Selective solvent bar micro-extraction as a single-step approach for the measurement of Cu fractions in seawater

Hollow fibre-supported liquid membrane was used for Cu fractionation in marine waters, using di-2-pyridylketone benzoylhydrazone (dPKBH) as a carrier due to its capacity to transport dissolved inorganic Cu at natural seawater pH. Optimized conditions were dPKBH (0.5 mmol L^-1), HNO₃ (0.5 mol L^-1) as acceptor agent, extraction time of 120 min and stirring speed of 800 rpm. Additionally, the selectivity of the method for the extraction of the inorganic Cu fraction was validated by comparing the experimental results with theoretical data, and a mathematical model was obtained for estimation of Cu linked to dissolved organic matter. The method was applied for the measurement of Cu fractions in real seawater samples. Results were successfully compared with the reference material BCR 403 and recovery analysis in waters from the Gulf of Cádiz, showing that it could be used as a simple approach for the study of different Cu fractions in marine waters. Graphical abstract.