University of North Florida
Browse the Citations
-OR-

Contact Info

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

View Stuart Chalk's profile on LinkedIn

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

  • Publisher: Elsevier
  • FAD Code: SCAA
  • CODEN: SAMCAS
  • ISSN: 1386-1425
  • Abbreviation: Spectrochim. Acta A
  • DOI Prefix: 10.1016/j.saa,10.1016/S1386-1425
  • Language: English
  • Comments: Fulltext from 1939 V1

Citations 21

"A Simple And Rapid Flow Injection Chemiluminescence Determination Of Cysteine With Ru(phen)32+-Ce(IV) System"
Spectrochim. Acta A 2007 Volume 66, Issue 2 Pages 359-363
Yan Xiong, Houjiang Zhou, Zhujun Zhang, Deyong He and Chao He

Abstract: A new chemiluminescence system was developed for the determination of cysteine by flow injection system. This method is based on the reaction of L-cysteine with Ru(phen)32+ and Ce(IV) to produce chemiluminescence. The calibration curve was linear over the range 8.0 x 10^-7 to 4.0 x 10^-5 and 4.0 x 10^-5 to 1.0 x 10^-3 M with a detection limit of 7.0 x 10^-7 M (S/N = 3). The relative standard deviation of 4.0 x 10^-6 M cysteine was found 3.5% (n = 10). The influence of potential interfering substances was studied. The proposed method was successfully applied for the flow injection determination of cysteine in the real samples with minimum sampling rate of 90 sample/h. © 2006 Elsevier B.V. All rights reserved.

"Flow-injection Chemiluminescence Sensor For Determination Of Isoniazid In Urine Sample Based On Molecularly Imprinted Polymer"
Spectrochim. Acta A 2007 Volume 66, Issue 2 Pages 341-346
Yan Xiong, Houjiang Zhou, Zhujun Zhang, Deyong He and Chao He

Abstract: In this paper, molecularly imprinted polymer (MIP) of isoniazid is synthesized through thermal radical copolymerization of metharylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) in the presence of isoniazid template molecules. A novel flow injection chemiluminescence sensor for isoniazid determination is developed by packing the isoniazid-MIP into the flow cell as recognition elements. Isoniazid could be selectively adsorbed by the MIPs and the adsorbed isoniazid was sensed by its great enhancing effect on the weak CL reaction between luminol and periodate which were mixed in the flow cell. The enhanced CL intensity is linear in the range 2 x 10^-9 to 2 x 10^-7 g/mL and the detection limit is 7 x 10^-10 g/mL (3?) isoniazid with a relative standard deviation 2.8% (n = 9) for 8 x 10^-8 g/mL. The sensor is reversible and reusable. It has a great improvement in sensitivity and selectivity for CL analysis. As a result, the sensor has been successfully applied to determination of isoniazid in human urine. At the same time, the binding characteristic of the polymer to isoniazid was evaluated by batch method and the dynamic method, respectively. © 2006 Elsevier B.V. All rights reserved.

"Flow Injection-chemiluminescence Determination Of Phenol Using Potassium Permanganate And Formaldehyde System"
Spectrochim. Acta A 2007 Volume 66, Issue 1 Pages 58-62
Wei Cao, Xuemin Mu, Jinghe Yang, Wenbo Shi and Yongcun Zheng

Abstract: It is found that phenol can react with potassium permanganate in the acidic medium and produce chemiluminescence, which is greatly enhanced by formaldehyde. The optimum conditions for this chemiluminescent reaction are in detail studied using a flow injection system. The experiments indicate that under optimum conditions, the chemiluminescence intensity is linearly related to the concentration of phenol in the range 5.0 x 10^-9 to 1.0 x 10^-6 g mL-1 with a detection limit (3?) of 3 x 10^-9 g mL-1. The relative standard deviation is 1.2% for 4.0 x 10^-7 g mL-1 phenol solution in 11 repeated measurements. This method has the advantages of simple operation, fast response and high sensitivity. The method is successfully applied to the determination of phenol in the waste water. © 2006 Elsevier B.V. All rights reserved.

