The automatic determination of iodide or iodate in solution by catalytic spectrophotometry, with particular reference to river water

Abstract

A catalytic procedure, in which a Technicon AutoAnalyzer(I) is used, for determining iodide or iodate (50 µg l^–1) added to river water (during river-flow gauging operations by the dilution method) is described. The maximum error of the analytical procedure, as determined by replicate analysis of six sets of eleven samples, is ± 0·36 per cent. in the range 20–100 µg l^–1. The setting up of the procedure is described in detail, according to Mark's (1973) recommendations. The shape of the most appropriate calibration graph is considered. Also, the effects of changes in temperature, reaction period and spectrophotometric variables are discussed. This information could be used directly in the development of methods for determining iodine in other types of sample, e.g., protein-bound iodine in blood or urine and iodate or iodide in sea water, etc. Further, it could also be used in developing other automatic procedures that rely upon catalytic reactions that follow a pseudo-first-order behaviour.