Development of a Simple and Compact Flow-injection Analysis System Using an LED-based Absorbance Detector and Micro-ring Pumps

We have developed a simple and compact flow-injection analysis (FIA) system using an LED base absorbance detector and micro-ring pumps. The detector has four LEDs and can measure absorbance corresponding to each LED wavelength (465 nm, 525 nm, 625 nm, and 850 nm) sequentially. A micro-ring pump is a single roller pump whose flow contains pulsation, which imposes some noises on a flow signal. It is notable in the case that a reagent solution includes an organic solvent or colored reagent. A refractive index difference between a carrier and sample produces a pseudo peak called the Schlieren effect. Dual wavelength measurement techniques and the optimization of the reagent composition could suppress those noises. We applied this FIA system to measure nitrogen as nitrate, phosphorus as phosphate, and chromium(VI) according to the modified procedures of JIS K 0170.