Determination of total and labile fraction of metals in seawater using solid phase extraction and inductively coupled plasma atomic emission spectrometry (ICP-AES)

A rapid and simple method is described for the preconcentration and discrimination between the organic fraction and the labile fraction of the metals Mn, Cd, Cu, Z, V, Ni, Pb, and Fe from seawater using 8- hydroxyquinoline, which forms neutral complexes with these metals, followed by adsorption on C18 chemically bonded silica gel. The sample flow rate through the C18 column was about 4 ml min(-1). The metal ions adsorbed on the C18 column were stripped using 10 ml of nitric acid ( 2M) and the volume of seawater sample was about 500 ml ( preconcentration factor, similar to 50). Trace metal ions and the major elements ( Ca, Na, Mg, K) were analysed in the samples using inductively coupled plasma atomic emission spectrometry ( ICP- AES). The results of fractionation showed that Cd, Pb, Mn and V were mainly in the labile fraction, while the other studied metals were partially present in the organic fraction. Also the results showed excellent reproducibility, and the accuracy of the method was demonstrated by measurement of total metal concentrations from runs of certified reference materials, SLEW- 3, CASS- 3, NASS 3, which have different ionic strengths.