biological fluids. A proposal for the reaction pathway was given.
Flufenamic acid Mefenamic acid Chemiluminescence Method comparison Optimization

"Flow Injection Biamperometric Determination Of Chloramphenicol And Related Nitro Compounds By On-line Chemical Photodegradation"
Anal. Chim. Acta 2000 Volume 404, Issue 1 Pages 141-150
J. A. García Bautista, J. V. García Mateo and J. Martínez Calatayud

Abstract: An unsegmented continuous-flow assembly for the determination of chloramphenicol is proposed. The determination is based on the on-line photodegradation of the drug in an NH4+/NH3 buffer at pH 10.4 by using a photoreactor consisting of a 697 cm long x 0.8 mm ID piece of PTFE tubing coiled around an 8 W low-pressure mercury lamp. Photodegraded chloramphenicol is detected by photolytic cleavage of nitrite from the:parent compound as well as by organic oxidizing photofragments, and their subsequent reaction with iodide ion, which is monitored biamperometrically. Triiodide thus formed is detected in excess iodide solution by polarizing two platinum electrodes at 100 mV. The calibration graph is linear up to 8 mg L-1 chloramphenicol; the Limit of detection is 0.05 mg L-1, the relative standard deviation is 0.4% (for 25 replicates of 10 mg L-1 drug) and the throughput 68 samples h-1. The proposed method was used to determine chloramphenicol in commercially available pharmaceutical formulations and human urine.
Chloramphenicol Biamperometry Electrode Clinical analysis UV reactor Optimization

"Coupling On-line Preconcentration By Ion-exchange With ETAAS. A Novel Flow Injection Approach Based On The Use Of A Renewable Microcolumn As Demonstrated For The Determination Of Nickel In Environmental And Biological Samples"
Anal. Chim. Acta 2000 Volume 424, Issue 2 Pages 223-232
Jianhua Wang and Elo Harald Hansen

Abstract: A novel way of exploiting flow injection/sequential injection (FIA/SIA) on-line ion-exchange pre-concentration with detection by electrothermal atomic absorption spectrometry (ETAAS) is described and demonstrated for the determination of trace-levels of nickel. Based on the use of a renewable microcolumn incorporated within an integrated µFI-system, the column is loaded with a defined volume of small beads of an SP Sephadex C-25 cation-exchange resin and subsequently exposed to a metered amount of sample solution. However, instead of eluting the retained analyte from the organic ion-exchange resin, the beads are along with 30 µL of carrier (buffer) solution transported via air segmentation directly into the graphite tube, where they are ashed during the pyrolysis and atomization process. The ETAAS determination is performed in parallel with the pre-concentration process of the ensuing sample. An enrichment factor of 72.1, a detection limit of 9 ng L-1, along with a sampling frequency of 12 h-1 were obtained with 150 s of sample loading time at a sample flow rate of 12 µL s-1 (corresponding to 0.72 mL min-1). The relative standard deviations were 3.4%. The procedure was validated by determination of the nickel contents in two certified reference materials and in a human urine sample.
Nickel Spectrophotometry Reference material Solvent extraction Preconcentration Column Sephadex Sequential injection Interferences Optimization

"Preconcentration And Determination Of Trace Chromium(III) By Flow Injection Inductively-coupled Plasma Atomic Emission Spectrometry"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 487-490
Alan G. Cox and Cameron W. McLeod

Abstract: The method previously described [Analyst (London), 1985, 110, 331] is modified by use of the alumina column in basic instead of acidic form and is applied to human urine. The Cr is adsorbed from the sample in 0.02 M NH3 as carrier and is eluted with 2 M HNO3. The response is rectilinear from 10 to 1000 µg L-1 with a limit of detection of 0.92 µg L-1 and a coefficient of variation for 10 µg L-1 of 12% (n = 10). For a standard urine reference sample of certified value of 0.085 ± 0.006 µg mL-1, a result of 0.079 ± 0.004 µg mL-1 has been obtained (n = 10).
Chromium(III) Clinical analysis Spectrophotometry Alumina Column Reference material Preconcentration

"Flow Injection Methods For The Determination Of Uracil Derivatives With Voltammetric Detection"
Anal. Chim. Acta 1988 Volume 211, Issue 1-2 Pages 175-193
B. Bouzid and A. M. G. Macdonald

Abstract: Flow injection methods are described for the determination of 18 uracil derivatives by differential pulse amperometry (d.p.a.) and differential pulse cathodic-stripping voltammetry (d.p.c.s.v.). The carrier stream was 0.05 M Na2B4O7 - 0.01 M KNO3 - 0.1 M HNO3 (or NaOH) at pH 7.6 containing 0.001% of Triton X-100 (to avoid the need for deaeration) for the detection of compounds having peak potentials in the range 180 to 70 mV (vs. Ag - AgCl). Calibration graphs were rectilinear for most compounds in the range 1 to 0.1 µM by d.p.a. and about one order of magnitude lower by d.p.c.s.v. The limit of determination for 5-iodouracil was 5 nM (~1.2 ng mL-1). Pre-separation was needed for applications to blood or urine. A deproteinization procedure followed by reversed-phase HPLC is described for the simultaneous determination of 5-fluorouracil, 5'-deoxy-5-fluorouridine and uric acid in human serum, with sequential spectrophotometric (268 nm) and amperometric detection.
Amperometry HPLC Voltammetry Stopped-flow Triton X Surfactant

"Design And Properties Of A Flow Injection Analysis Cell Using Potassium-selective Ion-sensitive Field-effect Transistors As Detection Elements"
Anal. Chim. Acta 1991 Volume 245, Issue 2 Pages 159-166
Peter D. van der Wal, Ernst J. R. Sudhölter and David N. Reinhoudt

Abstract: The combination of flow injection analysis (FIA) and chemically modified ion-sensitive field-effect transistors (CHEMFETs) is described. In a wall-jet cell, two identical potassium-selective CHEMFETs were used for a differential measurement using a platinum (pseudo-)reference electrode. Silicone-rubber membrane materials, chemically bound to the SiO-2 gate oxide, were used with valinomycin as the ionophore. The optimized FIA system showed a linear response of 56 mV per decade for potassium concentrations above 5 times 10^-5 M. Preliminary results of potassium determinations in human serum and urine samples are presented.
Potassium Field effect transistor Silicone membrane Optimization Apparatus

"Spectrofluorimetric Determination Of Emetine By Flow Injection Using Barium Peroxide And UV Derivatization"
Anal. Chim. Acta 1993 Volume 279, Issue 2 Pages 293-298
C. Gómez Benito and T. García Sancho, J. Martínez Calatayud*

Abstract: Emetine, an alkaloid in ipecacuanha, is an amoebicide acting principally in the bowel wall and in the liver. Sample stream (1 ml/min) was merged with a reagent stream (0.55 ml/min) containing 40 mg of barium peroxide in 4.0 M phosphoric acid. A portion of the mixture was injected into a water carrier stream (4.3 ml/min) and transported through a PTFE tube (2.65 m x 0.5 mm) coiled around a Hg lamp before fluorimetric detection at 452 nm (excitation at 350 nm). The calibration graph was linear for 0.05-50 µg/ml of emetine. The RSD (n = 34) for 3.5 µg/ml of emetine was 0.65% and the sample throughput was 67/h. The tolerance limits for foreign compounds found in pharmaceutical materials are listed. Resorcinol produces the most serious interference. The repetitive analysis of human urine and injection solution spiked with 4 µg/ml of emetine resulted in relative errors of 3.4 and 0.3%, respectively.
Emetine Fluorescence Spectrophotometry Photochemistry UV reactor Interferences

"Chemiluminescence Determination Of Catecholamines In Human Blood Plasma And Urine Using Diphenylethylenediamine As Pre-column Derivatization Reagent In Liquid Chromatography"
Anal. Chim. Acta 1994 Volume 298, Issue 3 Pages 431-438
Gamal H. Ragab, Hitoshi Nohta, Masaaki Kai and Yosuke Ohkura

Abstract: A chemiluminescence detection of the fluorescent derivatives of catecholamines (norepinephrine, epinephrine and dopamine) and isoproterenol as an internal standard is described for the highly sensitive liquid Chromatographic determination of these compounds. The amines were converted by reaction with 1,2-diphenylethylenediamine into the corresponding fluorescent derivatives, which were separated on a reversed-phase column (TSK gel ODS-120T) with isocratic elution. The derivatives in the column eluate were detected by the post-column chemiluminescence reaction system using bis[4-nitro-2-(3,6,9-trioxade-cyloxycarbonyl)phenyl] oxalate and hydrogen peroxide. The method allowed the determination of catecholamines in 50 µL of human blood plasma and 10 µL of 20 times diluted urine. The detection limits for the amines were 150-450 amol per 100 µL injection volume at a signal-to-noise ratio of 3.
Catecholamines Chemiluminescence Pre-column derivatization

"Flow Injection Spectrophotometric Determination Of Carbimazole And Methimazole"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 457-461
C. Sánchez-Pedreño*, M. I. Albero, M. S. García and V. Ródenas

Abstract: A flow injection method for the determination of carbimazole (I) and methimazole (II) was based on the formation of yellow complexes between these antithyroid drugs and Pd(II). A 72 µL portion of antithyroid solution was injected into a water carrier stream (1.5 ml/min) which was merged with a reagent stream (1.5 ml/min) containing 0.25 mM PdCl2 in 0.5 M HCl. After passing through the reaction coil (2 m x 0.5 mm i.d.), the absorbance of the flow was measured at 325 nm for both analytes. The calibration graphs for both I and II were linear for 0.01-0.5 mM and the detection limits were 3.5 µM-I and 3 µM-II. The RSD for the determination of 0.1 mM I or II were ±0.7 or ±0.35%, respectively. The method was applied to the analysis of pharmaceutical preparations. The method was also applicable to the determination of II in human urine following therapeutic administration of the drug.
Carbimazole Methimazole Spectrophotometry

"Determination Of Calcium In Water, Urine And Pharmaceutical Samples By Sequential Injection Analysis"
Anal. Chim. Acta 1996 Volume 323, Issue 1-3 Pages 75-85
J. F. van Staden* and R. E. Taljaard

Abstract: The sequential injection analysis is based on the fast complexation reaction between metalphthalein and Ca2+ followed by spectrophotometric detection at 573 nm. Plugs of 0.31 mL of water, 0.47 mL of 14% 2-amino-2-methylpropanol-1-ol buffer solution of pH 10.5, 0.23 mL of 0.0025% metalphthalein solution of pH 1.9 and 0.23 mL of sample were drawn at 4.68 ml/min into a holding coil (50 cm x 1.6 mm i.d.). The flow was then reversed and the stacked plugs were propelled through reaction coils (90 cm x 1.1 mm i.d. and 115 cm x 0.6 mm i.d.) to the flow-though detection cell (80 µL) where the absorbance was measured. A linear response was obtained for up to 20 mg/l of Ca and the detection limit was 0.05 mg/l. The RSD (n = 10) for 1-20 mg/l Ca were 0.66-0.85%. The method was applied to the determination of Ca in an effervescent tablet, tap water and urine, and the results were validated by AAS. The sampling frequency was 43 per h.
Calcium Spectrophotometry Sequential injection

"Sequential Injection Extraction For Sample Preparation"
Anal. Chim. Acta 1997 Volume 337, Issue 1 Pages 99-106
Kristina L. Petersona,*, Barry K. Loganb, Gary D. Christiana and Jaromir Ruzickaa

Abstract: A sequential injection extraction is presented based on the different flow velocities of aqueous and organic segments through a PTFE extraction coil (6 m x 0.8 mm i.d.) due to the hydrophobic interaction between the extraction coil and the organic segment. An air segment of 5 cm was inserted into the extraction coil followed by the organic segment and the aqueous segment. Air was then pumped into the coil to propel the aqueous segment through the organic segment which formed a coating on the inner walls of the coil. The flow direction was reversed and the aqueous segment was removed from the coil. The procedure was repeated with a second aqueous segment buffered at an optimal pH for back extraction. The technique was tested by extracting mixtures of barbiturates (as acid/neutral drugs) or serotonin re-uptake inhibitors (as basic drugs) from 500 µL urine using 50 µL butyl chloride/octanol (4:1) as the organic segment. The drugs were back extracted into 100 µL 0.45 M NaOH (for acidic/neutral drugs) or 0.18 M H3PO4 (for basic drugs) for analysis by HPLC. The absolute recoveries were 11-30% for urine samples spiked at the 50 µg/ml level. The sample throughput was 20/h.
Drugs Barbiturates Sample preparation Sequential injection Extraction Optimization

"Chemiluminescence Detection Of Porphyrins With The Peroxyoxalate Reaction By Flow Injection Analysis"
Anal. Chim. Acta 1997 Volume 339, Issue 1-2 Pages 131-138
Mei Lin and Carmen W. Huie*,*

