FSCN 4613 Lecture Notes - Lecture 2: Ammonium Sulfate, Creatinine, Arsenite
5 Apr 2020
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Urine samples must first be digested with a strong acid to remove interfering substances. Will use ammonium persulfate to oxidize material in urine, with heating. Urinary iodine measured by reduction of ceric ions. Measure iodine using reaction developed by sandell & kolthoff. Reduction of ceric ammonium sulfate by arsenite in the presence of iodine (as catalyst) Ceric ammonium sulfate is yellow, cerous ammonium sulfate is colorless. The more iodine present, the less color in the sample. The longer the reaction runs, the greater the formation of the cerous ion. Must therefore time the reaction to be same for each tube. The greater the concentration of urinary iodine, the greater the rate of reduction in absorbance. Must measure all tubes at the same time interval after addition of the ceric ammonium sulfate, since absorbance changes continually over time. Creatinine excreted at approximately constant amount for each person. Can be used to account for differences in dilution of urinary constituents.
