Trace element determination in seawater by ICP-SFMS coupled with a microflow nebulization/desolvation system.

Abstract

Direct and simultaneous determination of Al, Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Sb, U, V and Zn in diluted (1:10 v:v) seawater from the Antarctic Ocean and the Venice Lagoon at the ng mL(-1) and pg mL(-1) level has been performed by using an inductively coupled plasma sector field mass spectrometer (ICP-SFMS). Samples were analysed by using a PFA microflow nebulizer coupled with a desolvation system or a PFA microflow nebulizer coupled with a Teflon spray chamber, respectively. Measurements were carried out at low (LR, m/Delta m=300), medium (MR, m/Delta m=3,000) and high (HR, m/Delta m=7,500) resolutions depending on the studied isotope. To avoid contamination, sample pre-treatment was carried out in a clean laboratory equipped with a Class 100 vertical laminar flow hood. Concentration ranges (minimum-maximum in ng mL(-1)) found in the Antarctic seawater samples (in depth profiles) were: Ag 0.0004-0.0018, As 0.69-1.32, Cd 0.031-0.096, Co 0.018-0.065, Cr 0.18-0.46, Cu 0.04-1.58, Fe 0.13-1.63, Mn 0.02-0.12, Mo 5.97-12.46, Pb 0.007-0.074, Sb 0.033-0.088, U 0.5-1.9, V 0.6-2.5 and Zn 0.16-0.80. Concentration ranges (min-max in ng mL(-1)) found in the Venice Lagoon water samples (temporal profile from a benthic chamber experiment) were: Al 0.24-0.61, Ag 0.007-0.031, As 1.42-2.27, Cd 0.050-0.182, Co 0.440-1.461, Cr 0.15-0.34, Cu 0.81-2.46, Fe 0.25-1.66, Mn 11.6-31.7, Mo 6.50-10.6, Pb 0.047-0.225, Sb 0.240-0.492, U 1.7-3.3, V 1.3-2.8 and Zn 5.20-21.5. The detection limits range between 0.06 pg mL(-1) for Ag and U to 15 pg mL(-1) for Fe. In order to check the accuracy of the analytical procedure, measurements of the trace elements in a certified reference material (coastal Atlantic seawater, CASS-4-NRCC) were compared with the certified values. In addition, the results from the Antarctic and Venice Lagoon samples were compared with those obtained by using different analytical techniques.