A comparative study on alkaline ashing method and chloric acid digestion method for determination of human milk iodine / 中国地方病学杂志

ABSTRACT

Objective Take alkaline ashing method as golden standard to explore the accuracy of chloric acid digestion method in determination of human milk iodine. Methods Sixty one breast milk samples collected in Hexi district of Tianjin was measured by the method for determination of iodine in foodstuff by As3+-Ce4+ catalytic spectrophotometry (referred to as the alkaline ashing method) published in 2008 and the method for determination of iodine in urine by As3+-Ce4+ catalytic spectrophotometry(referred to as acid digestion) published in 1999, respectively. were highly correlated(r = 0.960, t = 26.3, P < 0.01), and the regression equation was (Y) = - 28.1 + 0.808X, in which X was independent variable, that is the results of alkaline ashing method; (Y) was dependent variable, that is the estimated data of chloric acid digestion method. The average difference of the results measured by the two methods was 68.3 μg/L, and the results from chloric acid digestion was 38.9% which lower than that of alkaline samples were diluted by 3,4 and 5-fold and then digested by chloric acid, the liquid clarification rates were 80.3% ashing and chloric acid digestion method were, respectively, 165.4, 110.0 μg/L. Conclusions Compared with alkaline ashing method, the results determined by chloric acid digestion method are significantly lower. It is suggested that there are systemic errors in chloric acid digestion method, which means that alkaline ashing method can not be replaced by the chloric acid digestion method.