Voltammetric Determination of Phenylglyoxylic Acid in Urine Using Graphite Composite Electrode

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 À1 . 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.

Nontraditional Electrode Materials in Environmental Analysis of Biologically Active Organic Compounds

“…Insulator phase should be prepared separately [122,149]. Both parts are mixed in desired ratio [122,148,149] (it depends on determined analyte and supporting electrolyte, e.g., graphite -epoxide electrodes contain from 20 to 60% [125], in Ag or Au composite electrodes the amount of metal is about 10 to 30% [132,148]). Content of bulk modifiers varies usually from tenths to tens per cents, e.g., graphite content in silver-methacrylate electrode is about 15% [146].…”

“…In some cases it is necessary to choose proper electrode body material, which would not be damaged by solvent of the analyte (e.g., methanol, which damages in higher concentrations epoxy resin). In the first step the appropriate amount of conductor phase (e.g., silver) is homogenized with a modifier (e.g., graphite, metallic powder) (particle size of metallic parts from 5 -50 mm and of graphite below 50 mm usually [125,148]). Insulator phase should be prepared separately [122,149].…”

“…According to the classification published in [120] they belong to the group of composite electrodesrandom ensembles-dispersed-solid. Insulator phase is usually represented by polymeric (acrylic polymer [122,123], epoxy resin [124,125], polyvinyl chloride (PVC) [126,127], teflon [124,128], vinylacetate [124], polyester [124], polyethylene [124] [122,129,130], gold [131], etc.) or by other nonmetallic conducting material (e.g., graphite powder [132]).…”

“…[141,142] regeneration usually depends on type and quantity of undesired compounds on the surface. The regeneration is carried out by periodical switching between positive and negative potentials in the given base electrolyte ten or even hundred times, or by insertion of constant positive or negative potential for a time period from tens to hundreds seconds or by combination of both mentioned processes [125]. This regeneration can take a few minutes.…”

“…In the case of flow-through systems the surface passivating compounds are removed by flowing medium. In the case of batch analysis, it is necessary to perform either repolishing of the electrode surface, e.g., by a filter paper, or it is necessary to perform electrochemical regeneration of the surface [125,131,149]. Procedure of the preceded electrochemical Table 5.…”