Mixture design for developing an eco-friendly sample preparation procedure in a closed-block digester for analysis of...

This study presents a green and efficient digestion method for determining Ba, Ca, Mg, Mn, Ni, P, S, Sr, V, and Zn in tropical fruit pulps using ICP OES. A constrained-mixture design was used to optimize a diluted acid digestion in a closed-block digester, maximizing the efficiency of organic matter decomposition (%EOMD). Optimal conditions included 4.0 mL of 2.0 mol L^-1 HNO₃ and 2.0 mL of 30 % H₂O₂ for 1.30 g of wet mass (0.20 g dry mass), ensuring low acid consumption, minimal residual carbon, and high %EOMD. Accuracy was confirmed through analysis of certified reference material (NCS DC 73351 tea) and spike-recovery tests, showing satisfactory agreement. The method's greenness and practicality were evaluated using AGREE (score: 0.54) and AGREEprep (score: 0.38). Applied to 41 pulp samples, the method enabled multivariate analysis that revealed distinct clusters based on mineral profiles. This approach offers a sustainable and reliable alternative for trace element determination in fruits.