"Near-ultraviolet Chemiluminescence From The Reaction Of Ammonia With Hypobromite In Aqueous Solution"
Spectrochim. Acta A 2006 Volume 65, Issue 3-4 Pages 708-710
Paul S. Francis, Jacqui L. Adcock and Neil W. Barnett

Abstract: The chemiluminescence arising from the oxidation of ammonium chloride by sodium hypobromite in aqueous alkaline solution includes a series of peaks in the near-ultraviolet, which is not commonly observed in liquid-phase chemiluminescence. The dominant peak in that region has an intensity maximum at 292 nm and smaller peaks are observed at 313, 334 and 356 nm. The emitted photons are of similar energy to the Vergard-Kaplan transition of molecular nitrogen, a major product of this reaction. However, the spectral distribution is different to that of previously reported gas-phase chemiluminescence attributed to the Vergard-Kaplan transition.

"Chemometrics-assisted Simultaneous Determination Of Cobalt(II) And Chromium(III) With Flow-injection Chemiluminescence Method"
Spectrochim. Acta A 2006 Volume 65, Issue 1 Pages 67-72
Baoxin Li, Dongmei Wang, Jiagen Lv and Zhujun Zhang

Abstract: In this paper, a flow-injection chemiluminescence (CL) system is proposed for simultaneous determination of Co(II) and Cr(III) with partial least squares calibration. This method is based on the fact that both Co(II) and Cr(III) catalyze the luminol-H2O2 CL reaction, and that their catalytic activities are significantly different on the same reaction condition. The CL intensity of Co(II) and Cr(III) was measured and recorded at different pH of reaction medium, and the obtained data were processed by the chemometric approach of partial least squares. The experimental calibration set was composed with nine sample solutions using orthogonal calibration design for two component mixtures. The calibration curve was linear over the concentration range of 2 x 10^-7 to 8 x 10^-10 and 2 x 10^-6 to 4 x 10^-9 g/ml for Co(II) and Cr(III), respectively. The proposed method offers the potential advantages of high sensitivity, simplicity and rapidity for Co(II) and Cr(III) determination, and was successfully applied to the simultaneous determination of both analytes in real water sample. © 2005 Elsevier B.V. All rights reserved.

"A New Chemiluminescence Method For The Determination Of Nickel Ion"
Spectrochim. Acta A 2006 Volume 64, Issue 2 Pages 391-396
Li Na Li, Nian Bing Li and Hong Qun Luo

Abstract: A new chemiluminescence (CL) phenomenon described as the second-chemiluminescence (SCL) was observed and a strong CL signal was detected, when Ni(II) ion was injected into the mixture after the end of the reaction of potassium permanganate with alkaline luminol. The possible CL mechanism is proposed based on the kinetic curve of the CL reaction, CL spectra, UV-vis spectra and some other experiments. A flow-injection analysis for the determination of nickle(II) ion has been developed, based on the catalysis of nickel(II) ion on the CL reaction between potassium manganate produced on-line and luminol under alkaline condition. Under the optimum conditions, the SCL intensity is linear with the concentration of nickel(II) ion in the range of 8.0-200.0 µg L-1 and 0.2-2.0 mg l-1. The RSD was 4.5% for 11 determinations of 250 µg L-1 nickel(II) ion and the detection limit (3σ) for nickel(II) ion was 0.33 µg l-1. The method was applied to determine nickel(II) ion in synthetic samples with satisfactory results.

"Use Of 1,3-diaminepropane-3-propyl Grafted Onto A Silica Gel As A Sorbent For Flow-injection Spectrophotometric Determination Of Copper (II) In Digests Of Biological Materials And Natural Waters"
Spectrochim. Acta A 2005 Volume 62, Issue 1-3 Pages 398-406
Sandra V.M. de Moraes, Jorge L. Brasil, Caroline D. Milcharek, Lucas C. Martins, Marina T. Laranjo, Márcia R. Gallas, Edílson V. Benvenutti and Eder C. Lima