Abstract: A flow injection chemiluminescence method was developed for determining porphyrins in biological fluids based on the reaction of bis-(2,4-dinitrophenyl) oxalate (DNPO) with H2O2. The detection cell allowed the DNPO reagent to be added to the carrier stream containing H2O2 and porphyrin at a position approximately 1 cm from the detection window. The chemiluminescence emission was detected with a photomultiplier tube via a 570 nm cut-off filter. The effects of pH, flow-rate and concentration of reagents on the chemiluminescence intensity were investigated. With the optimum conditions, viz. flow rate 1.25 ml/min, 1.5 mM DNPO, 3% H2O2 and pH 6, the calibration graphs for porphyrins were linear up to 1000 µg/ml. The recoveries for coproporphyrin from spiked urine were 97-98.2%. The method was applied to determine coproporphyrin in urine samples from healthy adults.
Porphyrins Chemiluminescence Optimization

"Chemiluminescent Flow Injection Determination Of Alkaline Phosphatase And Its Applications To Enzyme Immunoassays"
Anal. Chim. Acta 1997 Volume 339, Issue 1-2 Pages 139-146
Jin-Ming Lin, Akio Tsuji and Masako Maeda*

Abstract: The flow injection chemiluminescence method for determining alkaline phosphatase (ALP) was based on the catalyzed reaction of cortisol-21-phosphate to produce cortisol which was detected by its chemiluminescence reaction with lucigenin (NN'-dimethyl-9,9'-biacridinium dinitrate). Sample (100 µL) was injected into a Tris hydrochloride buffer carrier stream (0.5 ml/min) at pH 10 which was merged with the reagent stream (1.5 ml/min) containing 0.1 mg/mL lucigenin and 0.06% cetyltrimethylammonium bromide in 0.1 M NaOH. The chemiluminescence was detected using a photomultiplier tube. The calibration graph for 4-50 pM-ALP was presented. The detection limit was 1 pM-ALP and the RSD (n = 5) was <6.1%. The method was applied to FIA for 17-α-hydroxyprogesterone and human chorionic gonadotropin in urine or serum using ALP as the enzyme label. The results correlated with those obtained by other methods.
Enzyme, alkaline phosphatase 17-Hydroxyprogesterone Gonadotropin chorionic Chemiluminescence Immunoassay Catalysis Method comparison

"Stability Studies Of Arsenate, Monomethylarsonate, Dimethylarsinate, Arsenobetaine, Arsenocholine In Deionized Water Urine Clean-up Dry Residue From Urine Samples Determination By Liquid Chromatography With Microwave-assisted Oxidation-hydride Generation"
Anal. Chim. Acta 1997 Volume 340, Issue 1-3 Pages 209-220
M. A. Palaciosa,*, M. G&oacute;meza, C. C&aacute;maraa and M. A. L&oacute;pezb

Abstract: The stability of arsenate, monomethylarsonate, dimethylarsinate (DMA), arsenobetaine (AsB) and arsenocholine (AsC) at a concentration of 200 µg L-1 in deionized water, urine and dry clean-up residue of urine, stored in dark at -20°C, 4°C and ambient temperature, without the addition of any stabilizer reagent was evaluated. The five species were determined independently by liquid chromatography with microwave-assisted oxidation-hydride generation atomic absorption spectrometric detection. At -20°C, all species were stable in water and untreated urine; at 4°C and ambient temperature, they were stable during the 67 days of testing in the urine dry residue after the clean-up procedure. In untreated urine samples at 4°C and ambient temperature, AsC is unstable and easily transformed to the more oxidized species, AsB. In deionized water, AsB and AsC are transformed to other species such as DMA. The dry urine residue may be a good matrix as a reference material for As species.
Arsenate ion monomethylarsonic acid Dimethylarsinic acid Arsenoβine Arsenocholine HPLC Spectrophotometry Microwave Volatile generation Speciation Volatile generation

"Amperometric Biosensor For Uric Acid Based On Uricase-immobilized Silk Fibroin Membrane"
Anal. Chim. Acta 1998 Volume 369, Issue 1-2 Pages 123-128
Yu-Qing Zhang*, Wei-De Shen, Ren-Ao Gu, Jiang Zhu and Ren-Yu Xue

Abstract: An amperometric urate sensor based on a uricase-immobilized silk fibroin membrane and an O electrode in flow injection analysis are described. The biosensor shows that recoveries of uric acid in human serum and urine are at 94.2-102.6% and 92.5-97.9%, respectively. The relative standard deviations (RSDs) for repeatedly monitoring standard urate solution, human serum and urine are 2.37, 3.72 and 2.95%, respectively., based on 100 measurements. The urate sensor based on the uricase-immobilized membrane is capable of detecting 60-70 human serum samples per h. Also, a piece of uricase-immobilized fibroin membrane used at the sensor could not only be stored for over 2 yr, but also repeatedly monitored >1000 times for biosamples such as human serum or urine.
Uric acid Sensor Amperometry Electrode Immobilized enzyme Silk fibroin membrane

"Fluorimetric Determination Of Phenothiazine Derivatives By Photooxidation In A Flow Injection System"
Talanta 1994 Volume 41, Issue 11 Pages 1985-1989
Belkacem Laassisa, Jean-Jacques Aarona,* and Maria Carmen Mahederob,

Abstract: Flow-injection analysis (FIA) was combined with photochemically induced fluorescence (PF) detection for the determination of four phenothiazine derivatives, including unsubstituted phenothiazine, thionine, Azure A and Methylene Blue. The working analytical parameters (flow-rate, injected volume, photoreactor length) were optimized. Linear calibration graphs were obtained over about two orders of magnitude, with relative standard deviation within the range 1-2.3%. Limits of detection were between 13 and 35 ng/ml, according to the compound. The FIA-PF method was applied to the determination of phenothiazines in urine samples. Mean recoveries ranged from 94 to 117%.
Phenothiazine, derivatives Fluorescence Photochemistry

"Determination Of Nicotine By Reagent-injection Flow Injection Photometric Method"
Talanta 1998 Volume 47, Issue 4 Pages 833-840
Jingfu Liu* and Yingdi Feng

Abstract: Nicotine was determined by a reagent-injection flow injection photometric method making use of the Koing reaction. The applicability of four color reagents, aniline, barbituric acid, pyrazolone and sulfanilic acid, were evaluated and the sulfanilic acid was selected. The linear range, detection limit, RSD, and sample throughput of the established sulfanilic acid method were 0-10 mg L-1, 0.12 mg L-1, 0.7% and 50 h-1, respectively. Background absorption from sample matrix was eliminated by the reagent-injection flow injection technique. The proposed method was applied to determine nicotine in tobacco and urine samples with satisfactory results.
Nicotine Spectrophotometry Reverse Optimization

"Determination Of Vitamin C In Urine By Flow Injection Analysis"
Analyst 1986 Volume 111, Issue 2 Pages 167-169
Fernando L&aacute;zaro, Angel R&iacute;os, M. D. Luque de Castro and Miguel Valc&aacute;rcel

Abstract: Urine samples from individuals who had been given 0.5 g of ascorbic acid(I) were mixed with aqueous 0.05% oxalic acid and diluted with 5 volume of 0.9 M H2SO4. In a flow injection analysis method (see preceding abstract) the samples were mixed with chloramine T and KI - starch solution, and I was determined spectrophotometrically in the range 20 to 140 ppm. The procedure has advantages over existing manual and automated methods. The average recovery error was ±2.5%, with a sampling frequency of 90 samples h-1.
Ascorbic acid Clinical analysis Spectrophotometry Method comparison

"High Performance Liquid Chromatographic Determination Of 5-hydroxyindoles By Post-column Fluorescence Derivatization"
Analyst 1993 Volume 118, Issue 2 Pages 165-169
Junichi Ishida, Ryuji Iizuka and Masatoshi Yamaguchi

Abstract: A TSKgel ODS-80Tm column (15 cm x 4.6 mm; particle size 5 µm) was used with acetonitrile - 10 mM acetate buffer at pH 4.7 (1:19) as mobile phase (1.0 mL min-1) to separate the biogenic compounds 5-hydroxytryptophan (I), 5-hydroxytryptamine, 5-hydroxyindol-3-ylacetic acid (II), 5-hydroxytryptophol and N-acetyl-5-hydroxytryptamine (III). The eluate was reacted with 0.5 mL min-1 of a solution of 20 mM benzylamine and 3.0 mM KFe(CN)62- in acetonitrile - 25 mM borate buffer at pH 10 (1:1) in a PTFE coil (7 m x 0.5 mm) at 70°C and passed through a PTFE cooling coil (0.5 m x 0.5 mm) in ice-H2O before detection by fluorescence measurement with excitation at 345 nm and emission at 481 nm. Calibration graphs were rectilinear for up to at least 2.5 nmol of each amine; the detection limits ranged from 140 fmol of I to 470 fmol of III. The method was also used to determine II in urine samples from healthy and carcinoid human subjects (procedure detailed). A selective and sensitive high performance liquid chromatographic method with post-column fluorescence detection has been developed for the determination of 5-hydroxyindoles. Five biogenic 5-hydroxyindoles (5-hydroxytryptophan, 5-hydroxytryptamine, 5-hydroxyindol-3-ylacetic acid, 5-hydroxytryptophol and N-acetyl-5-hydroxytryptamine) were separated by isocratic elution on a reversed-phase column, TSKgel ODS-80Tm, and then converted into fluorescent derivatives by post-column reaction with benzylamine and potassium hexacyanoferrate(III) reagents. The detection limits (signal-to-noise ratio = 3) for the indoles were in the range 140-470 fmol per injection volume (100 µL). The method was applied to the determination of 5-hydroxyindol-3-ylacetic acid in human urine, with direct sample injection.
5-Hydroxytryptophan 5-Hydroxytryptamine 5-Hydroxyindole-3-acetic acid 5-Hydroxytryptophol N-Acetyl-5-hydroxytryptamine Fluorescence HPLC Post-column derivatization Heated reaction

"Arsenic In Ground Water In Six Districts Of West Bengal, India: The Biggest Arsenic Calamity In The World. 2. Arsenic Concentration In Drinking Water, Hair, Nails, Urine, Skin-scale And Liver Tissue Of The Affected People"
Analyst 1995 Volume 120, Issue 3 Pages 917-924
Dipankar Das, Amit Chatterjee, Badal K. Mandal, Gautam Samanta, Dipankar Chakraborti and Bhabatosh Chanda

Abstract: Hair (0.5-1 g) and nails (0.5 ng) were digested with HNO3 at 90-100°C for 5 min. Concentrated HNO3 was added and the solution was evaporated to 1 mL and diluted to 5 mL. Urine (1 ml) was heated with HNO3 and HClO4 until fumes were evolve and thus the flow injection thermospray system can be used over wide analytical ranges. Solutions containing up to 2% of NaCl could be injected without plugging of the thermospray vaporizer capillary.
Arsenic, total Arsenate ion Arsenite Dimethylarsinic acid monomethylarsonic acid Sample preparation Spectrophotometry

"Arsenic In Ground Water In Six Districts Of West Bengal, India: The Biggest Arsenic Calamity In The World. 1. Arsenic Species In Drinking Water And Urine Of The Affected People"
Analyst 1995 Volume 120, Issue 3 Pages 643-650
Amit Chatterjee, Dipankar Das, Badal K. Mandal, Tarit Roy Chowdhury, Gautam Samanta and Dipankar Chakraborti

Abstract: The As species present in the drinking water and urine of people in six districts of West Bengal affected by As-contaminated ground water were studied. The As species monitored were arsenite (I), arsenate (II), monomethylarsonic acid (III) and dimethylarsinic acid (IV). Four methods were used to determine I-IV in drinking water and/or urine: (i) separation of I and II from water with sodium diethyldithiocarbamate (NaDDTC) extraction followed by flow injection (FI) hydride-generation (HG) AAS determination; (ii) spectrophotometric determination of I and II from water with AgDDTC/CHCl3/hexamethylenetetramine as absorbing solution; (iii) separation of I-IV from water and urine by combined cation and anion-exchange resin columns followed by FI-HG-AAS determination; (iv) decomposition of total As in urine with HNO3/H2SO4/HClO4 followed by FI-HG-AAS. Results are discussed.
Arsenic, total Arsenate ion Arsenite Dimethylarsinic acid monomethylarsonic acid Spectrophotometry Spectrophotometry Sample preparation Extraction Method comparison Speciation Volatile generation Volatile generation

"Colloidal Gold Supported Onto Glassy Carbon Substrates As An Amperometric Sensor For Carbohydrates In Flow Injection And Liquid Chromatography"
Analyst 1996 Volume 121, Issue 2 Pages 249-254
Innocenzo G. Casella, Angelo Destradis and Elio Desimoni

Abstract: The cited sensor was prepared by depositing 10 µL 30 mM Au(III) on the surface of a vitreous C electrode. The electrode was dried and conditioned in 0.2 M NaOH by cycling the potential between -0.6 and 0.4 V vs. SCE for 30 min. The feasibility of using the Au-modified electrode as an amperometric sensor for carbohydrates was evaluated with a flow injection system, and the following LC method was developed for carbohydrate determination. The sample was analyzed on a Carbopac PA1 anion-exchange column (25 cm x 4 mm i.d.), with 0.2 M NaOH/1 µM-Au(III) as mobile phase (0.6 ml/min) and pulsed amperometric detection at dual Au-modified electrode, in serial configuration, held at 0.65 V vs. Ag/AgCl for 0.2 s, then at -0.7 V for 0.2 s and finally at 0.2 V for 0.4 s. Calibration graphs were linear over 2-3 orders of magnitude of concentration for the carbohydrates studied. Detection limits were 4-12 ng. RSD (n = 6) were 0.8-3.5%. The LC method was used to determine glucose in serum and urine. Recoveries of glucose were 97.7-102.1%. The results obtained agreed with those obtained by an enzymatic method.
Carbohydrates Glucose Amperometry HPIC Sensor Electrode Method comparison

