A versatile and greener multicommuted flow-based system for exploiting relatively slow chemical reactions

Abstract

A multi-commuted flow system was designed for implementing spectrophotometric methods based on relatively slow chemical reaction. It comprised six-way solenoid valves with reaction coils coupled to each port, which provided long sample zone residence times in the analytical path yet maintaining the sampling rate. Potentialities of the system were demonstrated by selecting the reaction of iodate (IO3−) with p-aminophenol (PAP) in acidic medium, which yielded a purple compound with absorption maximum at 540nm. Although more than 40min were needed for reaching chemical equilibrium, sampling rate of the proposed flow system was 70h−1. The innovation was applied to iodate determination in table-salts, and favorable features such as a linear response from 2.28×10−5 to 3.65×10−4mol L−1 iodate, a detection limit (99.7% confidence level) of 8.2×10−6mol L−1, and a coefficient of variation (n=20; IO3−=1.37×10−4mol L−1) of 0.42% were attained. Furthermore, pronounced lessening in reagent consumption and effluent generation, estimated at 1.05mg PAP and 0.7mL of waste per determination. The results agreed with those obtained by a titrimetric procedure at 95% confidence level.