CONVECTION-DIFFUSION THEORY OF SAMPLE DIS PERSION IN FLOW-INJECTION ANALYSIS SYSTEM

Two methods were used to solve the convection-diffusion equation which is appropriate to straight single-tube Flow Injection Analysis (FIA) system without chemical reaction, and the concentration distribution o f the slug-injected sample after dispersing in the tube was obtained. F-Curve was thereby obtained. Effects of inner radius of tube, length of reaction tube, length of sampling tuber flow rate and diffusion coe fficient on peak shape and dispersion were discussed. The relationship between half peak width and diffusion coefficient was solved by numer ical method. Two methods to determine diffusion coefficient by FIA wer e suggested. This paper offered a theoretical guideline for design of FLA system, selection of indicator and operating condition.