Flow-injection analysis based on substitution reactions and differential spectrophotometry

A new method of photometric detection is proposed for flow-injection analys is based on substitution reactions in systems metal-complexing agent-metall ochrome indicator. The method consists in the use of metal buffer and ligan d buffer solutions for the adjustment to 100% and zero transmittance in the photometric scale, respectively, according to the principles of differenti al spectrophotometry. It is shown that the best results in extending the sc ale of spectrophotometric detector are obtained using solutions with low bu ffer capacity at approximately equal molar concentrations of the complexing agent and the indicator Depending on the ratio between the metal concentra tions in the metal buffer and test solutions, positive and negative peaks c an be recorded with respect to the baseline.