Pressurised Extraction Using Dilute Ammonia: A Simple Method for Determination of Iodine in Soil, Sediment and Biological Samples by Inductively Coupled Plasma‐Mass Spectrometry

Abstract

A simple sample treatment method for the accurate and precise determination of iodine in soil, sediment and biological samples by inductively coupled plasma‐mass spectrometry (ICP‐MS) is described. Iodine in samples was extracted in screw top PTFE‐lined stainless steel bombs using a 10% v/v ammonia solution at 185 C for 18 hours (overnight), after which the extract was introduced into the ICP‐MS for direct measurement. 126Te was employed as the internal standard to compensate for matrix effects and instrument drift. The limit of detection (LOD, three times the standard deviation of the procedural blank solution, expressed as the concentration in the sample solution) was 0.003 ng ml‐‐1. The limit of quantitation (LOQ, ten times the standard deviation of the procedural blank solution, expressed as the concentration in the solid samples, dilution factor DF = 100) was 0.01 μg g‐‐1 (dry mass). The accuracy and precision of the method were demonstrated by analysing different Chinese geological certified reference materials (soils, stream sediments and a hair sample). The measured concentrations were in a good agreement with the certified values indicating that bias in the method was not significant. The precision (n = 10) for different concentrations ranged from 1.82% to 4.32% RSD. Comparison of the ammonia extraction procedure with a “sintering” method indicated that there was no significant difference in results obtained with the two methods for geological soil and stream sediment samples. However, for biological samples, such as hair, kelp, tea etc., the results obtained by the sintering method were far below those of the ammonia extraction method. The ammonia extraction has advantages, as it is simpler than the “sintering” method, and has a lower procedural blank, better detection limits and reproducibility. Due to the simplicity of the method, a high rate of sample throughput is possible.

Natural iodine in a clay formation: Implications for iodine fate in geological disposals

“…This discrepancy between INAA and RNAA could either be explained by the fact that the INAA measurement was performed on another batch or by a lower sensitivity than RNAA (Ebihara et al, 1997). This preliminary test made it possible to show that the ammonia alkali digestion method proposed by Bing et al (2004) is not adapted to clay rock samples, although it gives valuable results for the certified standard. Differences in iodine* environment (type of organic matter or mineral) between the certified standard and the clay rock sample are certainly responsible for the observed discrepancy.…”

“…The sample is mixed with flux (sodium carbonate and zinc oxide), sintered at 650°C for 40 minutes in a muffle furnace and then dissolved in hot water. However, these vaporization techniques are not easy to perform in the laboratory and the use of a large amount of flux, cation-exchange resin and matrix separation step leads to a high procedural blank, with a consequent deterioration in the detection limit (Michel and Villemant, 2003;Bing et al, 2004).…”

“…Recently, Bing et al (2004) have developed a simple method. Iodine* is extracted in screw top PTFE-lined stainless steel bombs using a 10% v/v ammonia solution at 185°C.…”

“…According to the author, this method is suitable for determination of iodine* in soil, sediment and biological samples. Given the apparent disagreement of results when using different techniques, we decided to apply and compare four different techniques in order to obtain the total iodine* concentration: overnight extraction by nitric acid digestion at 90°C in closed PFA (perfluoroalkoxy) vessels or ammonia method (Bing et al, 2004) followed by Inductively…”

Ultra-trace determination of iodine in sediments and biological material using UV photochemical generation-inductively coupled plasma mass spectrometry

“…A variety of sample preparation techniques has been proposed for the determination of iodine by ICP-MS: simple dilution or solubilization in an alkaline medium such as ammonia [20,21], NaOH [22] or tetramethylammonium hydroxide (TMAH) [22,23], mixed acid wet digestion [24][25][26][27], fusion [28,29], and combustion [18,19,25,30,31].…”