Validation and Comparison of Two Calibration Methods for the Measurement of Stable Iodine in the Urinary Matrix by ICP-MS: Standard Addition vs. External Calibration

Background: Inthe context of a nuclear reactor accident, thyroid is the main target organ ofradioactive iodines. To avoid as much as possible thyroid disorders or evencancer development, it is recommended to administer a single dose of potassiumiodide to people at risk of exposure. Nevertheless, the Fukushima Dai-ichidisaster has pointed out many questions about the conditions of stable iodineprophylaxis implementation highlighting the need for reflection furtherrevision of the actual “iodine doctrine”. Therefore, providing useful data is requirednotably through the implementation of animal experiments to strengthen currentknowledge and to edit new recommendations. Methods: Urinary iodineconstitutes a verygood indicator to investigate the function of thyroid, its interpretationdemands reliable analyses. Priorto perform animal experiments, two calibration methods were designed by our laband compared together (standard addition and external calibration) to assessthe urinary concentration of stable iodine in urine by ICP-MS. They werevalidated based on several key parameters especially linearity, accuracy andlimits of detection (LOD) and quantification (LOQ). Results: Theresults were nicely satisfying. Indeed, both calibration methods have indicatedvery good coefficients of correlations, accuracies with lowexpanded relative uncertainties were obtained. The estimated LOD in the samplefor standard addition method and external calibration were fully acceptable,0.39 μg·L-1 and 0.35 μg·L-1,respectively. All performance criteria have been thus fulfilled successfully. The established methodswere proven to be accurate, robust and sensitive. Once validated, bothcalibration methods were applied to raturine samples and the results of z-score and Wilcoxon W test concluded that there were nostatistically significant differences between both methods.