Validation of the ASTM E1898-21 Method with Estimation of Analytical Uncertainty for the Determination of Silver by FAAS

Silver is one of the most important precious metals in mining and metallurgy. Thus, the methods used to determine its concentration are critical. The objective of this research work was to validate and estimate the expanded uncertainty of the ASTM-E1898-21 method for silver determination by flame atomic absorption spectroscopy. The methodology used for the validation and estimation of the expanded uncertainty is recommended by international regulations. The validation results showed precision values under repeatability conditions with variations in the range of 1.67–2.04%, whereas the accuracy showed values of 0.0131–0.1445 for the bias evaluated through Z-score and recovery percentages from 100.7 to 104.8. The validation of the analytical method was confirmed using a certified reference material (CDN-GS-1Z), and precision values under repeatability conditions of 1.677 for the percentage of variation and recovery percentages of 100.65 were obtained. Further, the evaluation of the relative combined uncertainty showed values from 0.0046 to 0.1166 for the different sources of uncertainties evaluated. On the other hand, the expanded uncertainty obtained was 2.572 mg/L of silver with a reliability factor of 95% (k = 2).