Flow-injection responses of diffusion processes and chemical reactions

The technique of flow-injection analysis (FIA), now 25 years old, offers un ique analytical methods that are fast, reliable and consume an absolute min imum of chemicals. These advantages together with its inherent feasibility for automation warrant the future application of FIA as an attractive tool of automated analytical chemistry. The need for an even lower consumption o f chemicals and for computer analysis has motivated a study of the FIA peak itself, i.e., a theoretical model that provides detailed knowledge of the FIA profile was developed. It was shown that the flow in a FIA manifold may be characterised by a diffusion coefficient that depends on the flow rate, denoted as the kinematic diffusion coefficient. The description was applie d to systems involving species of chromium, both in the case of simple diff usion and in the case of chemical reaction. It is suggested that the descri ption may be used in the resolution of FIA profiles to obtain information a bout the content of interferences, in the study of chemical reaction kineti cs and to measure absolute concentrations within the FIA-detector cell.