"Miniaturized Graphite Sensors Doped With Metal-bathophenanthroline Complexes For The Selective Potentiometric Determination Of Uric Acid In Biological Fluids"
Analyst 1997 Volume 122, Issue 8 Pages 815-819
Saad S. M. Hassan and Nashwa M. H. Rizk

Abstract: Miniaturized poly(vinyl chloride) matrix membrane sensors in an all- solid-state graphite support, responsive to urate anion, were developed. The membranes incorporate lipophilic ion-pair complexes of urate anion with ruthenium(III), iron(II), nickel(II) and copper(I) bathophenanthroline (4,7-diphenyl-1,10-phenanthroline) counter cations. The sensors demonstrate a near-Nernstian response to urate over the concentration range 1 x 10^-2-1 x 10^-5 mol L-1 and have micromolar detection limits and good selectivity properties. The response is virtually unaffected by pH changes in the range 7-10 and the response times are 5-10 s in aqueous solutions and in human serum and urine samples. A flow injection detector incorporating an iron(II) bathophenanthroline-urate graphite sensor was used for continuous monitoring of uric acid. The minimum detectable concentration was approximately 8 µg mL-1 and the sample throughput was approximately 120 h-1. Direct potentiometric determination of uric acid in the static and hydrodynamic modes of operation over the range 15 µg mL-1-1.5 mg mL-1 showed average recoveries of 98.7 and 97.8% with RSDs of 0.6 and 0.7%, respectively. Application of the method to the determination of uric acid in human serum and urine gave results that compared favourably with those obtained by the standard spectrophotometric method.
Uric acid Potentiometry Electrode Electrode Electrode Sample preparation Sensor Detection limit Method comparison Process monitoring Ion pair extraction

"Electrooxidation Of Thiocyanate On Copper-modified Gold Electrode And Its Amperometric Determination By Ion Chromatography"
Analyst 1998 Volume 123, Issue 6 Pages 1359-1363
Innocenzo G. Casella*, Maria R. Guascito and Giuseppe E. De Benedetto

Abstract: Cyclic voltammetry was used to study the electrochemical behavior of an Au/Cu electrode towards the electrooxidn. of thiocyanate ion in alkaline medium. The effects of pH, Cu loading, scan rate and applied potential on the electrocatalytic oxidation of thiocyanate were studied. Flow injection experiments and ion-chromatography (IC) were performed to characterize the electrode as an amperometric sensor for the thiocyanate determination The effects of carbonate concentration. and common interferents on the retention time were also estimated. The electrode stability, precision, limit of detection and linear range were evaluated at a constant applied potential of 0.7 V vs. Ag/AgCl. Calibration plots, obtained in IC, were linear from 1.0 to 195 µM (correlation coefficient of 0.9984). The detection limit (LOD) was 0.5 µM (29 ppb) in a 50 µL injection. An example of anal. application, which includes the IC separation and detection of thiocyanate ion present in human urine, is given.
Thiocyanate ion Electrode Voltammetry HPIC Amperometry Apparatus Detector Interferences

"Speciation Determination Of Arsenic In Urine By High-performance Liquid Chromatography-hydride Generation Atomic Absorption Spectrometry With Online Ultraviolet Photooxidation"
Analyst 1998 Volume 123, Issue 8 Pages 1703-1710
Dimiter L. Tsalev, Michael Sperling and Bernhard Welz

Abstract: A coupled system for arsenic speciation determination based on high-performance liquid chromatography (HPLC), online UV photooxidation and continuous-flow hydride generation atomic absorption spectrometry (HGAAS) was built from commercially available modules with minor modifications to the electronic interface, the software and the gas-liquid separator. The best results were obtained with strong anion-exchange columns, Hamilton PRP X-100 and Supelcosil SAX 1, and gradient elution with phosphate buffers containing KH2PO4-K2HPO4. The online UV photooxidation with alkaline peroxodisulfate, 4% (m/v) K2S2O8-1 mol L-1 NaOH, in a PTFE knotted reactor for 93 s ensures the transformation of inorganic As(III), monomethylarsonate, dimethylarsinate, arsenobetaine, arsenocholine, trimethylarsine oxide and tetramethylarsonium ion to arsenate. About 32-36 HPLC-UV-HGAAS runs could be performed within 8 h, with limits of detection between 2 and 6 µg L-1 As, depending on the species. The method was applied to the analysis of spot urine samples and certified urine reference materials (CRMs). Upon storage at 4°C, reconstituted CRMs are stable for at least 2 weeks with respect to both their total arsenic content and the individual species distribution.
Arsenic(3+) Dimethylarsenic Monomethylarsine trimethylarsenic Tetramethylarsonium ion Arsenoβine Arsenocholine HPLC Spectrophotometry Spectrophotometry Photochemistry UV reactor Reference material Knotted reactor Volatile generation Speciation Phase separator

"Inductively Coupled Plasma Spectrometry In The Study Of Childhood Soil Ingestion. 2. Methodology"
J. Anal. At. Spectrom. 1989 Volume 4, Issue 8 Pages 727-735
Xioaru Wang, Alexandra L&aacute;sztity, Mikl&oacute;s Viczi&aacute;n, Yescheskel Israel and Ramon M. Barnes

Abstract: In a study aimed at quantifying the amount of soil ingested by infants and toddlers, faeces and urine collected in commodes or on diapers, together with home and pre-school dust, soil and food samples, were analyzed for Al, Ba, Mn, Si, Ti, V, Y and Zr by ICP-AES with multi-channel and sequential instruments, and V, Y and Zr were also determined by ICP-MS with flow injection sample introduction. Protocols are described for sample prep., and for online dilution and calibration for ICP-MS. Results obtained on standard solution and on reference soil and dust were in good agreement with certified or recommended values, and results by ICP-AES and ICP-MS were not statistically different, although those by ICP-MS were more precise. Flow injection ICP-MS is recommended for determining V, Y and Zr, which are present at low concentration.
Aluminum Barium Manganese Silicon Titanium Yttrium Sample preparation Spectrophotometry Mass spectrometry Reference material

"Merging Zones Flow Injection For The Determination Of Ultratraces Of Bismuth By Volatile Species Generation Atomic Absorption Spectrometry Using Sodium Tetraethylborate(III)"
J. Anal. At. Spectrom. 1998 Volume 13, Issue 5 Pages 431-435
J. Pablo Valles Mota, M. Rosario Fern&aacute;ndez de la Campa and Alfredo Sanz-medel

Abstract: The generation of a volatile Bi compound by its reaction in aqueous solution with sodium tetraethylborate(III) has been achieved using a flow injection (FI) system with injection of Bi and NaBEt4 solutions in a 'merging zones' mode. This vapor generation (VG) system has been successfully interfaced with an atomic absorption spectrometric (AAS) detector for the determination of low levels of the metal. A detection limit of 0.8 µg L-1 (0.56 ng) of Bi was obtained after optimization of the chemical and instrumental parameters. This volatile species generation with AAS detection showed a precision of ±2.9% at the 40 µg L-1 level of Bi and a sample throughput of about 100 samples h-1 was observed Interference studies were carried out for many potentially interfering elements. The proposed FI-VG-AAS method proved to be very selective for the determination of Bi and so it has been successfully applied to the determination of ultratraces of Bi in human urine after simple 1+1 dilution without any other pretreatment; the detection limit in real urine samples was 1.6 µg L-1. Bismuth recoveries of 100% were found in spiked urine samples and also excellent agreement was achieved between results obtained by FI-VG-AAS and those obtained by ICP-MS for real urine samples. Finally, the proposed procedure was applied to the study of urinary clearance of Bi in three different people after intake, at therapeutic doses, of colloidal Bi subcitrate (CBS).
Bismuth Spectrophotometry Interface Interferences Volatile generation Method comparison Merging zones

"Vesicle-assisted Determination Of Ultratrace Amounts Of Cadmium In Urine By Electrothermal Atomic Absorption Spectrometry And Inductively Coupled Plasma Mass Spectrometry"
J. Anal. At. Spectrom. 1998 Volume 13, Issue 9 Pages 899-903
Heidi Goenaga Infante, Maria L. Fern&aacute;ndez S&aacute;nchez and Alfredo Sanz-medel

Abstract: Two methods for the determination of ultratrace amounts of Cd, based on vesicular hydride generation, including in situ trapping electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICP-MS), are described and compared for Cd determination in urine. The human urine samples are diluted 1 + 1 with ultrapure water and no other sample pre-treatment is necessary. Thus, the risk of contamination at basal or 'normal' metal levels in urine is minimized. Using flow injection hydride generation ICP-MS (FI-HG-ICP-MS), the detection limits observed for Cd in water and urine (50 µL sample volume) were 3.5 and 7 pg, respectively, the observed relative standard deviation for ten replicate analyzes of 50 µL of a 5 µg L-1 aqueous CD solution was ±3.2%. In situ trapping allows pre-concentration. in the graphite tube; by pre-concentrating. 1.4 mL of urine the detection limit achieved by ETAAS was 10 ng L-1 (14 pg, abs.). The use of silicone as an antifoam agent for vesicular cadmium hydride generation allowed a throughput of about 20 samples h-1 by FI-HG-ICP-MS detection. The concentration. of Cd in human urine was evaluated directly by aqueous standard calibration as no matrix interferences were observed for both methods under study. NIST SRM 2670 Toxic Metals in Freeze-Dried Urine was analyzed by the two methods with excellent results. The accuracy of the results was demonstrated in two ways because the reported values for the SRM agreed well with the results obtained using either of the two methods under investigation.
Cadmium Spectrophotometry Mass spectrometry Reference material Interferences Method comparison Vesicle

"Cobalt(II)-catalyzed Chemiluminescence In A Dioctadecyldimethylammonium Chloride Bilayer Membranous Medium For The Flow Injection Determination Of Phenylpyruvic Acid"
Anal. Chem. 1991 Volume 63, Issue 20 Pages 2301-2305
Mari Kishida, Yuji Makita, Takehiko Suzuki, Masaaki Yamada, and Toshiyuki Hobo

Abstract: A novel chemiluminescence system is described for the flow injection determination of phenylpyruvic acid (PPA). The presence of both ordered surfactant molecular assemblies and a metal ion catalyst in the system is essential for the phosphorescence of benzaldehyde (emitter) produced by the aerobic oxidation of PPA in alkaline solution. Dioctadecyldimethylammonium chloride bilayer aggregates and cobalt (II) allows PPA to be selectively determined down to 1 X 10^-7 M. The linearity is 2 orders of magnitude with a relative standard deviation 3.1% (n = 10) for 1 X 10^-6 M PPA. Of 28 other species (1 X 10^-3 M) tested, only 4-hydroxymanderic acid, 4-hydroxyphenylpyruvic acid, 2,5-dihydroxyphenylacetic acid, and 4-hydroxy-3-methoxyphenylpyruvic acid provided signals 2-13 times more intense than that for 1 X 10^-6 M PPA. PPA present at 10^-3 - 10^-2 M levels in urine from patients with phenylketonuria can be determined with no special sample pretreatment by using this CL procedure. The mechanistic study of the present luminescent reaction are also undertaken in detail. The bilayer aggregates were found to contribute favorably both to the production of key intermediates and to the efficient phosphorescence emission. A chemiluminescence system capable of directly determining phenylpyruvic acid (I) in urine is described. The method is based on measurement of the chemiluminescence arising from the oxidation of I by dissolved O in an alkaline solution containing dimethyldioctadecylammonium chloride (II) bilayer membranous aggregates in the presence of Co(II) as catalyst. Sample (170 µL) was injected into a flow system (2.2 mL min-1) of 10 µM-CoCl2 and a mixed solution of 1 mM II - 10 mM NaOH, and a Lumiflow 1000 luminometer was used. I is selectively determined down to 0.1 µM. The coefficient of variation was 3.1% (n = 10) for 1 µM-I. I present at 1 to 10 mM levels in urine from patients with phenylketonuria was determined with no special sample pre-treatment.
Phenylpyruvic acid Chemiluminescence Phosphorescence Catalysis Surfactant

"Kinetic Flow Injection Spectrofluorimetric Determination Of Aluminum(III) Using Eriochrome Red B, Sensitized By Traces Of Fluoride"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 2 Pages 204-207
F. Carrillo, C. P&eacute;rez-Conde, C. C&aacute;mara

Abstract: Samples (100 µL) containing 1000 µg/l Al were injected into a carrier stream of 0.01 M NaF (0.45 ml/min) and mixed with 1.5 M hexamethylenetetramine (HMTA) buffer of pH 6 in a stream of HClO4 (0.6 ml/min) in a reaction coil (50 cm). The mixed solution was subsequently mixed with a 0.1% Erichrome Red B solution (0.45 ml/min) in a second reaction coil (500 cm x 0.5 mm i.d.) at 80°C and cooled to 4°C in a third reaction coil. The fluorescence intensity of the resultant solution was measured in a 18 µL flow cell (10 mm light-path) at 595 nm (excitation at 470 nm). The calibration graph was linear up to 1000 µg/l of Al with RSD (n = 10) of 2.6, 2.2 and 2%, respectively, for 5, 20 and 50 µg/l of Al, respectively. The detection limit was 0.15 µg/l in the presence of fluoride. Potential interferent anions and cations (listed) were studied with 20 µg/l Al; FIA was more selective than a batch procedure and more tolerant of Fe(III). The procedure was used successfully to determine Al in tap water, mineral water or urine.
Aluminum(III) Fluorescence Interferences Kinetic

