A Miniaturized Stepwise Injection Spectrophotometric Analyzer.

A novel micro-stepwise injection analyzer (μSWIA) has been developed for the automation and miniaturization of spectrophotometric analysis. The main unit of this device is a mixing chamber (MC) connected to the atmosphere. This part of the μSWIA provides rapid and effective homogenization of the reaction mixture components and completion of the reaction by means of gas bubbling. The μSWIA contained a rectangular labyrinth channel designed in way allowing one to eliminate bubbles by moving a solution from the MC to an optical channel. The light-emitting diode (LED) was used as a light emitter and the analytical signal was measured by a portable spectrophotometer. Fluid movement was attained via the use of a computer-controlled syringe pump. The μSWIA was successfully used for the spectrophotometric determination of cysteine in biologically active supplements and fodder by using 18-molybdo-2-phosphate heteropoly anion (18-MPA) as the reagent.