Flow Injection System for Chloride Determination with Multidetection Based on Potentiometric and Spectrophotometric Measurements

Original Paper

Abstract

The present paper describes the feasibility of a flow injection system with multidetection based on potentiometric and spectrophotometric measurements for chloride determination. Chloride determination by potentiometry was accomplished by using two electrodes of Ag/AgCl where the first one act as the indicator in the first zone sample and the second one act as reference electrode, resulting a an positive signal. After zone sample reaches the second electrode the first electrode will be the reference electrode, generating a negative signal. For the spectrophotometric determination, it was used the conventional reaction between Hg(SCN)₂ and chloride with further displacement of SCN^- and formation of complex with Fe (III) detected at 480 nm. The linear work range was limited by the spectrophotometric detector and resulted in 10 to 500 mg L^-1. The method was applied to determine chloride in samples of parenteral solutions and the results obtained, with both detectors, were in agreement at 95 % confidence level (paired t-test). The precision evaluated as repeatability (n=20) for samples analyzed showed relative standard deviations (RSD) smaller than 3.5% for multidetection employed. The FIA with multidetection results is better reliable, since it consists of doing two determinations of the same analyte with different detectors. It is similar to what is done with two independent determination of the analyte.