title: From sample processing to quantification: a full electrochemical approach for neutral analyte derivatization, capillary electrophoresis separation, and contactless conductivity detection.
abstract: A thin-layer electrochemical flow cell coupled to capillary electrophoresis with contactless conductivity detection (EC-CE-C(4)D) 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-C(4)D 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).
authors.affiliation: Instituto de Química, Universidade de São Paulo, Brazil.
authors.forename: Mauro Sérgio Ferreira
authors.initials: MS
authors.lastname: Santos
authors.forename: Fernando Silva
authors.initials: FS
authors.lastname: Lopes
authors.forename: Denis Tadeu Rajh
authors.initials: DT
authors.lastname: Vidal
authors.forename: Claudimir Lucio
authors.initials: CL
authors.lastname: do Lago
authors.forename: Ivano Gebhardt Rolf
authors.initials: IG
authors.lastname: Gutz