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ICPMS Analysis
The element iodine normally exists as iodide in nature, however other common forms include iodate and molecular iodine.
Total iodine, iodine in any and all forms, can be determined using ICPMS. WCAS now has validated methods for total iodine in blood and urine at ug/L levels using ICPMS. While the sensitivity of ICPMS for iodine is excellent, the background, its tendency to adsorb onto glass, and its chemistry all have to be controlled for successful
quantitative analysis in complex matrices.
Iodide, in the presence of acid, will form molecular iodine. Molecular iodine will cause of memory affects and background problems due to its adsorption onto glass. Consequently, total iodine by ICPMS is best performed in dilute base such as 0.1% ammonium hydroxide. Dilutions and digestions must also be conducted in base such as ammonium hydroxide or tetramethylammonium hydroxide (TMAH).
Ion Chromatography Analysis
Ionic forms of iodine, such as iodide or iodate, may be determined using Ion Chromatography (IC). Detection limits using IC with supressed conductivity detection are generally in the 0.1-1 ug/mL range.
The chromatogram below shows a combination of IC and ICPMS with detection limits of less than 1 ug/L. In this case the analysis was conducted on a Dionex AS16 column with 35 mm sodium hydroxide. The eluent is taken through a Dionex anion suppressor then into the ICPMS.
IC-ICPMS
10 ug/L Standard of Iodate and Iodide
Organic Forms of Iodine
Organic forms of iodine are also common (iodoform, iodomethane, etc.). Volatile and semivolatile forms of organic iodine may be determined by GC and GCMS.
These are just a few of the ways that iodine and various compounds containing iodine can be determined. There are many more options that have not been discussed.
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