A Greener Acid-free Microwave-Assisted Digestion Method for Multielement Analysis of Fish Tissues by ICP–MS

Abstract Trace element monitoring in fish tissues requires reliable and sustainable sample preparation methods, particularly for complex biological matrices. In this study, an acid-free microwave-assisted digestion (AFMAD) method based exclusively on H2O2 was developed and optimized for multielement determination in fish tissues by ICP–MS. A central composite design coupled with response surface methodology was employed to evaluate the influence of H2O2 concentration, ramp time, and digestion temperature on matrix decomposition efficiency using 100 mg of dry fish tissue subsamples throughout the method development. The optimized conditions consisted of 30% (v/v)H2O2, 8 min ramp time, a 20 min hold time and 240 °C, resulting in residual carbon contents below 20%, which indicates efficient oxidation of the organic matrix using H2O2 in the absence of HNO3. The analytical performance of the proposed method was evaluated using cod muscle certified reference material (BCR-422), providing recoveries ranging from 76 to 101% for Fe, Cu, Zn, Mn, As, and Cd. Excellent linearity was obtained for all analytes (R2 > 0.990) within the 0–50 μg L–1 range. Limits of detection ranged from 0.0004 to 0.04 μg g–1, demonstrating suitable sensitivity for trace elemental analysis in fish matrices. The applicability of the method was demonstrated through the analysis of five commercial fish species collected in the Mariana-MG region. Concentrations of toxic elements were found in Megaleporinus conirostris (Cd, 0.003 mg kg–1) and Cichla ocellaris (As, 0.07 mg kg–1) and remained below the maximum limits established by Brazilian legislation. The proposed AFMAD method demonstrated satisfactory analytical performance for complex fish matrices while eliminating the use of concentrated mineral acids, reducing hazardous reagent consumption, and improving the sustainability characteristics of sample preparation procedures for elemental analysis.