Assessment of a screening method for metals in seawater based on the non-selective reagent 4-(2-pyridylazo)resorcinol (PAR) Original Research Article

A screening method for the simultaneous spectroscopic determination of heavy metals in seawater matrices has been developed and evaluated. A pH 9.0 buffer solution containing the non-selective reagent 4-(2-pyridylazo)resorcinol (PAR) is added to the samples, and spectra in the wavelength range 260–600 nm are recorded. Calibration is based on partial least squares regression (PLS1). The method has been applied for screening of polluted seawater samples with total heavy metal concentrations in the range 2–20 μmol l−1, containing 1–4 of the heavy metals Cd2+, Cu2+, Pb2+ and Zn2+. The method also allows the simultaneous determination of Ca2+ and Mg2+, naturally present in seawater or present at elevated levels through pollution, in the concentration range 0.75–13.0 mmol l−1 Ca2+ and 0.78–21.1 mmol l−1 Mg2+. The maximum concentration of these latter ions correspond to those typically found in ocean water samples. RMSEP values were in the order 0.4–0.9 μmol l−1 for the heavy metals, 1.2 mmol l−1 for Ca2+ and 1.6 mmol l−1 for Mg2+. The influence of pH variations has also been investigated. Neither sample dilution nor addition of masking agents is required.