Analytical Methods for Determining Heavy Metals, Trace Elements and Rare Earth Elements in Environmental and Biological Samples: Instrumentation, Validation, and Interpretation from 2000–2026

Determination of heavy metals, trace elements and rare earth elements (REEs) in sediments, soils, plants, molluscs, fish, water, aerosols and related environmental matrices is a foundation for pollution assessment, food safety, biomonitoring, geochemical tracing and human-health risk evaluation. From 2000 to 2026, the analytical field has moved from single-element determinations by flame atomic absorption spectrometry toward high-throughput multi-element methods, field screening, element speciation and data-driven interpretation. This review synthesizes journal papers, standard methods and reference-material guidance on sample preparation and elemental measurement in environmental and biological samples. The methods reviewed include flame and graphite furnace atomic absorption spectrometry, hydride-generation and cold-vapour atomic spectrometry, inductively coupled plasma optical emission spectrometry, inductively coupled plasma mass spectrometry, tandem and high-resolution ICP-MS, X-ray fluorescence including portable and total-reflection systems, instrumental neutron activation analysis, laser-induced breakdown spectroscopy, anodic stripping voltammetry, direct mercury analysis and chromatographic speciation methods coupled to element-selective detection. For each technique, the paper compares suitable matrices, equipment, detection capability, advantages, disadvantages, quality-control requirements, certified reference materials, and operational constraints. The review emphasizes that validated concentration data require matrix-matched certified reference materials, blanks, duplicates, spike recovery, calibration verification, detection-limit reporting and uncertainty evaluation. Finally, the paper summarizes how elemental concentration data can be transformed into pollution indices, sediment-quality guideline quotients, bioaccumulation and translocation factors, source-apportionment models, REE-normalized patterns, geospatial maps, ecological risk and non-carcinogenic or carcinogenic human-health risk metrics. A tiered method-selection and interpretation framework is proposed for environmental laboratories and researchers.