Electrochemically synthesized polymers in molecular imprinting for chemical sensing

This critical review describes a class of polymers prepared by electrochemical polymerization that employs the concept of molecular imprinting for chemical sensing. The principal focus is on both conducting and nonconducting polymers prepared by electropolymerization of electroactive functional monomers, such as pristine and derivatized pyrrole, aminophenylboronic acid, thiophene, porphyrin, aniline, phenylenediamine, phenol, and thiophenol. A critical evaluation of the literature on electrosynthesized molecularly imprinted polymers (MIPs) applied as recognition elements of chemical sensors is presented. The aim of this review is to highlight recent achievements in analytical applications of these MIPs, including present strategies of determination of different analytes as well as identification and solutions for problems encountered

Simultaneous RP-LC determination of additives in soft drinks

A reverse-phase HPLC method for the simultaneous determination of the main artificial sweeteners, preservatives and dyes present in soft drinks is proposed. It involves the use of a 10 mu m LiChrosorb RP18 column and a binary eluent consisting of aqueous 0.1 M phosphate buffer (pH 4.0) added with methanol, according to a suitable gradient elution program. Good separations were obtained within less than 20-min run-time, with a satisfactory precision. The sensitivity of spectrophotometric detection was optimised by adopting a wavelength switching technique, thus achieving for all the additives considered detection limits ranging from 0.1 to 3.0 mg L-1, well below the maximum permitted levels. The method was applied to some commercial soft drinks, whose analysis required minimum pre-treatment before direct injection

A modified electrode for the electrochemical detection of biogenic amines and their amino acid precursors separated by microchip capillary electrophoresis

The use of a mixed-valent ruthenium oxide/hexacyanoruthenate polymeric film electrochemically deposited onto glassy carbon electrodes is proposed here for the detection of biogenic amines and their amino acid precursors, following their separation by microchip capillary electrophoresis. The ability of this ruthenium coating to electrocatalyze the oxidation of aliphatic and heterocyclic amines, as well as their amino acid precursors, was checked by using ethanolamine, tryptamine and tryptophane as prototype compounds and adopting a 25mM sulphuric acid as the electrolyte in the detection cell, where a constant potential of 1.05 V versus Ag/AgCl, 3M KCl was applied to the modified working electrode. Optimization of parameters affecting both detection and separation steps led to satisfactory separations when performed by using a 20mM phosphate running buffer (pH 2.5) and applying a high voltage of 2.5 kV both in the separation and in the electrokinetic injection (duration 4 s). The recorded peaks were characterized by good repeatability (RSDr3.6%), high sensitivity and a wide linear range. Detection limits of 23 mM (1.4 mg/L), 27 mM (4.3 mg/L) and 34 mM (6.8 mg/L) were inferred for ethanolamine, tryptamine and tryptophane, respectively. The approach proposed here was also applied for the analysis of some double malt dark beers spiked with a controlled amount of the analytes considered

Simultaneous determination of derivatized light aldehydes by microchip electrophoresis with electrochemical detection

A method, based on microchip electrophoresis with electrochemical detection, has been developed for the simultaneous determination of light aliphatic aldehydes (acetaldehyde, propionaldehyde, butyraldehyde and hexylaldehyde) derivatized with 2,4-dinitrophenylhydrazine (DNPH). Optimal conditions for the derivatization reaction, providing recoveries of 70 +/- 1.8% for all analytes, were identified by application to real samples, consisting of vegetable oils enriched with known amounts of the aldehydes considered. DNPH hydrazones thus obtained in acetonitrile solution were added to the electrophoresis running medium consisting of a 15 mM borate buffer (pH 9.2) added with 25 mM of sodium dodecyl sulfate and 35% (v/v) of acetonitrile. Factors affecting both separation and electrochemical detection were examined and optimised, with best performance achieved by using the running medium above and applying a voltage of 2250V in both separation and electrokinetic injection. Under these optimal conditions, the target analytes could be separated and detected within 350 s by applying a detection potential of -1.0V (vs. Ag/AgCl) to the glassy carbon working electrode. The recorded peaks were well separated and characterized by good repeatability (RSD = 1.6-3.8%), high sensitivity and a wide linear range. Detection limits of 4.5, 6.6, 6.8,13.1 mu M were obtained for acetaldehyde-DNPH, propionaldehyde-DNPH, butyraldehyde-DNPH and hexylaldehyde-DNPH derivatives, respectively