Methods development for sampling and analysis of chlorine, chlorine dioxide, bromine, and iodine. Research report for iodine.
A sampling and analytical method for the determination of iodine (7553562) in air was developed and tested. Treated charcoal tubes were exposed at iodine concentrations ranging from 0.074 to 0.211 parts per million (ppm) as determined by a calibrated monitor. Each individual tube was exposed for 15 minutes at a sampling rate of about 1 liter per minute. The temperature of the test atmosphere was 26 degrees-C; its relative humidity was about 50 percent. After sampling, each tube was capped and stored overnight. The collected iodine was desorbed as iodide with a 10 millimolar solution of sodium-carbonate. The tubes were then extracted, and the extracts were analyzed by an optimized ion chromatographic procedure. The overall average recovery was 90.8 percent when uncorrected for the desorption efficiency and 94.3 percent when corrected. The precision of the results at all test concentrations was found to be homogenous. The values of the relative standard deviation were pooled to yield a value of 6.2 percent. The relative standard deviation for the total procedure, including pump error, was calculated to be 8.5 percent. The developed method was expected to yield an iodine concentration that was within 25 percent of the true result 95 percent of the time. Substances which could be separated by this ion chromatographic method included fluoride, chloride, bromide, iodate, nitrate, phosphate, and sulfate anions from the analyte iodide ion. The authors conclude that the advantages to the method include the small, portable sampling device, the avoidance of potential sources of interference, and analysis of the samples by a quick instrumental method. One disadvantage is that the precision of the method is limited by the reproducibility of the pressure drop across the tubes which affects the flow rate resulting in imprecise sample volumes. However, the method is valid for determining iodine in air.
NIOSH, U.S. Department of Health and Human Services, Cincinnati, Ohio