Determination of Iodine in Soil and Sediment by Ion Chromatography after Closed Melting with Aqueous Ammonia

After the soil and sediment samples were collected, dried, crushed and screened, 0.100 0 g of the samples were taken and placed into an anti-corrosion melting tank, and 8 mL of 10% (volume fraction) aqueous ammonia solution (flux) was added. Under closed conditions, the mixture was heated and melted at 190℃ for 12 h. After 0.1 mL of 15 g·L^-1 ascorbic acid solution was added, the mixture was diluted to 15 mL with water, and centrifuged for 5 min. An aliquot (10 mL) of the supernatant was taken and filtered through a 0.22 μm filter membrane, and the filtrate was injected into the ion chromatograph. The mixture of 3.2 mmol·L^-1 sodium carbonate solution and 1.0 mmol·L^-1 sodium bicarbonate solution was used for eluting on the Metrosep A Supp 5-150/4.0 anion chromatographic column, and amperometric detector was used for detection. As found by results that the mass concentrations of iodine were linearly related with corresponding peak areas within 50 μg·L^-1, with detection limit (3.143s) of 0.15 μg·g^-1. Tests for precision and accuracy were carried out on standard substances and actual samples, and the determined values were within the uncertainty ranges of the certified values, with the recoveries in the range of 95.0%-96.0% and RSDs (n=6) of the determined values less than 10%. The above method was compared with the industrial standard method of DZ/T 0279.23-2016, giving the determined values of the two methods basically the same, and RSDs (n=6) of the determined values of the above method were lower than those given by the industrial standard method.