Determination of Trace Iodine in Soils, Sediments and Rocks by ICP-MS after Pressurized Acid Digestion-Hydroxylamine Hydrochloride Reduction

Abstract

BACKGROUND Iodine is an active element with many valences. It is easy to transform each other between valence states and its chemical properties are unstable. In terms of determination of trace iodine in soil, sediment and rock samples by inductively coupled plasma-mass spectrometry (ICP-MS), sample pretreatment and result stability are the main problems. OBJECTIVES To obtain stable results, low blank, a short analysis period and complete extraction. METHODS The sample was digested by phosphoric acid-perchloric acid under high-pressure sealed conditions. The decomposition efficiency of the sample was improved and the volatilization loss of iodine was avoided. The stability of iodine was improved by adding 0.5mL 20g/L hydroxylamine hydrochloride solution to reduce iodine to I-. The iodine was kept in an oven at 10℃ for at least 20 minutes, and the memory effect during ICP-MS analysis was reduced by using dilute ammonia water as the medium. RESULTS The relative standard deviations of the method were 4.88%-9.19%, the relative errors were -6.90%-8.33%, the recoveries were 92.5%-109.6% and the detection limit (3s) was 0.012μg/g. CONCLUSIONS The data obtained by this method are in good agreement with those obtained by the semi-melting method. It solves the problems of long analysis process, high blank, incomplete extraction of rock samples and various extraction devices. It can be used as a supplement to the determination of trace iodine in soil, sediment and rock, and is suitable for batch sample analysis.

Keywords

• soils
• sediments
• rocks
• pressurized acid digestion
• hydroxylamine hydrochloride
• inductively coupled plasma-mass spectrometry
• iodine