"Determination Of Total Arsenic In Urine By Hydride AAS After UV-digestion"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 7-8 Pages 838-843
R. Ritsema and E. van Heerde

Abstract: A method for analyzing arsenic in urine samples by Flow Injection Analysis-Atomic Absorption Spectrometry (FIA-AAS) after ultra-violet (UV) digestion is developed and validated. The validated method has the following performance characteristics: limit of detection (LOD) 0.5 µg L-1, repeatability and reproducibility better than 5% and 10% relative standard deviation (RSD) respectively for arsenic concentrations above 3 µg L-1, linear range 0.5-40 µg L-1. Validation of the method was performed by analyzing several certified reference materials. Results obtained were well within the certified intervals. Several urine samples analyzed by UV-FIA-AAS were also analyzed by Inductively Coupled Plasma-Mass Spectrometry after High Performance Liquid Chromatography (HPLC-ICP-MS) in order to investigate comparability. Again results were satisfactory, arsenic concentrations in urine samples did not differ from each other significantly. Storage conditions were also studied. Urine samples are best stored in polyethylene containers at 5 ± 4°C and are stable in arsenic content for at least 30 days.
Arsenic, total Spectrophotometry Sample preparation UV reactor Photochemistry

"Determination Of Toxic And Non-toxic Arsenic Species In Urine By Microwave-assisted Mineralization And Hydride-generation Atomic Absorption Spectrometry"
Microchim. Acta 1995 Volume 120, Issue 1-4 Pages 301-308
M. Angeles L&oacute;pez-Gonz&aacute;lvez, M. Milagros G&oacute;mez, Carmen C&aacute;mara and M. Antonia Palacios

Abstract: Human urine (100 µL) was injected into a stream (0.7 ml/min) of water which merged with a stream (4.6 ml/min) of 5% K2S2O8/5% NaOH and passed to a PTFE coil (1.5 m x 0.5 mm i.d.) inside a microwave oven operated at 700 W. The oven outflow was cooled in PTFE tubing (0.5 m x 0.5 mm i.d.) in an icebath, then mixed with 4 M HCl (1.9 ml/min) and 3% NaBH4 (1.9 ml/min) and the generated arsine was separated in a gas-liquid separator and carried in Ar (10 ml/min) to the AAS system for determination of total As. Total toxic As [arsenite, arsenate, monomethylarsenic (MMA), dimethylarsenic (DMA)] was determined as above but with use of 1 M HCl (1.9 ml/min) instead of K2S2O8 and blocking of the 4 M HCl channel. Calibration graphs were linear for 2-20 ng As as As(V), arsenobetaine, arsenocholine, MMA or DMA and the detection limits were 4 and 6 µg/l with and without K2S2O8 respectively; the corresponding RSD (n = 10) were 7% and 4% for 100 µg/l arsenate. The analysis time was 20 s. Flow injection - microwave oven - hydride generation - atomic absorption spectroscopy (FI-MO-HG-AAS) has been optimized for the determination of the total and toxic arsenic in urine with and without persulfate, respectively. With microwave oven assisted digestion of urine with 5% (w/v) K2S2O8 and 5% (w/v) NaOH all arsenicals completely can be converted to arsenate, which is determined by HG-AAS to give the total concentration of the six species present in urine. The detection limits of 4-6 µgl-1, the relative standard deviation of 3-7% and the high sample throughput make the methods suitable for rapid routine online determination. Application of the proposed procedures to the analysis of urine from people on a diet rich in seafood revealed a significant increase in total urinary arsenic due to the rapid excretion of organoarsenicals. Efficient decomposition and quantitative recovery of all arsenic species in spiked urine is achieved by using 5% K2S2O8 in 5% NaOH at 4.6 mL min-1, microwave power of 700 W and a 1.5 m coil. (20 references)
Arsenate ion Arsenic(5+) Arsenite Arsenoβine Arsenocholine monomethylarsonic acid Dimethylarsinic acid Sample preparation Spectrophotometry Microwave Online digestion Speciation Phase separator Volatile generation Volatile generation

"Flow Injection Potentiometry For The Assay Of Potassium In Biological Fluids"
Microchem. J. 1992 Volume 45, Issue 2 Pages 232-247
Judit Jeney, Kl&aacute;ra T&oacute;th*, Brno Lindner and Ern Pungor

Abstract: Potassium-selective solvent polymeric membranes (PVC and modified PVC) were made with the use of various ionophores, and discs of the membranes (7 mm diameter) were mounted in a commercially available electrode body. The performance characteristics were evaluated by the use of KCl solution, blood serum, and urine-like electrolytes, and a macro wall-jet potentiometric detector was designed (description given) for the determination of K in undiluted urine samples (using a flow injection technique). A carrier solution of 1 mM KCl, 130 mM MgCl2 and 24.8 mM Tris (adjusted to pH 8) was selected. Within-run precision of the analytical data (relevant to urine samples) in comparison with data obtained by the batch operation mode and by a commercial continuous-flow ion-analyzer (SERA 210) are presented in diagrammatic form. A correlation study is also presented relating to the potassium concentration. of undiluted urine obtained by the flow injection technique, the continuous-flow method (SERA 210) and flame AES. The performance characteristics (selectivity, slope of the electrode response, response time) of poly(vinyl chloride and modified poly(vinyl chloride)-based solvent polymeric, K-selective membrane electrodes were evaluated in relevance to the anal. of ionic constituents in biological samples. A flow injection system incorporating a macro wall-jet potentiometric detector was designed and its utility for the K assay in undiluted urine samples was evaluated. Anal. data obtained by flow methods for K content of patients' blood serum and urine samples had been correlated with flame atomic emission spectrometric data.
Potassium Potentiometry Electrode Method comparison

"KMnO4-octylphenyl Polyglycol Ether Chemiluminescence System For Flow Injection Analysis Of Uric Acid In Urine"
Microchem. J. 1998 Volume 59, Issue 2 Pages 278-283
Zheng Li, Manliang Feng and Jiuru Lu

Abstract: A fast and simple KMnO4-octylphenyl polyglycol ether (OP) chemiluminescence system for flow injection analysis of uric acid is described. When a mixture of sample and OP is injected into acidic KMnO4 solution in a flow cell, strong chemiluminescence occurs. The response is linear to the concentration. of uric acid in the range 0.10 to 600 µg mL-1 with different permanganate concentrations. The relative standard deviation of the method is between 1.7 and 3.1 %. The detection limit is 0.055 µg mL-1. Most common substances in biological samples did not interfere, except ascorbic acid, which should be spoiled with Fe(III). The results can be obtained within 1 min for each measurement. The recommended method has been successfully tested for determination of uric acid in human urine. Chemiluminescence intensity was found to be remarkably enhanced in the presence of the OP micellar system. (c) 1998 Academic Press.
Uric acid Chemiluminescence Interferences Indirect Micelle

"High Performance Liquid Chromatographic Determination Of Catecholamines And Their Precursors And Metabolites In Human Urine And Plasma By Post-column Derivatization Involving Chemical Oxidation Followed By Fluorescence Reaction"
Anal. Biochem. 1992 Volume 200, Issue 2 Pages 332-338
Hee-Kyoung Jeon, Hitoshi Nohta and Yosuke Ohkura

Abstract: Urine or plasma was mixed with isoproterenol and 3,4-dihydroxyphenylpropionic acid (internal standards) and HClO4. After centrifugation, the supernatant solution was adjusted to pH 1.5 to 2.0 with 2 M K carbonate and centrifuged. The supernatant solution was applied to a Toyopak IC-SP S cartridge, eluted with 1.5 M KCl in 100 mM HCl - methanol (93:7; for urine) or 2 M NaClO4 - methanol (93:7; for plasma). Eluates were analyzed by HPLC (cf. Anal. Sci., 1991, 7, 257). The calibration graphs were rectilinear for 2 to 1000 pmol of L-dopa and 0.2 to 200 pmol for other catecholamines. The coefficient of variation were 1.9 to 5.4 and 3.2 to 7.3% for urine and plasma, respectively. Detection limits were from 0.5 to 95 pmol mL-1.
Catecholamines HPLC Fluorescence Post-column derivatization

"Determination Of Ascorbic Acid In Human Urine By High Performance Liquid Chromatography Coupled With Fluorimetry After Post-column Derivatization With Benzamidine"
J. Chromatogr. A 1987 Volume 385, Issue 1 Pages 287-291
Tokuichiro Seki and Yoshihisa Yamaguchi, Kohji Noguchi and Yuzo Yanagihara

Abstract: Urine was mixed with an equal volume of 5% H3PO4 containing 0.5% of thiodiethanol(I) and a portion (1 ml) was filtered through a cooled column (10 cm x 7 mm) of Dowex 50W-X8 (200 to 400 mesh; H+). Elution was carried out with 2 mM tartaric acid containing 0.05% of I, the eluate was filtered (0.45 µm), and a portion (50 to 250 µL) was analyzed on two columns (50 cm x 7.6 mm), at 30°C, packed with Asahipak GS-320 and connected in series. The mobile phase (1 mL min-1) was tartaric acid (4.5 g), Na2EDTA (1.5 g) and I (1 g) dissolved in water (2 l) and adjusted to pH 3.00 to 3.03 with 4 M NaOH. Post-column derivatization was achieved at 90°C with 20 mM benzamidine in 0.75 M potassium phosphate (pH 10) followed by fluorimetric detection at 400 nm (excitation at 325 nm). The separation of glucose, dioxogulonic acid plus dioxogluconic acid, dehydroisoascorbic acid, dehydroascorbic acid, ascorbic acid and isoascorbic acid, was achieved in 55 min. The recoveries of ascorbic acid and isoascorbic acid at concentration. of 10 and 50 µM, respectively, were 98.2 ± 1.7% and 98 ± 1.5%. The correction procedures required to compensate for conversion effects on the column are discussed.
Ascorbic acid isoascorbic acid HPLC Fluorescence Heated reaction Post-column derivatization

"Determination Of Pseudouridine In Human Urine And Serum By High Performance Liquid Chromatography With Post-column Fluorescence Derivatization"
J. Chromatogr. A 1990 Volume 515, Issue 1 Pages 495-501
Yoshihiko Umegae, Hitoshi Nohta and Yosuke Ohkura

Abstract: Urine (100 µL) was mixed with 100 µL of 0.5 mM 5-fluorouridine (I; internal standard) and 800 µL of water. Serum (0.5 ml) was mixed with 0.5 mL of 0.05 mM I and 0.5 mL of 2 M HClO4, and the mixture was centrifuged at 1000 g and 4°C for 10 min. The supernatant solution (0.5 ml) was mixed with 65 µL of 2 M K2CO3 and re-centrifuged. An aliquot (100 µL) of either solution was analyzed by HPLC on a column (15 cm x 4.6 mm) of TSK gel ODS-80 (5 µm), with 2 or 4% of methanol in 10 mM phosphate (pH 5.0) as mobile phase (0.5 mL min-1). Detection was at 254 nm, and, after mixing the eluate with 2 mM NaIO4 and 20 mM 1,2-bis-(4-methoxyphenyl)ethylenediamine (each at 0.25 mL min-1), by fluorimetry at 470 nm (excitation at 340 nm). Calibration graphs were rectilinear for 0.5 to 50 nmol of pseudouridine in 100 µL of urine or 0.1 to 4 nmol of I in 0.5 mL of serum. Limits of detection were 40 and 8 nM, respectively.
Pseudouridine HPLC Fluorescence Post-column derivatization Column pH Calibration Detection limit

"Determination Of Citrulline And Homocitrulline By High Performance Liquid Chromatography With Post-column Derivatization"
J. Chromatogr. B 1990 Volume 497, Issue 1 Pages 37-43
Ichiro Koshiishi, Yumiko Kobori and Toshio Imanari

Abstract: For determination of citrulline (I) in plasma, samples were extracted with trichloroacetic acid and subjected to HPLC on a column (15 cm x 4 mm) of TSK gel SCX with 50 mM citrate buffer containing 0.3 mM NaCl as mobile phase (0.4 mL min-1). The post-column colorimetric reaction was carried out with phthalaldehyde and N-(1-naphthyl)ethylenediamine; detection was at 520 nm. For homocitrulline (I) in urine, acidified samples were applied to a column of Amberlite CG-120 (H+ form) cation exchange resin; II was eluted with 0.1 M Tris - HCl buffer and subjected to HPLC as described. Both I and II were well separated with no interference from protein amino-acids or urea. Calibration graphs were rectilinear in the ranges 2.6 to 500 and 4.3 to 500 µM, respectively. Results indicated that the level of I in the plasma of uremia patients is higher than that in healthy plasma, and that II is excreted into healthy human urine but not into plasma.
Citrulline Homocitrulline HPLC Post-column derivatization Buffer Calibration Interferences Amberlite

