Fractional Distributions of Major-to-Ultratrace Elements in Coastal Seawater and Their Partitionings in Laboratory-Made Salts as Investigated by Inductively Coupled Plasma Atomic Emission Spectrometry and Inductively Coupled Plasma Mass Spectrometry with Aid of Membrane- and Ultra-filtration Techniques

Abstract

The coastal seawater sample was filtered with a membrane filter (pore size 0.45 μm), and the filtrate was further filtered with an ultrafiltration filter (molecular weight permeation limit of 10000 Da). Then, major-to-ultratrace elements in the particles which remained on the membrane filter, the membrane-filtered seawater, and the ultrafiltered seawater were determined by ICP-AES (inductively coupled plasma atomic emission spectrometry) and ICP-MS (inductively coupled plasma mass spectrometry). From these analytical results, the fractional distributions of each element in the particle, large molecule and small molecule fractions of seawater were estimated, where the distributions of the elements in the large molecule fraction were obtained as the differences between the elemental concentrations in membrane-filtered and ultrafiltered seawaters. