Determination of iodate in waters by cuvetteless UV–vis micro-spectrophotometry after liquid-phase microextraction

The combination of liquid-phase microextraction and microvolume UV–vis spectrophotometry has been applied to the determination of iodate in natural water samples. The method is based on the reduction of iodate into vapor iodine and extraction of this volatile onto a single drop of N,N′-dimethylformamide.The following derivatization reaction was employed:IO3− + 5I− + 6H+ → 3I2 + 3H2OOptimum conditions employed for iodate determination were as follows: 2.5 μL N,N′-dimethylformamide exposed to the headspace of a 10 mL acidic (HCl 0.2 mol L−1) aqueous solution stirred at 1400 rpm for 7 min after addition of 1 mL of KI 10−3 mol L−1 for in situ iodine generation. The limit of detection was determined as 1.1 μg L−1. The repeatability, expressed as relative standard deviation, was 4.2% (n = 6). A large preconcentration factor (i.e. 396) was obtained in only 7 min.