ABSTRACT
Objective To set up an uncertainty assessment method for urinary iodine measurement by As3+-Ce4+ catalytic spectrophotometry,in order to assess the accuracy of this method and find out the major influence factors.Methods A mathematical model was established based on the determination method to evaluate the uncertainty component of various factors such as potassium iodate benchmark,standard curve calibration,glass equipment,balance weighing,temperature control instrument,etc.,and the uncertainty of the test results of urinary iodine standard substances was analyzed.Results The iodine content of the urinary iodine standard material GBW09108i was (72.6 ± 3.7) μg/L,and the relative expansion uncertainty was 5.10％,within the tolerance range allowed by the reference material certificate (10.0％).Among them,the calibration of the standard curve,the uncertainty of the volume of the glass equipment and related consumables had a great influence on the extended uncertainty.Conclusion The method can be used to assess the uncertainty for determination of iodine in urine by As3+-Ce4+ catalytic spectrophotometry.
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.