A study of iodine loss during the preparation and analysis of samples using 131I tracer and neutron activation analysis

Abstract

The recoveries of various species of iodine, such as I 2 , IO 3 2 and organic iodine, in the procedures of acid digestion, ashing, freeze-drying, evaporation drying and neutron irradiation were studied using 131 I tracer and instrumental neutron activation analysis. The recoveries of iodine were over 99% after drying at room temperature and 60-80 °C for various iodine species in all kinds of media. The organic iodine in various media, I 2 and IO 3 2 in biological materials and IO 3 2 in alkaline solution were not lost after freeze-drying, whereas I 2 in aqueous solution and IO 3 2 in acidic and neutral solution were significantly lost. The recoveries of iodine were different under various acid digestion conditions. Under the optimum conditions, more than 96% of iodine remained in the digestion solution. With ashing, the recovery of iodine was less than 2%. Addition of alkali to the samples can significantly improve the iodine recovery, but the ashing is incomplete in this case. Only 90% of iodine was recovered using alkali ashing at 650 °C. Neutron irradiation did not cause any loss of iodine.

Determination of 129I in seawater and some environmental materials by neutron activation analysis

“…Under optimum conditions of 650 °C for ashing temperature and a 0.2-0.3 weight ratio of KOH to sample, 70-85% of iodine can be recovered in the leachate. 26 In this work, a recovery as high as 98% was observed for seaweed samples; it probably resulted from the high iodine concentration (more than 100 mg g 21 ) in seaweed. The total recovery of iodine, including extraction, ranges from 60 to 65% for grass samples and 85 to 97.5% for seaweed samples.…”

“…The analytical methods for grass and seawater have been described in detail elsewhere. 25,26 For soil samples, 0.5 ml of separated iodine solution (see section 1.2.2) was taken and sealed in a half-dram polyvial. The iodine content was determined by radiochemical NAA.…”

“…iodide in basic solution is quite stable on evaporation under low temperature. 26 We studied the loss of iodine in seawater under evaporation using 131 I tracer. The results show that with pH > 9, 94-98% of iodine (as I 2 and IO 3 2 ) was retained in the solution after evaporation on a hotplate with boiling and with more than 20-fold concentration of seawater.…”

Retrospective measurements of airborne 129Iodine in Austria

“…The concentration of 129 I was derived from the isotopic ratio using the concentration of stable iodine and chemical yield for iodine separation determined from ICP-MS. Only the chemical yield of the first step, namely leaching of air filters by reflux heating in alkaline medium could not be controlled. According to Hou et al, loss of iodine at pH 9e10 and 60e80 C is negligible (Hou et al, 1998).…”

Effects of drying on the nutrient content and physico-chemical and sensory characteristics of the edible kelp Saccharina latissima

“…In kelp species, the iodine accumulates naturally in the extracellular matrix in the form of iodide (I -) which readily scavenges a variety of reactive oxygen species (ROS) from both aqueous and gaseous oxidants (Küpper et al 2008). A study from Hou et al (1998) reported reduced recovery of iodide in aqueous solutions following freezedrying (30 to 40%) compared to air-drying (100%) although a similar effect of freeze-drying on the recovery of iodide directly from seaweed material was not observed. However, the chemical species of iodine are known to differ among seaweeds and no mention is made of the species used in this study.…”