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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Werasak Surareungchai

Abbrev:
Surareungchai, W.
Other Names:
Address:
School of Bioresources and Technology, King Mongkut's University of Technology Thonburi Bangkok 10140 Thailand
Phone:
+66-2-4709732
Fax:
+66-2-4523455

Citations 4

"Poly(vinylferrocene)-poly(ethylene Glycol) Glutamate Oxidase Electrode For Determination Of L-glutamate In Commercial Soy Sauces"
World J. Microbiol. Biotechnol. 2003 Volume 19, Issue 5 Pages 479-485
P. Na Nakorn;M. Suphantharika;S. Udomsopagit;W. Surareungchai

Abstract: An amperometric L-glutamate oxidase (GLOD) electrode based on a multilayer of polymer films was developed for the high selective determination of L-glutamate. The multilayer film consisted of three layers as the following configuration i.e., inner membrane of electropolymerized 1,3-diaminobenzene, middle layer of L-GLOD entrapped in photopolymerized poly(vinylferrocene)-poly(ethylene glycol) hydrogel polymer, and outer dialysis membrane. In this manner, the sensor could eliminate interferences and was able to work at a low potential poised at +0.085 V vs. Ag/AgCl. When used in a flow injection system, the sensor responded to L-glutamate in the range 0.5-8.0 mM, with a sensitivity of 9.48 nA mM-1. The sensor was stable for 5 days of continuous uses (250 assays) and retained 60% activity after 16 days. When used to analyze the L-glutamate contents of a number of different off-the-shelf soy sauces, the sensor gave results in good agreement with the standard colorimetric method.

"Sub-millimolar Determination Of Formalin By Pulsed Amperometric Detection"
Anal. Chim. Acta 2004 Volume 510, Issue 2 Pages 195-201
Sirimarn Ngamchana and Werasak Surareungchai

Abstract: Formalin, formaldehyde in the presence of methanol, was determined by pulsed amperometric detection (PAD). A triple waveform using Edet=-0.3 V (tdet=30 ms), Eoxd=+0.8 V (toxd=200 ms), and Ered=-0.8 V (tred=350 ms) versus Ag/AgCl was applied at a Au electrode for detection in a flow injection (FI) system. The approach was rapid and yielded a sub-millimolar detection limit (0.0129 mM) with a dynamic range up to 100 mM. A precision of 8.8% RSD at 1.0 mM for two hundred repetitive injections by the FI-PAD was obtained, whereas holding at a constant potential (-0.3 V versus Ag/AgCl) for anodic oxidation of formaldehyde caused the response to decrease dramatically after a few measurements. The method developed was used to analyze the formalin contents of water from rinsed samples of vegetables and fruit and ice-melt from seafood, and the method showed good agreement with the liquid chromatography (LC) method.

"Quadruple-pulsed Amperometric Detection For Simultaneous Flow Injection Determination Of Glucose And Fructose"
Anal. Chim. Acta 2001 Volume 448, Issue 1-2 Pages 215-220
Werasak Surareungchai, Wilasinee Deepunya and Porntip Tasakorn

Abstract: A quadruple-potential waveform, at E-det1 = -0.5 V (t(det1) = 240 ms), E-det2 = +0.2 V (t(det2) = 180 ms), E-oxd = + 1.0 V (t(oxd) = 180 ms), and E-red = -0.8 V (t(red) = 300 ms) versus SCE, was employed at a Nafion-coated An electrode for the simultaneous determination of glucose and fructose by flow injection analysis. E-det1 and E-det2 caused the oxidation of glucose and glucose and fructose, respectively. Hence, concentration subtraction could be used to determine both species. Using the FI-PAD, a linear response to glucose at E-det1 was obtained across the concentration range 5-60 mM, with a sensitivity of 2.34 x 10^-7 A mM-1, and the limit of detection of 1.2 mM (S/N = 3). Whereas at E-det2 scaled linearly with either glucose or fructose concentration in the range up to 60 mM, with a sensitivity of 7.50 x 10^-6 A mM-1, and the limit of detection of 0.13 mM (S/N = 3). Interference from other sugars, organic acids, and amino acids were studied. The method developed was used to analyze glucose and fructose contents in five different fruit samples; the method showed good agreement with the standard liquid chromatographic method.
Glucose

"Dual Electrode Signal-subtracted Biosensor For Simultaneous Flow Injection Determination Of Sucrose And Glucose"
Anal. Chim. Acta 1999 Volume 380, Issue 1 Pages 7-15
Werasak Surareungchai, Supinda Worasing, Pornpimol Sritongkum, Morakot Tanticharoen and Krissanapong Kirtikara

Abstract: A multi-enzyme electrode obtained by a two-step immobilization of the enzymes glucose oxidase, mutarotase and invertase was developed for the determination of sucrose. Glucose oxidase was entrapped in a poly-1,3-diaminobenzene film on a platinum electrode by electrochemical polymerization and a combination of mutarotase and invertase was cross-linked over the electrode via bovine serum albumin and glutaraldehyde. The sucrose concentration was determined from hydrogen peroxide oxidation at +0.7 V vs. Ag/AgCl. This immobilization method minimized interference from ascorbic acid. A second electrode, for glucose only, was constructed containing inactive invertase. This gave an almost identical glucose response to the sucrose sensor and hence could be used for signal subtraction. In this manner, sucrose could be determined in the presence of glucose at higher concentrations. The influence of enzyme content, pH, temperature, and optimum operational conditions for use in a flow injection analysis (FIA) system were determined. When used in FIA, the sensor responded to sucrose in the range 1-300 mmol l-1. The sensor was stable for 15 h of continuous use (150 assays) and retained 70% activity after 30 days. When used to analyze the sucrose and glucose contents in a number of different soft drinks, the sensor showed good agreement with the standard liquid chromatography (LC) method.
Sucrose Glucose Soft drink Amperometry Immobilized enzyme Optimization Method comparison Interferences