Fluorometric determination of sulfite and nitrite in aqueous samples using a novel detection unit of a microfluidic device.

On-chip fluorescence determination of sulfite and nitrite with N-(9-acridinyl)maleimide (NAM) and 2,3-diaminonaphthalene (DAN) has been developed using a novel fluorescence detection unit for microchip analysis. Usually, these fluorescence reagents are derivatized and detected separately in microchip analysis because different fluorescence wavelengths are emitted. The proposed fluorescence detection unit has optical fibers with no optical filter, and plural wavelengths of fluorescence were detected sensitively, even in the microchip. In this study, the simultaneous determination of sulfite and nitrite in environmental samples was performed with a polymer microchip analysis system. The calibration curves of sulfite and nitrite showed linear relations (R2 = 0.998 (sulfite) and R2 = 0.990 (nitrite)), and the relative standard deviations (RSD) for 4 runs were 2.1% (20 microM sulfite) and 1.3% (20 microM nitrite), respectively. The proposed method was applied to the recovery test of sulfite and nitrite in environmental samples.