Validación y estimación de la incertidumbre de metales pesados (Ba, V, Cu y Zn) en suelos, mediante espectrofotometría de absorción atómica, en el laboratorio ambiental LABSU

Abstract

The method for determining Barium, Vanadium, Copper, and Zinc by atomic absorption spectrophotometry in soil was validated at the LABSU Environmental Laboratory. This is located in Francisco de Orellana. The standardized method for soil analysis was selected based on the procedures described in METHOD 7000B: FLAME ATOMIC ABSORPTION SPECTROPHOTOMETRY, EPA METHOD 3050B: ACID DIGESTION OF SEDIMENTS, SLUDGES, AND SOILS, and APHA METHOD 3111: STANDARD METHODS FOR THE EXAMINATION OF WATER AND WASTEWATER. The validation objectives were then established, and the experimental design for each analyte was developed, including method optimization, validation data collection, ANOVA, uncertainty calculation, and method declaration; following the internal procedures of the INEN ISO 17025:2018 standard and related methodologies. Through statistical analysis, the method met key parameters such as a repeatability and reproducibility coefficient of variation (SR) < 10%, accuracy (recovery) between 80% and 120% at all levels, and uncertainty (U) ≤ 32% of the lowest range with a confidence interval (k=2). The assessment concluded that the critical parameters related to method response linearity were within acceptable limits, with %CV values of 8% for Barium, 9% for Vanadium, 8% for Copper, and 8% for Zinc. The recovery percentages were 85.14% for Barium, 85.13% for Vanadium, 115.39% for Copper, and 115.74% for Zinc. Meanwhile, the method uncertainty (U) was 27% for Barium, 28% for Vanadium, 29% for Copper, and 22% for Zinc. A linear response with r ≥ 0.995 was obtained for the calibration curves of the analyzed metals, demonstrating that the method is suitable for its intended application, providing reliable and reproducible results in accordance with the laboratory’s established guidelines. It is recommended to conduct interlaboratory tests for each parameter, refine calibration curves, and verify potential interferences in the analysis.