From Sample Processing to Quantification: A Full Electrochemical Approach for Neutral Analyte Derivatization, Capillary Electrophoresis Separation, and Contactless Conductivity Detection

• Published in: Analytical chemistry (Washington) Vol. 84; no. 18; pp. 7599 - 7602
• Main Authors: Santos, Mauro Sérgio Ferreira, Lopes, Fernando Silva, Vidal, Denis Tadeu Rajh, do Lago, Claudimir Lucio, Gutz, Ivano Gebhardt Rolf
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 18.09.2012
• Subjects: Alcohol; Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Chromatography; Conductivity; Electrochemical methods; Electrodes; Exact sciences and technology; Fluid mechanics; Gas chromatographic methods; Other chromatographic methods; Oxidation; Electrochemical method; Alcohol; Activation; Flame ionization detector; Time; Derivatization; Pentanols; Stopped flow method; Regulation(control); Efficiency; Platinum; Model compound; Detection limit; Electrochemical reaction; Acid medium; Quantitative analysis; Automation; Ethanol; Aliphatic compound; Capillary electrophoresis; Sample; Concentration; Flame ionization detection; Propanol; Automatic processing; Gas chromatography; Sample cell; Conductometry; Simultaneous measurement; Frequency analysis; Carboxylate; Butanol; Application; Non contact measurement
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac3019312

A thin-layer electrochemical flow cell coupled to capillary electrophoresis with contactless conductivity detection (EC-CE-C4D) was applied for the first time to the derivatization and quantification of neutral species using aliphatic alcohols as model compounds. The simultaneous electrooxidation of four alcohols (ethanol, 1-propanol, 1-butanol, and 1-pentanol) to the corresponding carboxylates was carried out on a platinum working electrode in acid medium. The derivatization step required 1 min at 1.6 V vs. Ag/AgCl under stopped flow conditions, which was preceded by a 10 s activation at 0 V. The solution close to the electrode surface was then hydrodynamically injected into the capillary, and a 2.5 min electrophoretic separation was carried out. The fully automated flow system operated at a frequency of 12 analyses per hour. Simultaneous determination of the four alcohols presented detection limits of about 5 × 10–5 mol L–1. As a practical application with a complex matrix, ethanol concentrations were determined in diluted pale lager beer and in nonalcoholic beer. No statistically significant difference was observed between the EC-CE-C4D and gas chromatography with flame ionization detection (GC-FID) results for these samples. The derivatization efficiency remained constant over several hours of continuous operation with lager beer samples (n = 40).