Full Paper Voltammetric Determination of Phenylglyoxylic Acid in Urine Using Graphite Composite Electrode Toma ´s ˇ Navra ´til, a * Zden ˇkaS ˇ enholdova ´ , b Kumaran Shanmugam, a Jir ˇí Barek c a J. Heyrovsky ´ Institute of Physical Chemistry, Dolejs ˇkova 3, CZ-182 23 Prague 8, Czech Republic *e-mail: navratil@jh-inst.cas.cz b Department of Occupational Medicine, Toxicological Laboratory, First Faculty of Medicine, Charles University, Na Bojis ˇti 1, 128 00 Prague 2, Czech Republic e-mail: zdenka.senholdova@lf1.cuni.cz c UNESCO Laboratory of Environmental Electrochemistry, Department of Analytical Chemistry, Charles University, 128 43 Prague 2, Czech Republic e-mail: barek@natur.cuni.cz Received: August 31, 2005 Accepted: August 31, 2005 Abstract A composite electrode prepared from graphite powder and epoxy resin was applied as a working electrode for the determination of phenylglyoxylic acid (one of the metabolites of styrene) in human urine. Cathodic differential pulse stripping voltammetry was used and optimum conditions have been found giving the limit of determination about 5 mg L 1 . All results were compared with those obtained using hanging mercury drop electrode. For the confirmation of suggested mechanism of the electrochemical reaction the elimination voltammetry with linear scan was used. Keywords: Graphite composite electrode, Voltammetry, Styrene, Vinylbenzene, Phenylglyoxylic acid, Elimination voltammetry with linear scan, EVLS DOI: 10.1002/elan.200503394 Dedicated to Professor Karel S ˇ tulík on the Occasion of His 65 th Birthday 1. Introduction Styrene (vinylbenzene) presents very important starting compound for the production of the wide range of plastics (polystyrene, styrene-acrylonitrile etc.). The International Agency for Research on Cancer (IARC) [1] sorted styrene to the group 2B (The agent (mixture) is possibly carcino- genic to humans. The exposure circumstance entails expo- sures that are possibly carcinogenic to humans.). Therefore, it is necessary to monitor the concentration of this substance in the environmental air as well as human exposition to it by monitoring its metabolites in body fluids. Its metabolite styrene-7,8-oxide is carcinogenic and mutagenic (IARC – Group 2A – probably carcinogenic to humans) [1]. Styrene oxide can react with nucleotides and three of four formed nucleotides are mutagenic [2]. Mandelic acid, benzoic acid, and phenylglyoxylic acid (PGOA) are three main metabo- lites of styrene. It is recommended to monitor the exposure to styrene by the determination of phenylglyoxylic and mandelic acid in human urine, and of styrene in human blood (so called biological exposition test). The American Conference of Governmental Industrial Hygienists (ACGIH) has publish- ed Biological Exposure Indices (BEI) for styrene in urine: the concentration of mandelic acid plus phenylglyoxylic acid in urine at the end of the working shift should be less then 400 mg g 1 creatinine [3]. The limit value of this biological exposition test in Czech Republic was set to 600 mg of phenylglyoxylic and mandelic acids per 1 g of creatinine in human urine and at the same time the maximal concen- tration of mandelic acid can amount to 400 mg per 1 g of creatinine [4, 5]. The excretion of mandelic acid from the human body can be decelerated due to various factors, so it is recommended to monitor the exposure to styrene by the determination of phenylglyoxylic acid in urine only. The normal value of creatinine in urine varies between 0.5 and 2 g L 1 [5], i.e., the determined concentration value of the phenylglyoxylic acid should be divided or multiplied maximally by 2, nevertheless, voltammetric methods can reach the concentration level two or more orders of magnitude lower than the above cited limits. So it is not necessary to recalculate the results to the creatinine concentrations. Many other methods have been used for determination of phenylglyoxylic acid and mandelic acid: HPLC (e.g., [6]), gas chromatography (GC) after derivatization (e.g., [7]), fluorimetric analysis using extraction (e.g., [8]). Limits of detection of all of these methods are practically equal, in order of mg L 1 . These methods are time-consuming (derivatization, extraction, etc.) and instrumentally more 201 Electroanalysis 18, 2006, No. 2, 201 – 206 # 2006 WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim