Flow injection spectrophotometric method for chloride determination in natural waters using Hg(SCN)2 immobilized in epoxy resin

A flow injection (FI) spectrophotometric method was proposed for the determination of chloride ion in natural waters. The determination of chloride was carried out by reaction with Hg(SCN)2 immobilized in an epoxy resin bead in a solid-phase reactor (SPR) and the thiocyanate ions released were determined spectrophotometrically at 480 nm after complexing reaction with Fe(III). The analytical curve for chloride was linear in the concentration range from 5.6 × 10−5 to 2.2 × 10−4 mol l−1 with a detection limit of 1.4 × 10−5 mol l−1. The relative standard deviation (R.S.D.) was 2.2% for a solution containing 2.2 × 10−4 mol l−1 (n = 10). The simple manifold allows a routine analytical frequency of 100 determinations per hour. The main advantage of the developed method is the 400% reduction of the Hg waste solution generated when compared to conventional methods for chloride determination based on the same spectrophotometric reaction.