Determination of trace elements in filtered suspended marine particulate material by sector field HR-ICP-MS

Quantification of particulate (w0.45 mm) and dissolved (v0.45 mm) trace elements in seawater is imperative for understanding geochemical cycling in the marine environment. Suspended particulate trace element concentrations are typically v10% of total element concentrations in seawater. To overcome analytical difficulties associated with low analyte concentrations, it is common to filter large volumes (tens to thousands of litres) of seawater. We report a novel method for the rapid quantification of Al (324 ppb), P (159 ppb), V (2.02 ppb), Cr (2.85 ppb), Mn (22.3 ppb), Fe (304 ppb), Co (0.129 ppb), Ni (0.817 ppb), Cu (1.68 ppb), Zn (3.25 ppb), Mo (0.264 ppb), Ag (0.079 ppb), Cd (0.029 ppb), Ba (3.54 ppb), Pb (1.13 ppb) and U (0.053 ppb) in digest solutions of suspended matter, filtered from 0.2 to 5.0 L of seawater. Filter digest solutions, consisting of a complex matrix of filter residue, sea salt, dissolved solids and strong acids, are analyzed on the ELEMENT, a high resolution, inductively coupled plasma mass spectrometer (Finnigan-MAT, Bremen, Germany). High sensitivity (w1610 counts s ppb In; with shielded torch) combined with low flow rates (mFlow nebulizer, Elemental Scientific) provide excellent absolute detection limits (0.4 to 720 pg depending on the element). A resolution of 300 (low resolution) is appropriate for interference-free high mass analytes of interest (Ag, Cd, Pb, Ba and U), whereas 4300 (medium resolution) is sufficient to resolve all plasma-, waterand matrix-based polyatomic interferences on low mass analytes (Al, P and first row transition metals). The precision of the method is better than ¡4% for most analytes. Accuracy could not be determined conventionally using a certified reference material (not available), but was estimated from spiked samples to be v¡4% when calculated using a standard additions curve and v¡10% for most elements if using an external standard curve.