Electromembrane Extraction for Metal and Metalloid Analysis: Species-Dependent Transport, Coordinated Method Design, and Evidence-Based Translation

Electromembrane extraction (EME) applies an electric field and a supported liquid membrane to transfer charged analytes into a small acceptor phase. For metal and metalloid analysis, the field contribution is coupled to aqueous speciation, interfacial reactions, membrane composition, and acceptor-side trapping. This critical narrative review evaluates direct analytical EME evidence and distinguishes it from removal, recovery, and materials studies. The analysis links species-dependent transport and coordinated method design to the strength of evidence for different measurement claims. Available studies primarily support multication determination and Cr(III)/Cr(VI) differentiation in water, together with targeted As(V), As(III), Hg(II), and total-mercury workflows. Broader applicability to food and biological matrices remains insufficiently established. Reported enrichment or selective response alone does not demonstrate preservation of native species, matrix robustness, or universal multielement performance. Reliable translation therefore requires claim-matched validation in authentic matrices, control of species conversion, analyte-specific performance assessment, mass-balance verification, reproducible operating windows, and transparent reporting. This framework delineates the demonstrated capabilities and current evidence boundaries of analytical EME while identifying priorities for more reproducible and transferable separation and sample-preparation workflows.