Abstract: The 1,3-diaminepropane-3-propyl-anchored silica gel (DAPPS) was successfully employed as a sorbent in a spectrophotometric flow system for the pre-concentration of Cu2+ in digests of biological materials (maize powder, soybean, citrus leaves, corn stalks) as well as water samples (river, stream, streamlet, springwater and well). The system presented a minicolumn packed with DAPPS, where the sample solution was passed through it for a period of time, and subsequently, an eluent solution, stripped-out the retained analyte which was further determined with DDTC at 460 nm. The better pre-concentration conditions utilized were: 120 s loading, 60 s elution, 30 s regeneration of the column, loading flow rate 6.5 mL min-1, buffer solution for the pre-concentration and regeneration of the column-borate buffer pH 8.5, elution flow rate 2.3 mL min-1, time of elution 60 s, eluent composition, 0.4 mol L-1 HNO3. Under these conditions, the pre-concentration factor obtained was 36, and the detection limit achieved was 8.4 ng mL-1 in water samples and 0.84 ?g g-1 in biological material. The maximum adsorption capacity of DAPPS to Cu2+ was 0.49 mmol g-1 (31.1 mg g-1) obtained in a batch system. The recovery of copper in the water samples ranged from 96.9 to 102.4% and in the biological materials ranged from 97.0 to 102.6%. © 2005 Elsevier B.V. All rights reserved.

"Flow Injection Kinetic Spectrofluorimetric Determination Of Trace Amounts Of Osmium"
Spectrochim. Acta A 2005 Volume 61, Issue 9 Pages 2239-2244
Bo Tang, Hui Zhang and Yan Wang

Abstract: A flow injection (FI) kinetic spectrofluorimetric method is described for the determination of osmium(IV) and the possible mechanism of catalytic reaction is discussed. The method is based on the fluorescence enhancing reaction of o-vanillin furfuralhydrazone (OVFH) with potassium bromate, which is catalyzed by Os(IV) in water medium at pH 6.10 and 45°C. OVFH is newly synthesized and its ionization, IR and elemental analysis are established. Under these experimental conditions, the oxidized product of OVFH has excitation and emission maxima at 337 and 490 nm, respectively. The linear range of this method is 0-600 ng mL-1 with the RSD of 1.2%. The detection limit is 1.0 ng mL-1 of Os(IV). A high analysis rate of 24 samples h-1 is obtained by the FI method. The proposed method is applied successfully to determine Os(IV) in synthetic mixture and mineral samples, and the results are well consistent with the standard values.

"Flow Injection Spectrofluorimetric Study Of The Supramolecular Interaction Between β-cyclodextrin And Dequalinium Chloride And Its Analytical Application"
Spectrochim. Acta A 2005 Volume 61, Issue 9 Pages 2203-2209
Bo Tang, Baoxiu Jia and Xifeng Shi

Abstract: The supramolecular interaction of dequalinium chloride (DQC) and β-cyclodextrin has been studied by flow injection spectrofluorimetry. The results showed that β-CD reacted with DQC to form a 1:1 host:guest complex with an apparent association constant of 4.99 X 102 L mol-1. Based on the enhancement of the fluorescence intensity of DQC, a flow injection sepctrofluoremetric method for the determination of DQC in bulk aqueous solution in the presence of β-CD was developed. The linear range was 0.0412-30.00 µg mL-1. The detection limit was 12.3 ng mL-1 with a sampling rate of 80 h-1. There was no interference from the excipients normally used in tablets and serum compositions. The proposed method was successfully applied to the determination of DQC in tablets and serum.

"Application Of Light-absorption Ratio Variation Approach As An Optimum Spectrophotometry To Determination Of Mn(II) In Ng Ml-1 Level Using A Competitive Replacement Complexation"
Spectrochim. Acta A 2005 Volume 61, Issue 3 Pages 447-454
Hong-Wen Gao, Sheng-Yi Zhang, Hong-Yan Wang, Si-Qing Xia and Ya-Lei Zhang

Abstract: The light-absorption ratio variation approach (LARVA) which produces an outstandingly increasing of analytical sensitivity was applied to the quantitative detection of ultramicro amounts of Mn(II) by light-absorption spectrometry using the competitive replacement complexation among 1,5-di(2-hydroxy-5-sulfophenyl)-3-cyanoformazan (DSPCF), Zn(II) and Mn(II) in the presence of o-phenanthroline (OPTL). Not only masks OPTL foreign metal ions but also seriously sensitize the competitive complexation. All the binary and ternary complexes were characterized by the break point approach. Results have shown that the limit of detection (3s) of Mn(II) is only 0.7 ng mL-1. This method has been applied to analysis of water quality with satisfactory results.