"High Performance Liquid Chromatographic Method For Post-column, Inline Derivatization With O-phthalaldehyde And Fluorimetric Detection Of Phenylpropanolamine In Human Urine"
J. Chromatogr. A 1984 Volume 284, Issue 2 Pages 457-461
Daniel Dye and Thomas East, William F. Bayne

Abstract: A mixture of 2 mL of urine and 40 µg of amphetamine (internal standard) was centrifuged. A 25 µL portion of the supernatant liquid was injected into a stainless-steel column (12.5 cm x 4.6 mm) packed with ODS-Hypersil (5 µm) and equipped with a stainless-steel guard column (3 cm x 4.6 mm) packed with LiChrosorb ODS (10 µm). The mobile phase (1.5 mL min-1) was 0.05 M NaH2PO4 - 0.01 M Na hexanesulfonate - 7.2 mM triethylamine adjusted to pH 3 with H3PO4 and containing 40% of methanol. A borate-buffered phthalaldehyde reagent of pH 10.4 (prep. described) was introduced into the eluent from the analytical column at 1.5 mL min-1. The mixture flowed through a PTFE coil (4.8 m x 0.7 mm), forming an inline reactor, to a spectrofluorimeter for detection of the phenylpropanolamine derivative at 418 nm (excitation at 340 nm). The coefficient of variation (n = 5) at 0.96, 3.82, 9.55, 38.2 and 96 µg mL-1 were 2.23, 0.55, 0.41, 0.64 and 0.19%, respectively. The limit of detection was 0.1 µg mL-1 in urine.
Phenylpropanolamine HPLC Fluorescence Post-column derivatization

"Fluorimetric Determination Of Catecholamines Using Glycylglycine As The Reagent For Post-column Derivatization"
J. Chromatogr. A 1984 Volume 287, Issue 2 Pages 407-412
Tokuichiro Seki and Yoshihisa Yamaguchi

Abstract: Catecholamines were extracted from human urine, containing isoprenaline as internal standard, on a column of Amberlite CG-50; elution was effected with 0.66 M H3BO3, and a portion of the eluate at pH 4.0 was analyzed on a column (30 cm x 8 mm) of Amberlite IRC-50 with 0.5 mM Na2EDTA in 0.35 M H3BO3 - 0.12 M tartaric acid buffer solution of pH 4 as mobile phase (1 mL min-1). The eluate was treated with a 1.5% solution of glycylglycine in 0.05 M H3BO3 (2 mM in ZnSO4), followed by potassium borate buffer solution (pH 9.4) containing 0.01% of Fe(CN)63- as catalyst. The resulting derivatives were determined fluorimetrically at 500 nm (with excitation at 350 nm). Calibration graphs were rectilinear in the range 1 to 100 ng. Adrenaline, noradrenaline and dopamine were well resolved in ~30 min, and recovery of all compounds studied was almost quantitative.
Catecholamines Adrenaline Noradrenaline Dopamine Ion exchange Fluorescence Amberlite Post-column derivatization

"Post-column Reaction Of Amino-acids With The Pentane-2,4-dione - Formaldehyde System For Their Automated Analysis"
J. Chromatogr. A 1985 Volume 318, Issue 2 Pages 367-372
Kazuaki Kakehi, Tadao Konishi, Ikuo Sugimoto and Susumu Honda

Abstract: The amino-acid sample is separated on a glass column (40 cm x 9 mm) packed with Hitachi 2611 resin with gradient elution from 0.2 M citrate buffer (pH 3.25) to 1.2 M citrate buffer (pH 5.28) at a flow rate of 1.0 mL min-1. The eluate is treated with 6% pentane-2,4-dione solution and 9% formaldehyde solution, both in 1 M acetate buffer (pH 6.22) in a PTFE coil (30 m x 0.5 mm) at 95°C, and the fluorescent reaction products are detected at 476 nm (excitation at 417 nm). The detection limits for glycine(I) and lysine(II) are 342 and 267 pmol, respectively; calibration graphs are rectilinear for 5 to 500 nmol of serine, I or II, and the coefficient of variation (at 50 nmol) are <5%. The method was applied to a nutritional drink, chymotrypsinogen and insulin acid hydrolysates and normal human urine.
Amino Acids Glycine Lysine HPIC Fluorescence Heated reaction Post-column derivatization Resin

"Improved High Performance Liquid Chromatographic Method For The Determination Of 6-N,N,N-trimethyl-lysine In Plasma And Urine: Biomedical Application Of Chromatographic Figures Of Merit And Amine Mobile Phase Modifiers"
J. Chromatogr. B 1986 Volume 380, Issue 2 Pages 285-299
Paul E. Minkler, Elizabeth A. Erdos, Stephen T. Ingalls, Ronda L. Griffin and Charles L. Hoppel

Abstract: Samples of blood and urine were collected from rats and human subjects; the urine samples were hydrolyzed with concentrated HCl at 105°C for 18 h. The hydrolysate or blood plasma samples were purified on successive columns (3.5 cm x 5 mm) of Dowex 50-X8 (NH4+ form) and Dowex 1-X8 (OH- form), respectively; elution was effected with aqueous 2.2 M NH3. The eluate was analyzed by HPLC on a cartridge (10 cm x 5 mm) of Radial-Pak C18 (10 µm) equipped with a pre-column (5 cm x 4 mm) of Co:Pell ODS; the mobile phase consisted of 2.5 mM Na dodecyl sulfate - 30 mM NaH2PO4 - 20 mM 3-(dimethylamino)propane-1,2-diol in acetonitrile. Post-column derivatization was carried out by treating the eluate with phthalaldehyde - 2-mercaptoethanol in 0.5 M H3BO3. Detection was by fluorimetry at 418 nm (excitation at 240 nm). The detection limit was 0.2 nmol mL-1 of analyte. The effect of pH of the mobile phase on the performance of the system was investigated.
6-N,N,N-Trimethyllysine HPLC Fluorescence Optimization Post-column derivatization

"Detection And Quantitation Of Gadolinium Chelates In Human Serum And Urine By High Performance Liquid Chromatography And Post-column Derivatization Of Gadolinium With Arsenazo III"
J. Pharm. Biomed. Anal. 1995 Volume 13, Issue 7 Pages 927-932
Erlend Hvattum*, Per Trygve Normann, Gene C. Jamieson, Jan-Ji Lai and Tore Skotland

Abstract: A narrow-bore high performance liquid chromatography method was developed for simultaneous separation of gadolinium diethylenetriaminepentaacetic acid (GdDTPA), the monomethylamide (GdDTPA-MMA) and the bis-methylamide (GdDTPA-BMA) in human serum and urine. The Gd complexes were detected at 658 nm after post-column derivatization with Arsenazo III. The serum samples were ultrafiltrated, whereas the urine samples were centrifuged and diluted before analysis. With an injection volume of 10 µL on a 2.1 mm ID reversed-phase column, the limit of detection of GdDTPA-BMA was calculated as 0.3 µM and 1.1 µM in serum and urine, respectively. The method was validated with respect to GdDTPA-BMA with a limit of quantification set to 2 µM and 10 µM in serum and urine, respectively. The best fit of the calibration curve was obtained using non-linear regression according to the equation Y = A+BX+CX2 in the concentration ranges 2-800 µM and 10^-2000 µM of GdDTPA-BMA in serum and urine, respectively. The precision of the method was found to range from 1 to 4% RSD. The recoveries of GdDTPA-BMA spiked in serum and urine were higher than 95% with an RSD equal to or less than 4%. The serum samples were stable for at least 5 months when stored at -70°C, and the urine samples were stable for a least 6 months when stored at -20°C.
Gadolinium diethylenetriamine pentaacetic acid Gadolinium monomethylamide Gadolinium bis-methylamide HPLC Spectrophotometry Post-column derivatization

"Spectrophotometric Methods For The Determination Of Cephradine Or Ceftazidine In Human Urine Using Batch And Flow Injection Procedures"
J. Pharm. Biomed. Anal. 1997 Volume 15, Issue 11 Pages 1687-1693
V. R&oacute;denas, M. S. Garc&iacute;a, C. S&aacute;nchez-Pedre&ntilde;o* and M. I. Albero

Abstract: Sensitive and fast spectrophotometric methods for the determination of cephradine or ceftazidine in human urine, based on the formation of compounds between these drugs and Pd(II), are described. In the batch procedures the calibration graphs resulting from the measurement of the absorbance at 330 nm is linear over the range 5.0-60.0 µg mL-1 for cephradine and 3.0-60.0 µg mL-1 for ceftazidine. The methods were successfully adapted to FI-systems, the peak heights being proportional to cephalosporin concentration over the range 5.0-60.0 µg mL-1 for cephradine and 3.0-60.0 µg mL-1 for ceftazidine. The sampling frequency was 60 h-1 with a sample injection of 72 µL.
Ceftazidime Cephalosporin C Spectrophotometry Method comparison

"High Performance Liquid Chromatographic Determination Of Acidic Catecholamine Metabolites In Human Urine Using Post-column Fluorescence Derivatization With Dl-1,2-diphenylethylenediamine"
Anal. Sci. 1990 Volume 6, Issue 5 Pages 677-682
H.-K. JEON, H. NOHTA and Y. OHKURA

Abstract: Urine was diluted 5-fold with water, ultra-filtrated, and 3,4-dihydroxymethoxymandelic acid, 4-hydroxy-3-methoxy- and 3,4-dihydroxy-phenylacetic acid and 4-hydroxy-3-methoxymandelic acid were determined by HPLC on a column (25 cm x 4.6 mm) of TSK gel DEAE-2SW anion-exchange gel (5 µm) with 25 mM NaH2PO4 (pH 3.0) - 70 µM-Na2EDTA containing 30% of acetonitrile as mobile phase (1 mL min-1) and electrochemical detection at 0.5 V vs. Ag - AgCl. The eluate was mixed with 40 mM dl-1,2-diphenylethylenediamine in propan-2-ol and 50 mM Na methoxide in propan-2-ol (0.4 mL min-1), the mixture was passed through a reaction coil (10 m x 0.5 mm) at 110°C. After cooling the fluorescence was monitored at 515 nm (excitation at 420 nm). The detection limits were 15 to 20 fmol. The method was 20-times more sensitive to 3,4-dihydroxymandelic acid than methods using meso-1,2-diphenylethylenediamine and did not require complicated sample cleanup.
Catecholamines HPLC Fluorescence Post-column derivatization Dilution Column Detection limit

"Optimization Of Microwave Digestion For Determination Of Selenium In Human Urine By Flow Injection-hydride Generation-atomic Absorption Spectrometry"
Anal. Commun. 1998 Volume 35, Issue 11 Pages 361-364
Fangshi Li, Walter Goessler and Kurt J. Irgolic

Abstract: A microwave digestion program, which completely decomposes and oxidizes selenium compounds in urine to selenate, was developed by monitoring the pressure and the temperature during microwave digestion. The efficient decomposition and quant. recovery of trimethylselenonium iodide spiked into urine was achieved in 18 min using the optimized microwave program reaching 200°C and 8 bar. The selenate in the digest was reduced to selenite by hydrochloric acid with the aid of microwave energy. Urea was found useful to eliminate NOx fumes, which might be absorbed in the digest and interfere in the determination of selenium by flow injection-hydride generation-at. absorption spectrometry (FI-HG-AAS). The recovery of trimethylselenonium iodide, selenomethionine, selenoethionine added to urine was 96.5-105%. The whole procedure, FI-HG-AAS determination following microwave digestion of urine sample and microwave reduction of selenate in the digests into selenite, was checked with two Standard Reference Materials 2670 (toxic metals in human urine). The results showed good agreement with the certified values (normal level 30 ± 8 µg Se L-1 and elevated level 460 ± 30 µg Se L-1). The detection limit of the whole procedure was 3 µg Se L-1 urine. Selenomethionine and selenoethionine were found unstable during the microwave heating used to reduce selenate to selenite. Such a microwave reduction procedure should be cautiously used to distinguish selenate from selenite in the matrixes which might contain organic selenium compounds
Selenium Trimethylselenium Selenomethionine Selenoethionine Spectrophotometry Sample preparation Interferences Reference material Optimization

"Flow Injection Fluorometric Analysis Of Several Aminophenothiazines Based On Photooxidation"
Analusis 1997 Volume 25, Issue 6 Pages 183-188
LAASSIS B.; AARON J.J.

