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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Plant

Classification: Plant -> tea

Citations 15

"Flow Injection Analysis For Traces Of Zinc With Immobilized Carbonic Anhydrase"
Anal. Chim. Acta 1985 Volume 178, Issue 2 Pages 209-215
Kunio Kashiwabara, Toshiyuki Hobo, Eigo Kobayashi and Shigetaka Suzuki

Abstract: Bovine carbonate dehydratase was immobilized on CNBr-activated Sepharose 4B and packed in a small glass column. The metal ions were removed from the enzymes easily by passing 0.01 M pyridine-2,6-dicarboxylic acid through the column at 1.0 mL min-1. The activity increase after passing a Zn sample solution through the column was measured by injecting 0.1 M 4-nitrophenyl acetate in dimethyl sulfoxide into the Tris buffer stream and measuring at 400 nm the 4-nitrophenol formed. The increase in peak area was proportional to the amount of Zn in the sample. A rectilinear calibration graph was obtained for 10 to 400 ng of Zn. The coefficient of variation for 0.13 µg of Zn was 4.9%. The method was successfully applied to the determination of Zn in tea, sediment and spring water. The immobilized enzyme can be used repeatedly and Zn can be concentrated on the column, permitting very low concentration. to be determined.
Zinc Spectrophotometry Immobilized enzyme Preconcentration

"Fluoride Ion-selective Electrode In Flow Injection Analysis. 3. Applications"
Anal. Chim. Acta 1986 Volume 188, Issue 1 Pages 151-164
Wolfgang Frenzel and Peter Brätter

Abstract: Optimum conditions are described for the determination of trace amounts of F- in tap water, beverages and urine by flow injection potentiometry with a F--selective electrode. Good sensitivity (1 µg l-1) and long-term stability were obtained, with a sample throughput of 30 to 40 h-1, based on triplicate injections at 120 h-1. Total ionic strength adjustment buffer (TISAB-III) was unsuitable for the analysis of undiluted tea and urine. Such samples with high inherent I and large amounts of interfering elements required a modified citrate-containing TISAB buffer. Recoveries of 0.01 to 1 mg L-1 of F- added to tap water, tea and urine were 91 to 106%. The apparatus allowed rapid changes between buffers and carrier streams.
Fluoride Electrode Potentiometry Interferences

"Simultaneous Spectrofluorimetric Determination Of Selenium(IV) And (VI) By Flow Injection Analysis"
Analyst 1997 Volume 122, Issue 3 Pages 221-226
M. J. Ahmed, C. D. Stalikas, P. G. Veltsistas, S. M. Tzouwara-Karayanni and M. I. Karayannis

