Spectrophotometric determination of iodate in iodised salt by flow injection analysis

A simple and sensitive flow injection (FI) method for the determination of iodate is proposed. The method is based on the reaction of iodate with hydroxylamine in acidic solution. Sulfanilamide is diazotised by the nascent nitrite and the diazonium ion produced is then coupled with N-(1-naphthyl)ethyenediamine in hydrochloric acid medium to form an azo dye which is measured spectrophotometrically. The calibration graph for iodate is linear in the range of 0.1–30 mg L−1 with a correlation coefficient of 0.9992. The limit of detection and relative standard deviation are 0.02 mg L−1 and 1.2% (5 mg L−1, n = 8). The method has been applied to the determination of iodate in table salts and accuracy was assessed through recovery experiments and independent analysis by a conventional titrimetric method.