Assessment of uncertainty in determination of water iodide level by As3+-Ce4+ catalytic spectrophotometry / 中华地方病学杂志

ABSTRACT

Objective We set up an uncertainty assessment method for determination of iodides in water by As3+-Ce4+ catalytic spectrophotometry, in order to assess the accuracy of the method and the major influencing factors, and to build up an equation to assess the uncertainty in the mobility of working curve and an uncertainty assessment method for pipettors.Methods According to Methods for Water Iodine Detection Suitable for Iodine Deficiency and Iodine Excess Areas, the uncertainty items of the two standard materials (GBW09114c and GBW09113c) in different concentrations, such as repeatability of measurement, the mobility of working curve, the uncertainty of standard solution and sample solution, etc, were analyzed.Results The contents of iodide in GBW09114c and GBW09113c were (61.3 ± 1.4) and (8.1 ± 0.3)μg/L;relative expanded uncertainty RU1 and RU2 were 2.25％ and 3.46％, both of them were in the range of acceptable deviation in the standard material certification (10.0％ and 14.8％).Major influencing factors were repeatability of measurement, the uncertainty of standard solution (including the uncertainty of potassium iodide reference reagent and glass equipment), and the uncertainty of sample solution (including the uncertainty of pipettors).A more adaptable equation for the mobility of working curve had been proposed;the factors involved in environment temperature and operation repeatability were used as the items of the pipettors' uncertainty.Conclusion This method can be used to assess the uncertainty in determination of water iodides by As3+-Ce4+ catalytic spectrophotometry.