Electrochemical Study of Gold Microelectrodes Modified with PEDOT to Quantify Uric Acid in Milk Samples

Abstract

A gold microelectrode (10 μm diameter) with an electropolymerized layer of poly(3,4‐ethylenedioxythiophene) (PEDOT) was used to quantify uric acid and investigate the antioxidant profile of milk and flavored milks. Comparisons were made with a bare gold microelectrode and a PEDOT‐glassy carbon macroelectrode (3 mm diameter). Two different electropolymerization processes were undertaken in an aqueous and an organic solution, and superior polymer growth was observed for PEDOT polymerized in lithium perchlorate/propylene carbonate. In the presence of a ferri/ferrocyanide redox couple, diffusion‐controlled redox peaks were observed with the PEDOT‐gold microelectrode rather than the plateau current typical of a bare microelectrode. Likewise, an anodic peak for uric acid was observed at the high surface‐area PEDOT‐gold microelectrode, with evidence for pre‐adsorption of uric acid at the electrode. The linear concentration range for uric acid standards was from 6 to 200 μM, and the limit of detection, limit of quantification, and sensitivity were determined to be 7 μM, 24 μM, and 397 μAμM−1cm2, respectively. Cyclic voltammograms of chocolate and espresso flavored milks exhibited significant contributions from the phenolic compounds present. Peak separation was more clearly defined using the PEDOT‐microelectrode compared to a PEDOT‐glassy carbon macroelectrode.

Electrochemical Methods for the Analysis of Milk

“…Other electrode chemical modifications can be obtained by deposition of metal nanoparticles, ,,− conducting polymers, ,,, and biological active modifiers such as enzymes ,, and aptamers ,,,, on the electrode surface to create a biosensor. Deposition of metal nanoparticles such as nanorods, nanowires, or nanosheets facilitate particular reactions and increase the electron transfer rate between the analyte and electrode. ,− Besides, metal nanoparticles such as gold nanoparticles can be an excellent scaffold for specific attachments for DNA or proteins (e.g., antibody, enzyme, etc.)…”

“…The developed sensor was used to quantify UA in 36 commercial milk samples (no pretreatment required) and compared to results obtained from HPLC after appropriate pretreatments, and the average difference was only around 6% between the two methods . In a further study, this chemical modification with PEDOT was applied to a commercial gold microelectrode surface to detect UA antioxidant in milk and flavored milks, which significantly increased the current density compared with a PEDOT-modified glassy carbon macroelectrode …”

“…Other electrode chemical modifications can be obtained by deposition of metal nanoparticles, 34,85,120−122 conducting polymers, 72,118,119,123 and biological active modifiers such as enzymes 85,108,124 and aptamers 125,98,126,85,34 on the electrode surface to create a biosensor. Deposition of metal nanoparticles such as nanorods, nanowires, or nanosheets facilitate particular reactions and increase the electron transfer rate between the analyte and electrode.…”

“…72 In a further study, this chemical modification with PEDOT was applied to a commercial gold microelectrode surface to detect UA antioxidant in milk and flavored milks, which significantly increased the current density compared with a PEDOT-modified glassy carbon macroelectrode. 123 Organic, Nitrogen-and Aldehyde-Containing Compounds: Amino Acids, Folic Acid, Urea, Melamine, Vanillin, Coumarin. Some amino acid residues of milk proteins, such as tryptophan, tyrosine, lysine, histidine, and methionine are also antioxidative, functioning by the quenching of free radicals.…”

Development and validation of an ion chromatography‐ultraviolet method for determination of uric acid in the delactosed permeate

“…Various organic acids including citric, lactic, orotic, hippuric, and uric acids are present in delactosed permeate [4]. Uric acid (2,6,8-tridroxypurine) is formed from the purine derivatives in normal bovine biochemical metabolism [5][6][7][8][9]. It is an important endogenous antioxidant which is believed to reduce the oxidation Article Related Abbreviations: CV, coefficient of variation; IC, ion chromatography; LLOQ, lower LOQ; QC, quality control.…”