Total reflection X-ray fluorescence medical applications: Elemental analysis of human urine

Abstract

The main goal of this research is to define reference values of elemental concentration in human urine. The second topic is to develop a fast analytical method for multielemental analysis of human urine by means of a low-power benchtop total reflection X-ray fluorescence system. For this purpose a set of certified human urine and real samples was employed. All of the parameters affecting sample preparation and measurement conditions were carefully evaluated, and finally, the procedure for optimal urine preparation and optimal measurement conditions is defined. The accuracy and precision of the measurements were verified using an internal standardization approach for quantification. As results, the reference values of concentration of several elements (K, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb and Sr) were defined on the basis of the analysis of 100 urine samples. Donors were presumably healthy volunteers from the Świętokrzyskie Province in Poland: 62 women and 38 men. Because of the strong asymmetry of elemental concentration distributions, the median and the 1st and 3rd quartiles reflect features of the distributions better than the mean value and standard deviation (which are proper for symmetric distributions). Finally, the 1st and 3rd quartiles were accepted as the initial and final values of the concentration reference range. For measurements, in which the concentration is below the detection limit of the method used (i.e. for Cr, Mn, Cu, Se), the well-known random-left censoring approach was applied for the statistical analysis of the results.