"Photothermal Spectrometry For Detection In Miniaturized Systems: Relevant Features, Strategies And Recent Applications"
Spectrochim. Acta A 2004 Volume 60, Issue 12 Pages 2793-2801
K. Abbas Ghaleb and J. Georges

Abstract: There is a growing interest in using miniaturized analytical devices because they allow to execute the different steps of an analytical process within very short times and with drastic reduction in the amounts of solvents, reagents and samples. As for capillary electrophoresis, these systems require detectors which are sensitive, versatile and adaptable to very small detection volumes. In this respect, photothermal spectrometry which is complementary to fluorescence seems to be a promising detection method. This review describes the basic principle of photothermal spectrometry along with the related methods based on colinear-beam or crossed-beam configuration of the pump and probe lasers. Two experimental set ups especially designed for microfluidic systems as well as for capillary electrophoresis are described. Their characteristics and key features are discussed and the main applications are outlined.

"Flow Injection Chemiluninescence For Detecting Picogram Amounts Of Dobesilate In Human Urine"
Spectrochim. Acta A 2004 Volume 60, Issue 10 Pages 2377-2382
Zhenghua Song, Qiaoli Yue and Changna Wang

Abstract: A sensitive method for the determination of dobesilate in pharmaceutical preparations and human urine is described by using controlled-reagent-release technology. The method entailed the use of luminol and periodate, which are immobilized on anion exchange resin and react in alkaline medium, giving chemiluminescence (CL) at 425 nm. Dobesilate was detected by measuring the decrease of CL intensity, and which was observed linear over the dobesilate concentration range of 10^-600 pg mL-1, and the limit of detection was 3.5 pg mL-1 (3s) and a relative standard deviation of less than 3.0%. At a flow rate of 2.0 mL min-1, the determination of dobesilate, including sampling and washing, could be performed in 0.5 min, giving a throughput of about 120 times per hour. The proposed method has an extremely low limit of detection down to 3.5 pgml-1, thus it can be applied directly in the assay of human urine without any pre-treatment. It was also found that the dobesilate concentration reached its maximum after orally administrated for 3.5 hrs, and the excretion ratio in 24h was 58.8% in the body of volunteers.

"Highly Selective Spectrophotometric Flow-injection Determination Of Trace Amounts Of Bromide By Catalytic Effect On The Oxidation Of M-cresolsulfonephthalein By Periodate"
Spectrochim. Acta A 2004 Volume 60, Issue 8-9 Pages 2053-2057
Ali A. Ensafi, B. Rezaei and S. Nouroozi

Abstract: A new flow-injection method is reported for the determination of bromide. The method is based on catalytic effect of bromide on the oxidation of m-cresolsulfonephthalein by periodate in acidic media. The reaction was followed spectrophotometrically by measuring the decrease in absorbance at 528 nm. The influence of pH, reagent concentration and manifold variables on the sensitivity was studied. Under optimum conditions, a calibration graph was obtained in the range of 0.160-20.00 µg mL-1 bromides with a limit of detection of 0.150 µg mL-1 bromide. The relative standard deviation for ten replicate measurement of 1.0 µg mL-1 bromide was 2.1%. The influence of potential interfering ions on the selectivity was studied. The method successes to measure bromide in the presence of other halide ions. The method was used to measure bromide in river water and tap water.

