On-line determination of trace sulfur dioxide in air by integrated microchip coupled with fluorescence detection

A microchip-based method was developed for on-line determination of trace sulfur dioxide (SO2) in air. Gaseous SO2, which diffused through the porous glass materials on the microchip, was absorbed into an absorption solution of triethanolamine (TEA) as sulfite ions and reacted with N-(9-acridinyl)maleimide (NAM), which was used as a fluorescent reagent. The fluorescence of NAM-sulfite in micro-fluidic channel was detected. The calibration curve of sulfite ions in the range of 1.5–30 μmol/L (SO2 3–60 ppbv) showed a linear relation R2 = 0.995, and the relative standard deviation (R.S.D.) was 1.9% for 10 μmol/L sulfite ions in five measurements. The entire measurement procedure was achieved by the integrated microchip, and the consumption of reagents was drastically reduced. It was satisfactory to apply this method to determine on-line the SO2 level in the air.