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.