"Simultaneous Photometric Determination Of Albumin And Total Protein In Animal Blood Plasma Employing A Multicommutated Flow System To Carried Out On Line Dilution And Reagents Solutions Handling"
Spectrochim. Acta A 2004 Volume 60, Issue 3 Pages 579-583
Gilmara C. Luca and Boaventura F. Reis

Abstract: An automatic flow procedure for the simultaneous determination of albumin and total protein in blood plasma samples is proposed. The flow network comprised a set of three-way solenoid valves assembled to implement the multicommutation. The flow set up was controlled by means of a computer equipped with an electronic interface card which running a software wrote in 4.5 performed on line programmed dilution to allow the determination of both albumin and total protein in blood plasma. The photometric methods based on Bromocresol Green and Biuret reagents were selected for determination of albumin and total protein, respectively. Two LEDs based photometers coupled together the flow cells were employed as detector. After the adjustment of the operational parameters the proposed system presented the following features: an analytical throughput of 45 sample processing per hour for two analytes; relative standard deviations of 1.5 and 0.8% (n=10) for a typical sample presenting 34 g L-1 albumin and 90 g L-1 total protein, respectively; linear responses ranging from 0 to 15 g L-1 albumin (r=0.998) and total protein (r=0.999); sample and reagents consumption, 140 µl serum solution, 0.015 mg VBC and 0.432 mg CuSO4 per determination, respectively. Applying the paired t-test between results obtained using the proposed system and reference methods no significant difference at 95 and 90% confidence level for albumin and total protein, respectively, were observed.

"Spectrophotometric Study On The Stability Of Dopamine And The Determination Of Its Acidity Constants"
Spectrochim. Acta A 2003 Volume 59, Issue 13 Pages 3193-3203
A. E. Sánchez-Rivera, S. Corona-Avendaño, G. Alarcón-Angeles, A. Rojas-Hernández, M. T. Ramírez-Silva, and M. A. Romero-Romo

Abstract: The interest in determining the acidity constants of the catecholamines stems from the fact that they play rather an important biological role. The present work reveals the effect of different parameters such as oxygen, light, analysis time and pH on the dopamine oxidation process, where oxygen has an effect on the dopamine oxidation of 40% and up to 20% is attributed to exposure to light as a function of the pH. The application of adequate control on the said parameters (which ensured stability of the dopamine) facilitated the determination of the corresponding three acidity constants, 9.046±0.147, 10.579±0.148 and 12.071±0.069.

"Sequential Flow Injection Determination Of Iodate And Periodate With Spectrophotometric Detection"
Spectrochim. Acta A 2003 Volume 59, Issue 12 Pages 2897-2903
Ali A. Ensafi and M. Arab Chamjangali

Abstract: A flow injection (FI) system is described for the sequential determination of periodate and iodate based on their reaction with iodide at pH 3.5. Two sample plugs were injected into the same carrier stream sequentially. One injection is for the iodate determination and the other for the sum of iodate and periodate determination. For iodate determination, molybdate solution buffered at pH of 3.5 was used for selective masking of periodate. The influences of reagent concentrations were studied by a univariable method and the influence of FI manifolds was studied using univariable and simplex method. Periodate and iodate can be determined in the range of 0.050-5.0 and 0.050-10 µg/ml, respectively. The 3s limit of detection was 0.030 and 0.050 µg/ml for periodate and iodate, respectively. The proposed method has been applied for the sequential determinations of periodate and iodate in water samples.

"Flow-injection Chemiluminescence Study Of Ce(IV)–Na2SO3–Tb(III)–fluoquinolone Antibiotic System With DNA"
Spectrochim. Acta A 2003 Volume 59, Issue 11 Pages 2541-2546
Lin Yi, Huichun Zhao, Chunyan Sun, Shilv Chen and Linpei Jin

Abstract: A novel flow injection chemiluminescence (CL) system is developed to determine DNA. According to the fact that DNA linearly quenches the CL intensity of Ce(IV)-Na2SO3-Tb(III)-fluoquinolone antibiotic (FLUQ) system, DNA concentration is determined. The calibration graphs are linear in the range of 0.04-10 µg/ml (for both natural and denatured DNA), and the 3s limits of detection are 7.8 ng/ml (natural DNA) and 9.5 ng/ml (denatured DNA). According to fluorescence spectrum and CL spectrum, and through studying the reaction of Ce(IV)-Na2SO3-Tb(III)-FLUQ with nucleotides and bases, we conclude that DNA counteracts the energy transfer from FLUQ to Tb(III), and this function is related to both bases and phosphate groups in DNA.

