A review of sequential extraction methods for fractionation analysis of toxic metals in solid environmental matrices

Abstract

This review provides a thorough examination of SEMs for the fractionation analysis of toxic metals within solid environmental matrices. It offers an overview of these techniques' principles and applications for determining the chemical fractions of toxic metals associated with such matrices. The review assesses and contrasts the strengths and weaknesses of SEMs for chemical fractionation analysis. Additionally, it highlights the specifications data offered by SEMs. The discussion encompasses the metal fractions targeted by each SEMs and their relevance regarding metal mobility, bioavailability, and potential risk evaluation. Applications in contaminated sites, environmental monitoring, and remedial measures are also addressed. The review emphasizes the importance of standardization and quality assurance when analyzing toxic metals. It presents current guidelines, protocols, and inter-laboratory studies that aim to ensure the dependability and comparable nature of outcomes. Changes in pH, redox states, and organic content influence metal mobility in solid matrices. Lower pH levels enhance metal solubility, particularly in exchangeable and carbonate-bound fractions, while higher pH levels promote metal precipitation and reducing mobility. SEMs such as the Tessier and BCR methods consistently achieve >85% metal recovery, with standard deviations and confidence intervals ensuring the reliability of metal fraction assessments in environmental samples. Metal fractions in solid matrices typically follow the order: oxidizable > residual > reducible > exchangeable. Ultimately, its objective is to impart a comprehensive understanding of SEMs, appraise their efficacy, showcase their applications, and steer future practices in the realm of metals fractionation analysis in solid environmental matrices.