Miniaturized fluorescence detection chip for capillary electrophoresis immunoassay of agricultural herbicide atrazine

This paper reports a miniaturized fluorescence detection chip for capillary electrophoresis immunoassay of atrazine, which effectively reduces the size of fluorescence detection system. The photodiode with fluorescence filter was embedded in PDMS (polydimethylsiloxane) microfluidic chip and was placed just below the microfluidic channel. This detection chip is only few mm thick without loss of fluorescence due to the proximity of photodiode and channel. To investigate the feasibility of in situ detection of agricultural herbicide, atrazine was detected using capillary electrophoresis immunoassay in microfluidic chip. Mixture of 570 nM fluorescence-labeled atrazine (Ag*) and 700 nM anti-atrazine antibody (Ab) was injected and separated in 25 mm long microfluidic channel. The separated peaks of Ab-Ag* immunocomplex and Ag* were detected by the miniaturized detector and the change of peak magnitude was also observed with the variation of Ab concentration. The result was verified with those of external PMT (photomultiplier tube) and commercial capillary electrophoresis system. Hence, we have demonstrated the feasibility of portable CE immunoassay of atrazine with on-chip fluorescence detector.