"Flow Injection Spectrophotometric Determination Of Periodate And Iodate By Their Reaction With Pyrogallol Red In Acidic Media"
Spectrochim. Acta A 2002 Volume 58, Issue 13 Pages 2835-2839
Ali A. Ensafi and M. Arab Chamjangali

Abstract: A simple and efficient flow injection method was used with good results to determine periodate and iodate in water. The-method is based on the reaction of periodate or iodate with pyrogallol red in sulfuric acid media. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of pyrogallol red at 470 nm. The chemical and FIA variables were established using the univariate and simplex optimization methods. The calibration curve was linear over the concentration ranges of 0.8-73.0 and 2.0-100.0 muM for IO4- and IO3-, respectively. The detection limits were 0.7 and 1.0 muM for IO4- and IO3-, respectively. The sample throughput was 20±5 h-1. The influence of potential interfering ions in the determination of the anions was tested. The relative standard deviations for 4.20 and 5.73 muM periodate and iodate were 1.8 and 2.2%, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.

"Chemiluminescence Flow Sensor For Folic Acid With Immobilized Reagents"
Spectrochim. Acta A 2001 Volume 57, Issue 13 Pages 2567-2574
Zhenghua Song and Xin Zhou

Abstract: A novel chemiluminescence (CL) sensor for folic acid combined flow injection (FI) technology was presented in this paper. The analytical reagents involved in the CL reaction, including luminol and hexacyanoferrate(III), were both immobilized on an anion-exchange column in FI system. The CL signal produced by the reaction between luminol and hexacyanoferrate(III), which were eluted from the column through sodium phosphate injection, was decreased in the presence of folic acid, The CL emission was correlated with the folic acid concentration in the range from 0.01 to 15 µg mL-1, and the detection limit was 3.5 ng mL-1 folic acid (3s). At a flow rate of 2.0 mL min-1, including sampling and washing, could be performed in 2 min with a relative standard deviation of < 2.5%. The flow sensor could be reused more than 300 times and has been applied to the analysis of folic acid in pharmaceutical preparations, and the recovery was from 97.4% to 100.4%. (C) 2001 Elsevier Science B.V. All rights reserved.

"Spectrofluorimetric Flow Injection Determination Of Trace Amounts Of Periodate"
Spectrochim. Acta A 2001 Volume 57, Issue 9 Pages 1739-1743
Ali A. Ensafi and G. Bagherian Dehahgi

Abstract: A sensitive, rapid and selective procedure is proposed for the flow injection determinations of periodate by spectrofluorometric detection. The method is based on the reaction of periodate with Alizarin Navy Blue in basic solution. The reagents and manifold variables influence on the sensitivity have been investigated and the optimum conditions are established. Periodate can be determined for the range of 0.250-5.00 µg mL-1 with a limit of detection of 0.08 µg mL-1, and with a sample rate of 15±2 samples h-1. The relative standard deviations for eight replicate determination of 0.500 and 5.00 µg mL-1 was 1.3 and 1.1%, respectively. Periodate can be determined in the presence of iodate and bromate. The proposed method was used to determination of periodate in water samples. (C) 2001 Elsevier Science B.V. All rights reserved.

"Flow Injection Catalytic Determination Of Ruthenium With Spectrophotometric Detection"
Spectrochim. Acta A 2000 Volume 56, Issue 8 Pages 1583-1588
Ali A. Ensafi and M. Arab Chamjangali

Abstract: A new flow injection catalytic method was described for the determination of ruthenium(III) based on its catalytic effect on the oxidation of brilliant cresyl blue (BCB) by periodate in acidic media. The reaction was followed spectrophotometrically by measuring the absorbance of the dye at 635 nm. Under optimum conditions, ruthenium can be determined in the range of 1.0-100.0 ng mL-1 with a relative standard deviation of 1.1% and with a limit of detection of 0.70 ng mL-1. The influence of reagent and manifold variables were studied and optimized. The method was tested for the determination of ruthenium(III) in some synthetic mixtures.