Investigation of Flow Injection Analysis in Terms of Segment Flow, Double Peaks and Friction

A theoretical investigation of flow injection analysis (FIA) has been developed and it was tested experimentally on the online reaction between chromate and 1,5 diphenylcarbazide (DPC). The flow is of segment type and the injected sample expands exponentially with time and it expands both in upstream and the downstream direction. The symmetry of the expansion is destroyed only by transfer of solute molecules from the front to the rear of the segment, as caused by friction. It was found that the FIA peak, fundamentally, consists of two individual peaks that develop upon sample injection, as a results of sample molecules mixing with the carrier, predominantly at the front of the segment and at the rear of the segment. Useful equations kinetics were obtained for a description of the FIA trace and for providing characteristic time parameters of the system.by approximating the segment with a retangular shape and convoluting with the expansion. It is shown that the shape of the FIA peak depends on the physical dimensions of the manifold and on a single parameter of friction, as given by (aD). The ability of the model to provide information about chemical kinetics is discussed.