Analysis on the feasibility in determination of salt iodine content of Sichuan with oxidation-reduction titration / 中国地方病学杂志

ABSTRACT

Objective To investigate the influential factors and the control measures thereof iodine salt detection with oxidation-reduction titration method so as to improve the detection quality.Methods 122 samples were obtained randomly from four counties(districts)of Sichuan Province to determine iodine ions forms.In center for diseases control and prevention(CDC)laboratories at the provincial and county levels,iodine contents in the samples were determined with oxidation-reduction titration and the results were compared between laboratories.The provineial lahoratory also employed bromine water oxidation for method comparison.Also the volume fractions of chlorine available were determined in sodium hypochlorite storage in open or sealed status and of different storage periods of 1,2,4,7,14,30 and 60 days.Results The iodine transformed from 103- to I-during the shipment and storage;The iodine contents in the 122 salt samples determined by the laboratories at the provincial and county levels were respectively(32.40±8.44),(31.10±8.34)mg/kg with a result discrepancy of 1.33 mg/kg.Of all the absolute discrepancy values,18.8%(23/122)were lower than or equal to 1 mg/kg;23.0%(28/122)were equal to or higher than 3 mg/kg;23.0%(28/122)were lower than or equal to 5 mg/kg;26.2%(32/122)were lower than or equal to 10 mg/kg;9.0%(11/122)were higher than 10 mg/kg.After the botdes were opened and stood for 60 days,the available chlorine content in the sodium hypochlorite decreased by 43.6%and 32.5%respectively in open and sealed status,Iodine contents were respectively(32.60±8.44),(32.50±8.18)mg/kg(n=114)with the oxidationreduction titration method and bromine water oxidation method,and no significant difierence was found between the results of the two methods(t=0.282,P＞0.05).Conclusions Potassium iodate in salt in Sichuan is Dmne to transform into potassium iodide during shipping,so when determining salt iodine with the oxidation-reduction titration method,the content and the amount of chlorine available in the sodium hypochlorite differ a lot and are difficult to control.Therefore.bromine water oxidation titration is recommended.