Abstract: Flow injection analysis (FIA) was combined with photochemically induced fluorescence (PIF) detection for the determination of four aminophenothiazines, including ethopropazine, trifluoperazine, levomepromazine and thioproperazine. The working analytical parameters (flow-rate, injected volume, photoreactor length) were optimized. Linear calibration curves were obtained over about two orders of magnitude, with relative standard deviations within the range 1.2-4.5%. Limits of detection and quantification were, respectively, between 60-90 and 200-400 ng.mL-1, according to the compound. The FIA-PIF method was applied to the determination of aminophenothiazines in urine samples and pharmaceutical preparations. Mean recoveries ranged from 87 to 118%, according to the compound. 33 References
Aminophenothiazines Ethopropazine Trifluoperazine Levomepromazine Thioproperazine Drugs Fluorescence Optimization

"Thermospray Liquid Chromatography - Mass Spectrometry Of Polar β-blocking Drugs: Preliminary Results"
Biol. Mass Spectrom. 1991 Volume 20, Issue 10 Pages 647-649
M. S. Leloux, W. M. A. Niessen, R. A. M. van der Hoeven

Abstract: The influence of either vaporizer temperature (90 to 120°C) or repeller potential on analyte signals and mass spectra of five β-blocking drugs was investigated by delivering the compounds (200 ng) to a thermospray interface to a triple quadrupole mass spectrometer using flow injection analysis in a stream (1.2 mL min-1) of methanol - 50 mM ammonium acetate (1:1) adjusted to pH 3.0 with formic acid. The fragmentation patterns were strongly dependent on the instrumental parameters which were optimized at 100°C and 50 V for vaporizer temperature and repeller potential, respectively. For LC - MS studies aqueous solution of atenolol (0.2 to 200 ng) and propafenone (200 ng), used as internal standard, were delivered to the interface by HPLC on a column (10 cm) packed with Nova-Pak CN-HP (4 µm) and operated with the same mobile phase but in the ratio 2:3. Absolute detection limits for atenolol were 0.2 ng using selected ion monitoring of m/e 267 or 2 ng for full-scan analysis. The calibration curve was rectilinear over the range 0.2 to 200 ng and the coefficient of variation (n = 8) for the injection of propafenone was 9.6%. Acebutolol, administered orally to subjects, was detected in urine together with its major metabolite diacetolol.
Drugs HPLC Mass spectrometry Heated reaction Interface pH

"Chemiluminescent Determination Of Tiopronin And Its Metabolite, 2-mercaptopropionic Acid, In Urine By HPLC Coupled With A Flow Injection Set-up"
Biomed. Chromatogr. 1997 Volume 11, Issue 2 Pages 115-116
Yining Zhao, Willy R. G. Baeyens, Xinrong Zhang, Kenichiro Nakashima, A. C. Calokerinos, Guido Van der Weken

Abstract: Based on a chemiluminescent approach for the detection of tiopronin applying a Ce(1V) oxidation system sensitized by quinine with flow injection analysis (FIA), described in an earlier paper (Zhao et al., 1996), a simple, selective and sensitive chemiluminescent-HPLC method for the measurement of tiopronin and 2-MPA in urine was developed. The chromatographic conditions were optimized to provide good resolution and short retention times; moreover the detection occurs easily as no derivatization reaction is required.
Tiopronin HPLC Chemiluminescence

"Flow Injection Analysis For Glucose With Chemically Modified Enzyme Membrane Electrode"
Bunseki Kagaku 1984 Volume 33, Issue 4 Pages 213-217
Yao, T.;Nakanishi, K.;Wasa, T.

Abstract: The electrode was constructed by cross-linking glucose oxidase with catalase (electrode A) or with peroxidase (electrode B) and immobilizing the enzymes on a platinum sheet treated with (3-aminopropyl)triethoxysilane. The method involved the enzymatically catalyzed oxidation of β-D-glucose, with amperometric detection of the dissolved O consumed (electrode A) or the Fe(CN)63- generated from Fe(CN)64- (electrode B); measurements were made (vs. a silver - AgCl reference electrode) at -0.7 V (electrode A) and 0.0 V (electrode B). Peak currents were rectilinearly related to glucose concentration. of 20 to 800 mg dl-1 for electrode A (5 µL injections) and of 30 to 400 mg dl-1 for electrode B (1 µL injections). The technique was applied to the determination of glucose in human serum and urine with satisfactory precision (coefficient of variation 2 to 4%). The electrodes retained most of their original activity after repetitive use for two months. Diagrams of the amperometric-detector arrangement and of the flow injection system are presented.
Glucose Amperometry Electrode Electrode Electrode Immobilized enzyme

"Fluorimetric Determination Of Kynurenine Derivatives By High Performance Liquid Chromatography With Hydrogen Peroxide And Sodium Carbonate"
Bunseki Kagaku 1984 Volume 33, Issue 7 Pages E315-E322
Iinuma, F.;Tabara, M.;Mawatari, K.;Suzuki, M.;Watanabe, M.

Abstract: Diluted and acidified human urine (24-h collection) was cleaned-up on a column of Dowex 50-X12 (H+ form) with 5 M HCl as eluent, and the eluate was adjusted to pH 2 to 3 with Na2CO3 and acetic acid. The solution was filtered, and the filtrate was submitted to HPLC on a column (25 cm x 4 mm) of LiChrosorb RP-18 (10 µm), with 50 mM acetate buffer (pH 4.1), 0.1 M in Na2SO4 and 10 µM in CuSO4, as mobile phase (1.5 mL min-1). Post-column derivatization was effected in a reaction coil with a Na2CO3 - CuSO4 - H2O2 reagent, and the products were detected by fluorimetry at 385 nm (excitation at 315 nm). Calibration graphs were rectilinear for 1 to 100 ng, 2 to 100 ng and 50 ng to 1 µg for kynurenine(I), N-formylkynurenine(II) and 3-hydroxykynurenine, respectively; the limit of determination for I and II was 25 ng mL-1. In the determination of 10 ng of I or II, the coefficient of variation were <3%.
Kynurenine HPLC Fluorescence Ion exchange Post-column derivatization

"Fluorimetric Determination Of 5-hydroxyindole Derivatives By High Performance Liquid Chromatography With Cobalt(II) Chloride, Sodium Carbonate And Sodium Hydroxide"
Bunseki Kagaku 1984 Volume 33, Issue 7 Pages E323-E330
Iinuma, F.;Mawatari, K.;Tabara, M.;Watanabe, M.

Abstract: Human urine, from a 24-h collection, was acidified with HClO4 and diluted, then cleaned-up on a column of Sephadex G-10, and the hydroxyindole derivatives were eluted with 0.05 M phosphate buffer (pH 7.7). The eluate was submitted to HPLC on a column (5 cm x 4 mm) of LiChrosorb RP-8 (5 µm), with 50 mM acetate buffer (pH 4.4), 0.1 M in Na2SO4 and 0.5 µM in CoCl2, as mobile phase (0.75 mL min-1). Post-column derivatization was effected in a reaction coil (at 180°C) with 0.5 M Na2CO3 - 2 M NaOH, and the fluorescence of the derivatives was measured at 460 nm (excitation at 360 nm). 5-Hydroxyindol-3-ylacetic acid down to pmol levels could be determined by this method. Hydroxyindole derivatives could also be determined in the eluate from the clean-up stage by a manual fluorimetric procedure based on use of the same reagents.
5-Hydroxyindole derivatives HPLC Fluorescence Heated reaction Post-column derivatization

"Determination Of Silicate By Flow Injection Analysis Coupled With A Suppression Column And Solventextraction System"
Bunseki Kagaku 1984 Volume 33, Issue 12 Pages E535-E538
Ogata, K.;Soma, S.;Koshiishi, I.;Tanabe, S.;Imanari, T.

Abstract: The sample (50 µL) is injected into a stream (0.5 mL min-1) of 0.2 M HCl and passes through a column (20 cm x 2 mm) of Dowex 1-X8 resin (molybdate form; 200 to 400 mesh) to remove phosphate. The stream then merges with a stream (0.5 mL min-1) of 2.14% (NH4)6Mo7O24.4H2O solution in 0.2 M HCl and, after passage through a reaction tube at 50°C, is segmented with isobutyl methyl ketone (0.5 mL min-1). After passage through an ice bath and phase separation, the absorbance of the organic stream is monitored at 400 nm. The response is rectilinear for up to 1 µg mL-1 of Si, the limit of detection is 0.01 µg mL-1, and the sampling rate is ~40 h-1. The mean recovery of Si added to human urine (diluted 100-fold with 0.2% HCl before analysis) was 98%.
Silicate Ion exchange Spectrophotometry Sample preparation Solvent extraction Heated reaction Reactor Organic phase detection

"Gel-chromatographic Deproteinization For Fluorimetric Catalytic Determination Of Iodide And Thiocyanate"
Bunseki Kagaku 1987 Volume 36, Issue 11 Pages 811-814
Tanaka, A.;Imasaka, Y.;Hayashi, K.;Deguchi, T.

Abstract: Sample solution containing 100 ppm of lysozyme, 0.2 µM-I- and 20 µM-SCN- was applied to a gel-filtration column (25 cm x 8 mm) of Sephadex LH-20 or G-20 with an eluent of 0.3 M NaCl at 1.3 mL min-1. Iodide and SCN- were determined in a flow injection analysis system by fluorimetry at 350 nm (excitation at 254 nm) via catalysis of the redox reaction between Ce(IV) and As(III). Calibration graphs were rectilinear from 0.03 to 4 µM-I- and 3 to 20 µM-SCN-. Components present in human urine did not interfere. The use of ion chromatography in conjunction with this technique is also described.
Iodide Thiocyanate ion SEC Fluorescence Catalysis Interferences

"Development Of A Capillary Stream Sensor For Potassium Using A Membrane Extraction Method With Coaxial Microporous Tube"
Bunseki Kagaku 1990 Volume 39, Issue 11 Pages 711-716
Korenaga, T.;Izawa, M.;Ito, T.;Takahashi, T.

Abstract: A sensor (illustrated), based on extraction of K into crown ethers, was developed and applied in (i) continuous - flow (diagram given) and (ii) flow injection analysis. Sample solution was injected into a carrier stream of 1 mM sodium picrate (0.1 mL min-1) contained in a microporous PTFE tube (2.0 mm o.d.; 0.9 mm i.d.; 0.8 µm pore size; 62% porosity) which was inside a second PTFE tube (2.4 mm i.d.) carrying the extraction solvent. The extraction solvent was 1,2-dichloroethane containing 10 mM 18-crown-6 (0.1 mL min-1) and the absorbance was continuously monitored at 370 nm in an 8 µL flow cell. Methods i and ii were applied in the determination of 10 to 120 µM-K+ in natural waters and 0.1 to 0.6 mM K+ in human urine, respectively. Results agreed well with literature values and recoveries were satisfactory.
Potassium Spectrophotometry Sample preparation Sensor Microporous membrane Crown ether Flowcell Extraction

"Direct Injection Method For Quantitation Of δ-aminolevulinic Acid In Urine By High Performance Liquid Chromatography"
Chem. Pharm. Bull. 1992 Volume 40, Issue 7 Pages 1948-1950
Kondo M, Kimura H, Maekubo T, Tomita T, Senda M, Urata G, Kajiwara M

Abstract: For the cited determination, urine was directly injected onto a JASCO AA-pak Li HPLC column (10 cm x 6 mm) packed with cation-exchange resin (5 µm). HPLC was performed at 65°C with 0.1 M Li citrate (pH 4.9) as mobile phase (0.6 mL min-1) and fluorimetric detection at 440 nm (excitation at 350 nm) after post-column derivatization with o-phthalaldehyde. Calibration was rectilinear up to 60 nmol (with peak areas measured) and the detection limit was 10 pmol. The coefficient of variation was 2.65% and the recovery was 103%. Good correlation with a colorimetric method was observed (r = 0.979). The method was applied to the measurement of I in healthy volunteers, patients with acute intermittent porphyria and workers occupationally exposed to lead.
δ-Aminolevulinic acid HPLC Fluorescence Post-column derivatization

"Chemiluminescence Determination Of Tiopronin And Its Metabolite 2-mercaptopropionic Acid In Human Urine By HPLC Coupled With Flow Injection"
Chromatographia 1997 Volume 44, Issue 1-2 Pages 31-36
Yining Zhao, W. R. G. Baeyens, X. R. Zhang, A. C. Calokerinos, K. Nakashima, G. Van Der Weken and A. Van Overbeke

Abstract: Urine collected following oral administration of tiopronin (I) was treated with 2 M TCA and centrifuged at 2000 rpm for 5 min. The supernatant was adjusted to pH 3 with NaOH and a portion (150 µL) was injected into a 5 µm LiChrospher RP-18 column (12.5 cm x 4 mm i.d.) equipped with a pre-column with aqueous 25 mM octanesulfonic acid sodium salt/50 mM acetate buffer as mobile phase (8 ml/min) and tetrabutylammonium bromide/cetrimonium bromide of pH 5.5-7 as ion-pairing agents, through PTFE tubing and coupled with FIA equipment (details given) and chemiluminescence detector. The optimization of operational parameters was investigated. Calibration graphs were linear from 1-200 µM-I and 4-400 µM-2-mercaptopropionic acid (II). Detection limits (n = 10) were 0.8 µM-I and 1 µM-II. The corresponding recoveries were from 96-104% and 104-109%. The method offers high selectivity and sensitivity, simple sample treatment and the use of unsophisticated instrumentation.
Tiopronin 2-Mercaptopropionic acid HPIC Chemiluminescence Post-column derivatization Sensitivity Selectivity Optimization

"Quantitation Of Tyrosine O-sulfate In Human Urine By Ion-pair Reverse-phase High Performance Liquid Chromatography"
Clin. Chim. Acta 1990 Volume 193, Issue 3 Pages 193-197
Masahito Suiko, P. H. Prasantha Fernando, Yoshio Arino, Masafumi Terada, Seiichiro Nakatsu and Ming-Cheh Liu,*

