Читать книгу X-Ray Fluorescence in Biological Sciences - Группа авторов - Страница 81

In any analytical technique, validation of the method is the most important quality control issue. Accurate and precise results depend on the careful construction of the method or analytical technique which produces them. A calibration curve was constructed using three lab‐synthesized secondary standards of arsenic in varying concentrations (5.8, 9.5, and 14.8 ppm) prepared from commercially available 1000 ppm As standard (Mark, Germany). The secondary standards were prepared by doping 2 g of cellulose with different amount of As [7]. The accurate concentrations of the element in the standards was obtained by the source excited by EDXRF. Figure 6.3 shows the calibration plot of As reflecting a good regression value. A certified reference material (CRM) Orchard Leaf (NIST 1571) obtained from the US‐based National Institute of Standards & Technology, was prepared and analyzed under same condition as the real samples and used to check the accuracy and precision of the analytical method [8]. The calculated values of relative error (%) and variation (%) as shown in Table 6.1. was found in good agreement with the certified values and within an error margin of 10%, thus confirming the method is quite fit for purpose.