Abstract: A sample (100 µL) was injected into a carrier stream of 2 M H2SO4 at a flow rate of 0.1 ml/min and mixed with a reagent stream of 0.2 mM 2-(α-pyridyl)thioquinaldinamide in propan-2-ol at a flow rate of 0.3 ml/min. The fluorescence intensity due to Se(IV) was measured at 500 nm (excitation at 350 nm). A second portion (100 µL) was then injected into the carrier stream and passed through a coil (40 cm x 0.8 mm i.d.) where it was irradiated at 254 nm. The irradiated sample stream was then mixed with the reagent stream and the fluorescence intensity due to total Se was measured. Se(VI) was determined from the difference in the two fluorescence intensity values. The calibration graphs were linear from 0.01-2.2 and 0.1-2.4 µg/ml Se(IV) and Se(VI), respectively; corresponding detection limits were 1 and 10 ng/ml. RSD were 0.1-2% (n=5). The throughput was 25 samples/h. The method was applied to the analysis of alloys, hair, tap and lake water, sediments, soil, tea, flour and eggs. A simple, sensitive, highly selective, automatic spectrofluorimetric method for the simultaneous determination of selenium (IV) and (VI) as selenite-selenate by flow injection analysis (FIA) has been developed. The method is based on the selective oxidation of the non-fluorescent reagent 2-(α-pyridyl)thioquinaldinamide (PTQA) in acidic solution (1.5-3.0 M H2SO4) by Se(IV) to give an intensely fluorescent oxidation product (lambda ex =350 nm; lambda em = 500 nm). Selenium (VI) is reduced online to Se(IV), in a reduction coil installed in a photo- reactor, which is then treated with PTQA and the fluorescene due to the sum of Se(IV) and Se(VI) is measured; Se(Vi) is determined from the difference in fluorescence values. Various analytical parameters, such as effect of acidity, flow rate, sample size, dispersion coefficient, temperature, reagent concentration and interfering species were studied. The photo-reduction conditions were optimized, with an FIA procedure, for Se(VI) on the basis of its reduction efficiency. The calibration graphs were rectilinear for 0.1-2.4 µg mL-1 of Se(VI) and 10 ng mL-1 - 2.2 µg mL-1 of Se(IV), respectively. The method was applied to the determination of Se in several Standard Reference Materials (alloy, sediments and tea), as well as in some environmental waters (tap and surface water), food samples (flour and egg), a biological sample (human hair), soil sample and in synthetic mixtures. Up to 25 samples per hour can be analyzed with an RSD approximately 0.1-2%.
Selenium(IV) Selenium(VI) Fluorescence Speciation Photochemistry Selectivity Reference material Interferences

"Generation Of Volatile Cadmium Species With Sodium Tetrahydroborate From Organized Media: Application To Cadmium Determination By Inductively Coupled Plasma Atomic-emission Spectrometry"
J. Anal. At. Spectrom. 1993 Volume 8, Issue 6 Pages 847-852
M. C. Valdés-Hevia y Temprano, M. R. Fernández de la Campa and Alfredo Sanz-Medel

Abstract: For the continuous-flow determination of Cd by hydride-generation ICP-AES, generation was with 4% NaBH4 in 0.1% NaOH as reagent (0.75 ml/min) in a micellar medium of 0.01 mM didodecyldimethylammonium bromide in 0.4 M HCl (0.75 ml/min) to aid separation. A r.f. plasma with forward power of 900 W and detection at 214.44 nm was used. Calibration graphs were rectilinear for 1 µg/ml of Cd with a detection limit of 1 ng/ml and RSD of 2.1% at 50 ng/ml of Cd. The method was applied to the determination of Cd in tea infusions containing 5.8-22 ng/ml of Cd.
Cadmium Sample preparation Spectrophotometry Volatile generation Micelle PPB Volatile generation

"Post-chromatographic Derivatization And Detection Techniques For The Characterization Of Element Binding Types In Coffee And Tea"
Fresenius J. Anal. Chem. 1983 Volume 316, Issue 6 Pages 594-599
G. Weber und G. Schwedt

Abstract: Organic complexes of Cu, Zn and Fe present in coffee and tea were extracted into ethyl acetate and then determined by reversed-phase HPLC Both u.v. and conductivity detectors were used, and continuous-flow systems were developed for chemical derivatization of, e.g., phenols, amines, thiols, aromatic amines and carbonyl compounds. Zinc and Fe were determined by AAS (air - acetylene flame), and Cu was determined by flameless AAS Phenolic compounds, particularly flavonoids, were shown to be important as binding agents for the metals in tea.
Copper Iron Zinc HPLC Conductometry Spectrophotometry Complexation

"Hyphenated Techniques Combined With Atomic Spectrometry For Environmental Studies"
Microchem. J. 1995 Volume 51, Issue 1-2 Pages 88-98
Wang X. O., Zhuang Z. X., Yang P. Y. and Huang B. L.