Abstract: Filtered urine was treated with Dowex 50W-X8 resin (c.f. Tallan et al., J. Biol. Chem., 1955, 217, 703). The supernatant solution was diluted 10-fold with water and 10 µL portions were analyzed by ion-pair HPLC on a column (25 cm x 4.6 mm) of Vydac C18 operated at 40°C, with 10% acetonitrile - 0.03 M KH2PO4 - 0.01 M tetrabutylammonium phosphate as mobile phase (1 mL min-1) and measurement of the absorbance at 261 nm or the fluorescence at 455 nm (excitation at 340 nm) following post-column derivatization with phthaldialdehyde (pH 10) in the presence of N-acetylcysteine. The calibration graph was rectilinear for 0.13 to 19 µg mL-1 of tyrosine-O-sulfate and down to 0.5 pmol could be determined. Recoveries were quantitative.
Tyrosine sulfate ester HPLC Fluorescence Clinical analysis Column Post-column derivatization

"Assessment Of The Automated Colorimetric And The High Performance Liquid Chromatographic Methods For Nicotine Intake By Urine Samples Of Smokers' Smoking Low- And Medium-yield Cigarettes"
Clin. Chim. Acta 1991 Volume 196, Issue 2-3 Pages 159-166
Sakari A. Kolonen* and Eino V. J. Puhakainen

Abstract: HPLC was essentially as described previously (Arch. Toxicol., Suppl., 1988, 12, 423), whilst the colorimetric barbituric acid (I) test with use of a continuous-flow analyzer. was as described by Puhakainen (Clin. Chim. Acta, 1987, 170, 255). HPLC determined only cotinine, and calibration graphs (treated urine samples) were rectilinear over the concentration. range 0.05 to 1.0 mg L-1 with coefficient of variation in the range 2.4 to 5.0%. The detection limit was 2 µg L-1 and the throughput was 50 per day. I could be used to detect most of the nicotine metabolites, and the calibration graph was rectilinear over the range 0 to 40 mg L-1 cotinine equivalents, with coefficient of variation in the range 2.2 to 4.2%. The subtraction of interference arising from the natural color of urine (cotinine equivalent of ~0.6 to 0.7 mg l-1) reduced the throughput of samples to 150 per day. It was concluded that use of I was an inexpensive and rapid alternative to HPLC for estimating the nicotine exposure of smokers.
Nicotine HPLC Clinical analysis Spectrophotometry Automation Interferences Low cost

"Improved Methods For Determination Of Fluoride In Biological Materials"
Fluoride 1986 Volume 19, Issue 1 Pages 22-25
K Seifert, B Dominok, GW Dominok

Abstract: Fluoride is separated from cartilage or aortic tissues without ashing by an adaptation of the method of Yoshida et al. (Anal. Abstr., 1979, 37, 6B109). The reaction takes place in a closed apparatus comprising a 100 mL flask in series with two gas bubblers, each containing 25 mL of 0.1 M NaOH. The sample, 50 mL of water and two drops of hexamethyldisiloxane are placed in the flask, and 40 mL of concentrated H2SO4 is added to the sample through a dropping funnel. The trimethylsilanol(I) produced reacts with the F- to form fluorotrimethylsilane(II), which is swept by N (50 mL min-1) to the bubblers. II is converted by the alkali back into I, which is extracted into toluene before measurement of the F- so liberated in 0.45 M HClO4 medium with an I--selective electrode. Urine is analyzed directly for F- in 0.5 M HClO4 medium containing 0.001% of Triton X-100 by using two F--selective electrodes in a flow injection system. The latter method was applied to urine of persons drinking fluoridated water or occupationally exposed to F. The former method was applied to tissues from adults and infants, and the results are reported.
Fluoride Electrode Electrode Sample preparation Surfactant Triton X

"Spectrophotometric Flow Injection Determination Of Thiocyanate"
Indian J. Chem. A 1997 Volume 36, Issue 4 Pages 344-346
ENSAFI A.A.

Abstract: The determination was performed using a previously described flow injection system (Ensafi, Ibid., 1997, 36, 105). The following optimum conditions were used: 0.4 M sodium azide; 0.175 mM iodine solution (prepared by dissolving I2 in KI solution); and a pH of 5. Sodium azide solution, phosphate buffer, iodine solution and water were pumped at a flow rate of 30 ml/h. A portion (300 µL) of thiocyanate solution was injected and the absorbance was read at 349 nm after reaction in a 300 cm mixing coil at 25°C. The calibration graph was linear from 0.005-1.8 µg/ml and the limit of detection was 0.62 ng/ml. The RSD (n = 10) was 1.3% and the sample throughput was ~40/h. The method was applied to the determination of thiocyanate in waste water and urine. An interference study is described.
Thiocyanate ion Spectrophotometry Detection limit Interferences Optimization

"Certification Of Cocaine And Benzoylecgonine In A Human Urine Standard Reference Material"
J. Anal. Toxicol. 1992 Volume 16, Issue 3 Pages 158-162
Ellerbe P, Tai SS, Christensen RG, Espinosa-Leniz R, Paule RC, Sander LC, Sniegoski LT, Welch MJ, White E 5th

Abstract: Cocaine (I) was determined Standard Reference Material 1508 (freeze-dried human urine) by GC - MS and HPLC methods and benzoylecgonine (II) was determined by GC - MS and FIA - thermospray MS (details given). Concentrations were determined for three levels of I and three levels of II. After one year, the concentration. of I and II were determined again by GC - MS in order to investigate the stability of the standard; results showed no indication of any decomposition having occured. The precision of the measurements show that material is suitable for use as a control material and as an accuracy benchmark for the drug testing community. The concentrations of cocaine and benzoylecgonine (BE) in Standard Reference Material (SRM) 1508, cocaine and metabolites in freeze-dried human urine, were determined at the National Institute of Standards and Technology (NIST, formerly NBS) by two independent methods. For cocaine, one method was based on gas chromatography/mass spectrometry (GC/MS); the other was based on high performance liquid chromatography (HPLC). For BE, one method was based on GC/MS; the other was based on flow injection analysis/thermospray mass spectrometry (FIA/MS). The results for each pair of methods were statistically evaluated. Concentrations were determined in the SRM for three levels of cocaine and three levels of benzoylecgonine. Methylecgonine, although present in the material, was not determined. For cocaine, the concentrations were 90, 263, and 429 ng/mL of human urine. For BE, the concentrations were 103, 259, and 510 ng/mL of human urine.
Cocaine Benzoylecgonine Mass spectrometry Reference material Method comparison

"Fast Screening For Drugs Of Abuse By Solid Phase Extraction Combined With Flow Injection Ionspray-tandem Mass Spectrometry"
J. Anal. Toxicol. 1998 Volume 22, Issue 4 Pages 319-328
W. Weinmann (Wolfgang) and M. Svoboda

Abstract: A fast anal. approach for the simultaneous quant. screening for illicit drugs in serum and urine without tedious chromatography separation steps was developed by combining solid phase extraction (SPE) followed by flow injection analysis (FIA) with ion spray-ionization and tandem mass spectrometry (MS-MS) detection using a PE Sciex API 300 triple-quadrupole MS. MS-MS anal. was performed by sequentially isolating the precursor ions of the analytes and their deuterated standards with subsequent fragmentation and monitoring of one fragment ion for each substance. A multiple-reaction monitoring experiment was set up for morphine (MO), codeine (COD), amphetamine (AMP), benzoylecgonine (BZE), and their deuterated analogs. For method evaluation, serum samples spiked with 2-1000 ng of each drug and deuterated standards were extd. by mixed-mode SPE, redissolved in MeCN-NH4OAc-buffer, and directly injected by flow injection into the ion spray source. The specificity of this new method was demonstrated by testing compounds with similar chemical structure for interferences from the analytes of interest (e.g., hydromorphone, morphine glucuronide, and 6-monoacetylmorphine with MO; dihydrocodeine and hydrocodone with COD; cocaine [COC] and ecgonine methylester with BZE; methamphetamine with AMP). The possibility of interferences of such compounds with the FIA-ion spray-MS-MS screening method is discussed. Spiked serum samples and serum and urine samples from drug addicts and victims of drug abuse were analyzed with FIA-MS-MS and, after derivatization, with gas chromatography-mass spectrometry (GC-MS). Comparable quant. results were obtained with both methods; no interferences with metabolites or other compounds were found. The FIA-ionspray-MS-MS method is a fast, quant., sensitive, and highly specific alternative method to drug-screening by immunoassays, high-performance liquid chromatography, and GC-MS. It can be used for the simultaneous detection of different drugs and metabolites such as opiates, COC, AMP derivatives, and many other drugs.
Drugs Morphine Codeine Amphetamine Benzoylecgonine Mass spectrometry Mass spectrometry Solid phase extraction Interferences Method comparison

"Determination And Speciation Of Arsenic In Human Urine By Ion-exchange Chromatography - Flow Injection Analysis With Hydride Generation - Atomic Absorption Spectroscopy"
J. AOAC Int. 1994 Volume 77, Issue 2 Pages 441-445
Jimenez De Blas, O.;Vicente Gonzalez, S.;Seisdedos Rodriguez, R.;Hernandez Mendez, J.

Abstract: For the determination of total As in urine, the organic matter was oxidized by a mineralization procedure (Minoia et al., Med. Lavoro, 1978, 69, 681) before determination by FIA - hydride-generation AAS using a standard-additions method. Separation of metabolic forms of As was performed by cation-exchange on a column (20 m x 1 cm i.d.) of AG50W-X80 (H+ form; 100-200 mesh) washed with 0.5 M HCl. The urine sample was acidified with concentrated HCl before elution by gravity (~3 ml/min). The method was based on that previously described by Tam et al. (cf. Bull. Environ. Contam. Toxicol., 1979, 21, 371) and the fractions collected were analyzed for As species by FIA - hydride-generation AAS. The instrument used was a Model AA-1475 (Varian Analytical Instruments, Sunnyvale, CA, USA) with an air-acetylene flame and an hollow cathode lamp at 9 mA; As was detected at 193.7 nm (full operating conditions are listed). The detection limits were 2 ppb for each As form and 3 ppb for total As after mineralization of wine. Recoveries were 93, 91 and 85% for 10 ppb of inorganic As, 20 ppb of monomethylarsonic acid and 40 ppb of dimethylarsinic acid, respectively. RSD (n = 10) were 3.2-4.6%. The method can be used for studying exposure to As.
Arsenic Spectrophotometry Speciation Standard additions calibration

"Measurement Of Free And Total Hydroxyproline By Automated Flow Injection Of Serum Or Urine Samples From Maintenance Hemodialysis Patients With Renal Osteodystrophy"
J. Clin. Lab. Anal. 1994 Volume 8, Issue 5 Pages 267-272
Uji Y, Karmen A, Okabe H, Hata K, Miura M, Ozaki K, Minamizaki M, Shibata T, Inayama S

Abstract: For the determination of total hydroxyproline, 100 µL of plasma or 1 mL of urine was mixed with 200 µL of 12 M HCl and autoclaved for 3 h at 120°C. The hydrolysate was neutralized with 1 mL of 12 M KOH and 1 mL of 1 M L-cysteine. A 100 µL portion was injected into a carrier stream in a FIA system of chloramine T in borate buffer and KCl adjusted to pH 8.7 with 1 M KOH. The mixture was heated at 120°C in a mixing coil (24 m x 1 mm i.d.) in an Al block. The reaction mixture was merged with a stream of Ehrlich's reagent (1:1), the resulting solution passed through a reaction coil (10 m x 1 mm i.d.) to a double beam photometer for detection at 560 nm. Free hydroxyproline was determined as above but omitting the hydrolysis step and filtering the serum. Calibration graphs were linear up to 1.22 mM with a detection limit of 3.8 µM. The within-run RSD was 2.34, 2.25 and 2.53% for 76, 38 and 19 µM, respectively. The recovery of 10^-50 µM of hydroxyproline in urine was 92-104%. Results agreed well with those obtained by HPLC.
Hydroxyproline Spectrophotometry HPLC Clinical analysis Dialysis

"Fluorescence Detection Of Mexiletine And Its P-hydroxylated And Hydroxymethylated Metabolites In Human Plasma And Urine By High Performance Liquid Chromatography Using Post-column Derivatization With O-phthalaldehyde"
J. Liq. Chromatogr. Relat. Technol. 1994 Volume 17, Issue 3 Pages 659-671
T. Tateishi; K. Harada; A. Ebihara

Abstract: The cited determination was conducted on a Wakosil ODS column (25 cm x 4.6 mm i.d.) with a guard column (1 cm x 4.6 mm i.d.) of the same material, gradient elution (1 ml/min) with 10 mM H3PO4/methanol/1.4 mM 1-octanesulfonic acid (details given) and post-column reaction with o-phthalaldehyde for fluorimetric detection at 445 nm (excitation at 345 nm). The limits of detection were 2 ng/ml for mexiletine and p-hydroxymexiletine and 5 ng/ml for hydroxymethylmexiletine and calibration graphs were linear for 0.01-1 µg/ml for the three analytes. Inter- and intra-assay RSD are tabulated. The method was used to determine mexiletine and the two metabolites in plasma and urine after extraction with ethyl ether; urine was subjected to enzymatic hydrolysis before extraction. 4-Methylmexiletine was used as internal standard.
Mexiletine p-Hydroxymexiletine 6-Hydroxymethylmexiletine Fluorescence HPLC Post-column derivatization

