Headspace single-drop microextraction and fibre optics-based cuvetteless micro-spectrophotometry for the determination of chloride involving oxidation with permanganate

Headspace single-drop microextraction has been investigated for the determination of chloride in conjunction with fibre optic-based cuvetteless micro-spectrophotometry which accommodates sample volume of 1 μL placed between the two ends of optical fibres. Method has been evolved for the determination of 0.025–4 mg L−1 of chloride involving its oxidation with permanganate in sulphuric acid medium, and reaction of chlorine with 2 μL drop of starch-iodide reagent suspended at the tip of microsyringe needle in the headspace of the reaction mixture. The limit of detection was found to be 2.8 μg L−1 of chloride which was better than obtained by existing methods. The method was highly selective and a number of ions which interfered severely in other methods did not affect the results. The method has been used to analyze water samples, inorganic compounds and cement when the overall recovery of chloride was 94.9% with a relative standard deviation of 3.9%.