Abstract: The development and application of hyphenated techniques combined with atomic spectrometries for environmental analysis at Xiamen University, China, are described. The techniques include: flow injection online microcolumns combined with AAS, GFAAS, ICP AFS and ICP-AES for trace and ultratrace analysis of water; flow injection online solvent extraction combined with AAS and ICP-AES; flow injection online hydride generation for the elemental analysis of Chinese herbs and rain by AAS and ICP-AES; flow injection online coprecipitation-dissolution for the determination of trace heavy metals in seawater and rain by GFAAS and ICP-AES; and HPLC combined with ICP-AES for multielement speciation analysis of Chinese tea.
Metals, trace Metals, heavy HPLC Fluorescence Spectrophotometry Spectrophotometry Spectrophotometry Spectrophotometry Spectrophotometry Sample preparation Review Coprecipitation Solvent extraction Volatile generation Speciation Ultratrace Volatile generation

"Enzymic Flow Injection Determination Of γ-aminobutyric Acid"
Anal. Lett. 1995 Volume 28, Issue 2 Pages 259-266
Horie, H.;Rechnitz, G.A.

Abstract: Samples (20 µL) were mixed with 20 µL 2.5 µM-NADP/10 µM-2-oxoglutarate and injected into a carrier stream (0.1 or 0.8 ml/min) of 50 mM Tris hydrochloride buffer of pH 8 containing 1 mM 2-mercaptoethanol and 200 mM Na2SO4 which passed to an enzyme reactor. The reactor comprised a column (3.5 cm x 3 mm i.d.) packed with 200 mg glutaraldehyde-treated glass beads that had been mixed with 80 mg/ml GABAse (4-aminobutyrate:2-oxoglutarate aminotransferase and succinic semialdehyde:NADP+ oxidoreductase) in 0.2 mL 50 mM sodium phosphate buffer of pH 7 overnight, then washed with phosphate buffer. The NADPH produced was determined fluorimetrically at 460 nm (excitation at 360 nm). The calibration graphs were linear from 1-500 and 0.5-500 µM-γ-aminobutyric acid (GABA) at 0.8 and 0.1 ml/min, respectively. No RSD are given. At 0.8 ml/min samples could be injected every minute. The enzyme reactor retained >60% activity over 10 days. Recoveries of GABA from spiked green tea infusions were 97-104% at a flow rate of 0.1 ml/min.
4-aminobutyric acid Fluorescence Glass beads Immobilized enzyme Column

"The Use Of Surfactants To Obtain Cadmium Atoms At Room Temperature And Its Application For The Cold Vapor AAS Determination Of The Metal"
Anal. Proc. 1995 Volume 32, Issue 2 Pages 49-52
A. Sanz-Medel, M. C. Valdés-Hevia y Temprano, N. Bordel García and M. R. Fernández de la Campa

Abstract: So far, mercury is the only metal that has been proved to be able to form a monoatomic vapor at room temperature. This property has been widely used in analytical techniques, particularly in atomic spectroscopy, where cold vapor atomic absorption spectrometry (CV-AAS) has become the most common method for the determination of low levels of Hg.In this communication we will show evidence that cadmium appears also to be able to form cold atomic vapor in appropriate conditions. Experimental results show that by reduction of Cd2+ with sodium tetrahydroborate in vesicles of didodecyldimethylammonium bromide (DDAB), some volatile cadmium species (probably hydrides) can be produced that transport the metal to the atomic absorption measurement cell, where atomic cadmium vapor has been proved to be present in measurable concentrations.Based on these facts, a new determination of traces of cadmium by cold vapor atomic absorption spectrometry is proposed. Such CV-AAS determination of the metal is very sensitive in normal conditions (detection limit of 0.08 ng ml-1) and the sensitivity can be improved further by working at lower temperatures for generation of the volatile species.
Cadmium Spectrophotometry Volatile generation Volatile generation

"Laccase-based Biosensor For Determination Of Polyphenols: Determination Of Catechols In Tea"
Biosens. Bioelectron. 1992 Volume 7, Issue 2 Pages 127-131
A. L. Ghindilis, V. P. Gavrilova and A. I. Yaropolov

