Flow injection system for kinetic determinations based on the use of two serial injection valves

Abstract

A configuration including two serial injection valves is reported. The system inserts two zones of the same sample simultaneously into a channel, which results in a two-peak recording. The physical (injection of a dye) and physico-chemical (use of two chemical systems with different reaction rates) behaviour of this configuration was studied. The manifold was applied to individual kinetic and differential kinetic determinations of cobalt and nickel based on their different complexation rates with 2-hydroxybenzaldehyde thiosemicarbazone. In the individual determinations the peak-height or -area measurements made at two different reaction times allow one to establish determinative methods based on area or height increments, performing a statistical study for contrastive purposes with both types of measurements. The differential kinetic method was tested on the resolution of mixtures within a wide concentration range and by a statistical study of the reproducibility, using very different ratios of the two analytes.