Micro-multiphase laminar flows for the extraction and detection of carbaryl derivative Original Research Article

A new solvent extraction concentration method utilizing microchip technology has been developed. As an important application of this system, carbaryl determination with thermal lens microscope detection was demonstrated. Carbaryl pesticide was hydrolyzed in an alkaline medium to 1-naphthol, was coupled with diazotized trimethylaniline, and, then, was extracted to toluene as a colored azo dye. Two microchips with modified complex-shape microchannels were used for mixing, reaction, extraction, and detection. A thermal lens microscope was used for the detection of the colored product. Optimum conditions for aqueous phase and organic phase flow rates inside the microchannels were identified. The calibration line indicated good linearity for concentrations of 3.4 × 10−7 to 3.5 × 10−6 M and a detection limit of 7 × 10−8 M was obtained. This limit of detection is at least two orders less than LODs for conventional spectrophotometric methods. The results with the present integrated system suggested there was a good potential for implementing an on-site carbaryl analysis system.