Abstract: A new method of amperometric determination of phenolic compounds using an enzyme electrode is proposed. The latter represents the combination of the oxygen electrode and immobilized laccase. Analytical systems of flow injection and batch types were considered. A method of immobilization was developed that provided an increase in the stability of the enzyme. Optimal conditions for biosensor operation were found. The time needed for analysis in the flow injection mode was below 100 s. A column with immobilized enzyme could be used for up to 500 determinations of phenolic compounds without decrease of the enzyme activity. The practical validity of the method was demonstrated by tannin analysis in tea of different brands.
Catechols Amperometry Sensor Electrode Immobilized enzyme Optimization

"Rapid Determination Of Trace Zinc In Tea By Flow Injection Micelle-modified Spectrophotometry"
Fenxi Huaxue 1990 Volume 18, Issue 4 Pages 362-365
Qi, W.;Chen, X.G.

Abstract: The flow injection analysis equipment is described in detail. It was used to determine trace Zn in the Zn - 1-(2-pyridylazo)-2-naphthol (I) - Triton X-100 system. The carrier stream was NH3 - NH4Cl buffer solution (pH 8.8) at 3 mL min-1, and this was mixed with the reagent stream of ethanolic 0.05% I - 10% Triton X-100 (50 ml) at 1.25 mL min-1. The masking agents, sodium hexametaphosphate, sodium citrate and ammonium aminoisopropionate were used to avoid interference by Mn(II), Cu(II) and Co(II). Flow injection analysis can be used to determine Zn in tea, which contains high concentration. of Mg and Mn, without pre-separation. The sampling rate is 180 h-1, and the coefficient of variation was 1.6%.
Zinc Spectrophotometry Triton X Buffer pH Interferences Micelle Surfactant

"Simultaneous Determination Of Aluminum And Iron By Flow Injection Stopped-flow Spectrophotometry"
Fenxi Huaxue 1997 Volume 25, Issue 1 Pages 37-40
Zhang, A.M.;Wang, S.H.;Wang, H.S.;Cui, H.

Abstract: Sample was injected into the FIA system over 8 s and flowed at 2.5 ml/min into a carrier stream of 10 mL 0.2 M potassium hydrogen phthalate buffer of pH 5 to merge with a reagent stream containing aqueous 0.036% cetylpyridinium bromide at 2 ml/min. The mixture then flowed through a reaction coil (30 cm long) where it was reacted with 120 µL 0.008% Chrome Azurol S in a reactor (40 cm long). After stopping the flow for 20 s, the absorbance was measured at 620 nm. Al and Fe concentrations were calculated from linear calibration graphs ranging from 0-0.4 and 0-0.8 mg/l, respectively. Only Ni(II) and fluoride interfered. The method was applied to the simultaneous determination of Al(III) and Fe(III) in tap water, tea leaves and flour, with recoveries of 93.1-109% and RSD of 1-3.1%. The sampling frequency was 90 runs/h.
Iron Aluminum Spectrophotometry Stopped-flow Simultaneous analysis Interferences

"New Flow Injection Spectrophotometric Method For The Determination Of Tannins In Tea And Beer Using Iron(III) And 1,10-phenanthroline"
Food Chem. 1993 Volume 47, Issue 2 Pages 201-204
Consuelo Tomàs, Mercedes Celeste, Andreu Cladera, Enrique Gómez, JoséManuel Estela and Víctor Cerdà

Abstract: Tea was extracted for 1 h with boiling water and a portion (105 µL) of the filtered extract or degassed beer was injected into a stream of 0.4 M iron(III) chloride hexahydrate which was then merged with a stream of 0.5 M acetic acid of pH 3.5, followed by a stream of 15 mM 1,10-phenanthroline. All flow rates were 0.7 ml/min. The reaction mixture was passed through a mixing loop (0.5 m) and the difference in absorbances at 510 nm and 680 nm was recorded. Calibration graphs were linear for 2 mg/l of gallic acid. Recoveries were >88%. Sulfur dioxide and ascorbic acid interfered.
Tannins Gallic acid Sample preparation Spectrophotometry Interferences

"Application Of Flow Injection Analysis With Air-bubble Sandwich. 1. Determination Of Total Amount Of α-amino-acids In Tea"
Gaodeng Xuexiao Huaxue Xuebao 1990 Volume 11, Issue 8 Pages 822-824
Xu, Y.Y.;Sun, X.P.;Wu, Q.;Tian, L.C.

