title: Ammonium persulfate: a new and safe method for measuring urinary iodine by ammonium persulfate oxidation.
abstract: The chloric acid method is most commonly used to obtain accurate and reproducible measurements of iodine and removes interfering substances. Unfortunately, chloric acid is a potential hazard requiring an explosion proof hood among other precautions. We have developed a simple, convenient, and economic method for measuring urinary iodine using 1 mol/L ammonium persulfate, a non-explosive, non-hazardous chemical, as the oxidizing reagent. The oxidation procedure can be completed in 30 minutes at a temperature of 91-95 degrees C. The iodine in the urine is then measured by a modification of the traditional colorimetric method of Sandell-Kolthoff. 110 urine samples collected from a mixed population of healthy males and females, ranging in age from 6 to 79 years and living in the United States were analyzed for iodine content by two methods: the proposed ammonium persulfate method and the chloric acid method. The ammonium persulfate method has an intra assay CV of 9.1% at 0.42 +/- 0.04 micromol/L (mean +/- SD), 7.8% at 1.46 +/- 0.11 micromol/L and 4.0% at 3.54 +/- 0.14 micromol/L. The inter assay CV is 10.2% at 0.46 +/- 0.05 micromol/L and 7.9% at 3.27 +/- 0.26 micromol/L. Recovery of iodine added to urine in vitro was 107%, 94% and 97% for 0.42 micromol/L, 0.77 micromol/L and 3.64 micromol/L, respectively. The lower limit of detectability was 0.0034 microgI. Values for iodine in 110 urines measured by the reference chloric acid method ranged from 0.06 to 8.03 micromol/L and by the ammonium persulfate method from 0.05 to 7.4 micromol/L. The persulfate method (y) correlated extremely closely with the reference chloric acid method (x) by the Pearson correlation (y = 0.923x + 0.810 micromol/L, and r = 0.994, Syx = 1.841). In conclusion a new, safe, simple method for measuring urinary iodine is described which uses ammonium persulfate as the oxidizing agent for the removal of interfering substances.
authors.affiliation: Division of Endocrinology, University of Massachusetts Medical Center, Worcester 01655, USA.
authors.forename: S
authors.initials: S
authors.lastname: Pino
authors.forename: S L
authors.initials: SL
authors.lastname: Fang
authors.forename: L E
authors.initials: LE
authors.lastname: Braverman
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000645:Ammonium Sulfate; D001322:Autoanalysis; D002648:Child; D002704:Chlorates; D005260:Female; D006801:Humans; D007202:Indicators and Reagents; D007455:Iodine / Q000652:urine*; D008297:Male; D008875:Middle Aged; D016877:Oxidants; D010084:Oxidation-Reduction; D012449:Safety; D012680:Sensitivity and Specificity
chemical_list: D002704:Chlorates; D007202:Indicators and Reagents; D016877:Oxidants; C031276:ammonium peroxydisulfate; D007455:Iodine; D000645:Ammonium Sulfate; C022842:chloric acid