Application of a micro multiphase laminar flow on a microchip for extraction and determination of derivatized carbamate pesticides.

Determination of carbamate pesticides such as carbaryl, carbofuran, propoxur and bendiocarb was demonstrated on a microchip with newly designed microchannels developed for efficient solvent extraction. The pesticides were hydrolyzed to corresponding naphthols, coupled with p-nitrobenzenediazonium fluoroborate reagent, and then extracted into 1-butanol as colored azo derivatives and detected with a thermal lens microscope. Optimum flow rates for the aqueous and organic phases were evaluated in the continuous-flow chemical process established in the microchip. The calibration lines showed good linearity in the range of concentrations of 0.03 - 3 ppm (10(-7) - 10(-5) M) and a mass detection limit down to a nanogram level was achieved that is at least two orders of magnitude lower than the LODs for conventional spectrophotometric methods. Azo derivatives of the pesticides were successfully separated and identified by micellar electrokinetic chromatography (MEKC) using a sample prepared on a bulk scale.