Abstract: α-Amino-acids were determined in tea samples sandwiched between two air bubbles by flow injection analysis with hydrated ninhydrin solution as color reagent. N2H4SO4 was used as reductant instead of SnCl2 to decrease the reaction time (to 5 min at 90°C) and to increase sensitivity. A small amount of Triton X-100 was used to prevent deposition and thus improve reproducibility and baseline stability. The detection limit was 5 mg l-1. Recovery was 97 to 106% with analysis of 80 samples/h. The average coefficient of variation was 2.8%.
Amino acids, α Spectrophotometry Sensitivity Triton X Surfactant Air segmentation

"Simultaneous Determination Of Iron, Copper And Cobalt In Food Samples By CCD-diode Array Detection-flow Injection Analysis With Partial Least Squares Calibration Model"
J. Phys: Conf. Ser. 2006 Volume 28, Issue 1 Pages 66-69
Jianping Mi, Yuanqian Li*, Xiaoli Zhou, Bo Zheng and Ying Zhou

Abstract: A flow injection-CCD diode array detection spectrophotometry with partial least squares (PLS) program for simultaneous determination of iron, copper and cobalt in food samples has been established. The method was based on the chromogenic reaction of the three metal ions and 2- (5-Bromo-2-pyridylazo)-5-diethylaminophenol, 5-Br-PADAP in acetic acid - sodium acetate buffer solution (pH5) with Triton X-100 and ascorbic acid. The overlapped spectra of the colored complexes were collected by charge-coupled device (CCD) - diode array detector and the multi-wavelength absorbance data was processed using partial least squares (PLS) algorithm. Optimum reaction conditions and parameters of flow injection analysis were investigated. The samples of tea, sesame, laver, millet, cornmeal, mung bean and soybean powder were determined by the proposed method. The average recoveries of spiked samples were 91.80%~100.9% for Iron, 92.50%~108.0% for Copper, 93.00%~110.5% for Cobalt, respectively with relative standard deviation (R.S.D) of 1.1%~12.1%. The sampling rate is 45 samples h-1. The determination results of the food samples were in good agreement between the proposed method and ICP-AES.
Clonidine Cobalt Copper Spectrophotometry Partial least squares Triton X Method comparison Optimization

"Flow-Injection Turbidimetric Determination Of Tannins In Tea Samples Using Copper(II)/Acetate As Precipitant Reagent"
Anal. Lett. 2005 Volume 38, Issue 3 Pages 511-522
Evandro Piccin, Heberth Juliano Vieira, Orlando Fatibello-Filho

Abstract: A flow-injection (FI) turbidimetric method for determination of tannins content in tea samples based on the precipitation reaction with copper(II) in acetate medium is proposed. In this method, 350 µL of 0.05 mol L-1 copper(II) and 350 µL of sample were injected simultaneously in two water carrier streams of a merging zones system. After mixing at a 50 cm coiled reactor, the mixture converged with a flow stream of 0.10 mol L-1 ammonium acetate solution producing a precipitate in a 100 cm coiled reactor that was monitored at 500 nm. Under the optimized experimental conditions, the calibration graph for tannic acid was linear in the concentration range from 18.0 to 725 mg L-1 with a detection limit of 6.49 mg L-1. The relative standard deviations (RSD) were smaller than 1.2% (n=10) for solutions containing 110 and 365 mg L-1 of tannic acid, and the analytical frequency was 90 determinations per hour. The results obtained in the analysis of tea samples (green, black, and brown) were compared with those provided by the Folin-Ciocalteu method.
Tannins Turbidimetry Method comparison Precipitation Optimization Merging zones