"Urinary Excretion Of NG-dimethylarginines In Multiple Sclerosis Patients: Preliminary Observations"
J. Neurol. Sci. 1995 Volume 129, Issue 2 Pages 186-191
Nenoo Rawala, Yong-Ju Leea, John N. Whitakerb, Jong Ok Parkc, Woon Ki Paika and Sangduk Kim*, a,*

Abstract: The concentrations of NG,N'G-dimethylarginine and NG,NG-dimethylarginine were determined in the urine samples from multiple sclerosis (MS) and control subjects, using a highly sensitive HPLC post-column o-phthaldialdehyde derivatization method. The presence of approximately equal amounts of both dimethylarginine isomers, of Arg concentration nearly half of Me2Arg, and of the undetectable amount of NG-monomethylarginine were the characteristic urinary excretion pattern in all human samples studied. The urinary excretion of Me2(asym)Arg and Me2(sym)Arg from MS (n = 9) and control (n = 7) were analyzed: the mean values from the samples were approximately 20% (for all MS) and 33% (for chronic-progressive MS) lower than those from the control for both dimethylarginine-derivatives when compared to the respective compounds. Although there were contrasting trends between controls and MS patients in the relationship of urinary NG-dimethylarginines and myelin basic protein like material (MBPLM), the correlations were not significant. Differences in the ratios of the concentrations of the two dimethyl derivatives, Me2(sym)Arg/Me2(asym)Arg, were not significantly different between MS and control groups. These findings warrant further investigation of possible links between urinary excretion of NG-dimethylarginine and MBPLM in MS. The possible significance of myelin metabolism in relation to urinary NG-dimethylarginines in MS is discussed.
HPLC Post-column derivatization

"Simultaneous Automated Continuous-flow Analysis Of Total Oestrogen And Creatinine In Pregnancy Urine"
Med. Lab. Sci. 1979 Volume 36, Issue 3 Pages 293-296
Phillips, Susan D.

Abstract: Modifications of the methods of M. Lever et al. (1973) for estrogen and A. L. Chasson et al. (1961) for creatinine (I) are described. Estrogen standards were prepared by diluting the stock solution with urine from males; I standards were diluted with water. The diluted samples for I determination were taken from the estrogen waste-line and further diluted with water containing Brij-35 (30%) before reacting with alkaline picrate. This dilution decreases the need for dialysis of the urine and also decreases interferences by other substance. Any urines showing +++ or greater for glucose and(or) ketones, as determined by the Keto-diastix, were treated with octan-2-ol and NaBH4 (in glucose presence) and by boiling (in ketones presence). The through time for this automated determination is 11 min for I and 18 min for estrogens. (SFS)
Estrone Creatinine Clinical analysis Interferences

"Detection And Determination Of Acetone Using Semiconductor Sensors"
Pharmazie 1989 Volume 44, Issue 10 Pages 698-702
Reichel, J.;Seyffarth, T.;Guth, U.;Mobius, H.H.;Guckeritz, D.

Abstract: Investigations to examine not only the factors of influence on evaluation of acetone by self-prepared semiconductor gas sensors, but also to prove analytical properties, were carried out using different tools. A sensor temperature of 600°C and a carrier gas flow-rate of 5 L/h were found to be suitable conditions for the measurement of flow injection apparatus. The determination of 1 µL samples of aqueous solutions containing 1-700 g of acetone/l yielded deviations of 4 to 33%. Using a head space method, the working temperature of 370°C led to a maximum sensor response, the detection limit ranged from 37.5 to 50 mg of acetone/L. After quantifying 5 µL sample solutions of 40-600 mg/L, results with an accuracy of 1 to 36% were obtained. The method showed the possibility of distinguishing concentrations of acetone below and above 40 mg/l according to physiological and pathological urinary values. The tests carried out on 100 human urine samples provide a good agreement with the Legal reference method for samples containing physiological or strong pathological amounts of ketone bodies, but not for those including traces and small amounts. False-positive results might be caused by a possible presence of ethanol in urine.
Acetone Sensor Apparatus Optimization

"Sequential Injection Spectrophotometric Determination Of Orthophosphate In Beverages, Wastewaters And Urine Samples By Electrogeneration Of Molybdenum Blue Using Tubular Flow-through Electrodes"
Anal. Chim. Acta 2004 Volume 510, Issue 1 Pages 61-68
Francisca Mas-Torres, Jos&eacute; Manuel Estela, Manuel Mir&oacute;, Andreu Cladera and V&iacute;ctor Cerd&agrave;

Abstract: A novel and automated sequential injection procedure is proposed for the spectrophotometric determination of orthophosphate without requiring unstable chemical reducing species used in the classical molybdenum blue method. The flowing methodology is based on the on-line generation of the detectable species by electrochemical reduction of the 12-molybdophosphoric acid complex using a stainless steel tubular flow-through working electrode. The established method is linear up to 20 mg/l P, with coefficients of variation (n=10) of 2.4 and 1.8% for 2.0 and 10 mg/l P, respectively. The versatility of the sequential injection method to analyze samples containing high orthophosphate levels has been demonstrated by the implementation of a dilution chamber as well as flow-reversal techniques, yielding relative standard deviations (n=17) better than 2.0% for standards containing 200 and 800 mg/l P. The proposed analyzer. features an extremely wide dynamic range (viz., 0.3-800 mg/l) as well as improved tolerance to silicate interference, so that Si/P ratios higher than 50 are tolerated at the 5% level. Electrochemical conditions, reagent concentrations and physical variables have been thoroughly investigated. The method has been applied to the determination of orthophosphate in wastewaters as well as beverages and biological samples containing high concentrations of the target analyte. The t-test comparison of the means for the developed sequential injection system with electroreduction and both the molybdenum blue classical spectrophotometric batch procedure and inductively coupled plasma-optical emission spectrometric detection selected as external reference methods revealed that there is no evidence of significant differences between the obtained results at the 95% confidence level.
Phosphate Spectrophotometry Sequential injection Method comparison Interferences Flow reversal Gradient technique Mixing chamber Electrochemical reagent generation

"A Multisyringe Flow Injection System With Immobilized Glucose Oxidase Based On Homogeneous Chemiluminescence Detection"
Anal. Chim. Acta 2004 Volume 508, Issue 1 Pages 23-30
Mat&iacute;as Manera, Manuel Mir&oacute;, Jos&eacute; Manuel Estela and V&iacute;ctor Cerd&agrave;

Abstract: In this paper, enzyme containing reactors are for the first time implemented in the multisyringe flow injection analysis (MSFIA) technique interfaced with chemiluminescence detection for biochemical assays. The automated methodology is based on the on-line substrate conversion in an oxidase packed-bed reactor and the post-column chemiluminogenic catalyzed-reaction of the generated oxidising species with an organic molecule (namely, 3-aminophthalhydrazide) in front of the photosensor module. Various catalysts in homogeneous phase are compared taking advantage of the benefits of the MSFIA concept. On one hand, mineral catalysts (namely, Co(II)) are assessed, on the other hand, minute and accurate volumes of soluble organic species (viz., horseradish peroxidase (HRP)) are readily handled without requiring further immobilization protocols. The potentials of the MSFIA-CL concept with immobilization of the proper oxidase protein are demonstrated using glucose as a model of substrate. Despite the different pH and kinetic requirements for both the substrate conversion in the enzyme-reactor and the Co(II)/HRP-mediated luminol oxidation integrated in the flow system, the MSFIA approach warrants maximum yields owing to the independent optimization of the physical and chemical parameters of the various reactions involved. Under the optimized configurations and experimental variables, dynamic working ranges from 2.5 x 10^-6 to 1.0 x 10^-3 mol L-1 glucose may be obtained for both detection schemes by proper photomultiplier gain selection. The detection and determination limits calculated at the 3s and 10s level were 8.6 x 10^-7 and 2.0 x 10^-6 mol L-1 glucose, respectively, for the Co(II)-luminol system, and 1.3 x 10^-6 and 2.3 x 10^-6 mol L-1 glucose, respectively, for the HRP-luminol procedure. The repeatability (n=10) at the 1.0 x 10^-5 mol L-1 level was slightly better for the Co(II)-catalyzed reaction (2.5% versus 4.0%). The developed MSFIA-CL methodology was used for kinetic studies of the mutarotation reaction between α and β anomeric forms of glucose, obtaining quantitative information of the specific glucose oxidase (GOD) anomer formed at prefixed intervals of time. It was also successfully applied to the determination of traces of glucose in complex matrices, namely, human urine, soft drinks and fruit juices, exploiting the Co(II)-mediated luminol oxidation.
Glucose Chemiluminescence Multisyringe Interferences Immobilized enzyme Optimization Column

"Simultaneous Determination Of Water-Soluble Vitamins In Human Urine By Fluorescence In A Flow-Injection Analysis"
J. Liq. Chromatogr. Relat. Technol. 2006 Volume 29, Issue 3 Pages 329-338
Lai-Hao Wang, Heng-Chieh Hung

Abstract: Fluorescence in flow-injection analysis is described for the simultaneous determination of thiamine, riboflavin, and folic acid. Its detection limit linearity and reproducibility were examined. The kinetic method is based on the enhancing effect of thiamine and riboflavin on the fluorescence generated by oxidizing to thiochrome with alkaline ferricyanide. Different parameters affecting this reaction were thoroughly studied. The procedure was applied to the determination of thiamine and riboflavin and folic acid in human urine samples.
Thiamine Riboflavine Folic acid Fluorescence Kinetic

"A Study On The Micelle-sensitized Ce(IV)-Na2S2O3-norfloxacin Chemiluminescence System And Its Applications"
Luminescence 2005 Volume 20, Issue 3 Pages 220-225
Zenghong Xie, Sulan Liao, Guonan Chen*

Abstract: A new chemiluminescence (CL) flow-injection method was developed for the determination of norfloxacin. The method is based on the CL reaction of norfloxacin with sodium thiosulphate and Ce(IV) in sulphuric acid medium sensitized by sodium dodecylsulphate. Under optimum conditions, the CL intensity is proportional to the concentration of the norfloxacin in the range 3.89 x 10^-8-7.18 x 10^-6 g/mL. The detection limit (3 s[sol ]k) was 2.21 x 10^-9 g[sol ]mL for norfloxacin. The method has been applied successfully to the determination of norfloxacin in pharmaceutical formulations and human urine. The mechanism for this chemiluminescence system is discussed.
Norfloxacin Chemiluminescence Optimization Micelle

"A Sensitive Chemiluminescence Flow Injection Procedure For Assay Of Fluoride In Waters And Humane Urine By Use Of Immobilized Reagents#"
Spectrosc. Lett. 2003 Volume 36, Issue 1-2 Pages 117-131
Zhenghua Song and Ni Zhang

Abstract: A new simple, rapid, selective and sensitive analytical procedure based on chemiluminescence (CL) detection is described for the determination of free fluoride at sub-nanogram levels by use of controlled-reagent-release technology in a flow injection system. The analytical reagents involved in the CL reaction, including luminol and periodate, were both immobilized on anion-exchange resins in a flow injection system. Through water injection luminol and periodate were eluted from the anion exchange column to generate the chemiluminescence, which was enhanced in the presence of fluoride. The increased CL intensity was linear with fluoride concentration in the range from 0.1 to 10 ng mL-1. The limit of detection was 20 pg mL-1 (3s) and the relative standard deviation (RSD) was 1.02% (n = 5) for a 1.0 ng mL-1 fluoride. At a flow rate of 2.0 mL min-1, including sampling and washing, a typical analytical procedure could be performed in 0.5 min with a RSD of less than 3.0%. The proposed method was successfully applied to determine the free fluoride in water and human urine, and the results were in good agreement with those obtained by ion chromatography.
Fluoride Chemiluminescence Method comparison Immobilized reagent

"Multisyringe Flow Injection Analysis Of Stable And Radioactive Yttrium In Water And Biological Samples"
Anal. Chim. Acta 2005 Volume 539, Issue 1-2 Pages 189-194
Y. Fajardo, E. G&oacute;mez, F. Garcias, V. Cerd&agrave; and M. Casas

Abstract: A novel multisyringe flow injection (MSFIA) method for the determination of stable and radioactive yttrium by means of a liquid-liquid extraction has been developed. An on-line column containing di-2-ethylhexylphosphoric acid (HDEHP) - a highly selective extractant for the analyte - adsorbed on a C18 support is employed to carry out the isolation from the matrix. Stable and radioactive yttrium concentrations are determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and by a low background proportional counter, respectively. The proposed method shows important advantages because the manual handling of radioactive samples is avoided and throughput is increased. Moreover, as the extractant can be reused, cost per analysis and waste generation are reduced. The lower limit of detection (LLD) of stable yttrium is 10 µg l-;1, whereas for 90Y is 0.05 Bq. The automated isolation process yields a yttrium recovery close to 100% with a relative standard deviation of 2.3% (n = 10). Our methodology has been successfully applied to different spiked water and biological samples.
Yttrium Spectrophotometry Scintillation counter Radiochemical Speciation Multisyringe Extraction C18 Column