RESUMO
Objective To verify the determination of iodine in foodstuff by dry ashing As3+-Ce4+catalytic speetrophotometry.Methods The mixture of foodstuff powder and the solution of K2CO3,ZnSO4,KClO3 and NaCl was heated and dried at 105℃ for 3 hours,then heated by a adjustable electric heater for around 0.5 hour,transferred into muffle fumace to eremated at 600℃ for 4 hours.The dissolved ash was measured by As3+-Ce4+catalytic speetrophotometry.The linear range of the calibration and sensitivity were tested;The precision and accuracy for three kinds of iodine in samples of difierent pumpkins were tested:The iodine contents of standard urine samples and the American standard materials were tested as well.Results This testing covers iodine ranged from 4.4 ng to 250 ng.The relevance coefficient of standard curve was from-0.9997 to-0.9993.The pumpkin iodine contents detected were 45.8,145.0,195.6 μg/kg,with constant variables of 4.3%,3.0%and 3.9%respectively.The recovery was 96.8%,97.8%and 97.6%for three kinds of iodine in samples[(47.2±2.6),(71.9 4-3.3),(95.9±2.4)μg/kg].The relative error was-6.5%when the American standard materials were assessed.The relative error were 11.0%.10.7%and 10.7%when the standard urine samples of three kinds were tested.Conclusion This method,easy to be pefformed with better precision and accuracy,is suitable to measure food iodine as well as total iodine in urine.
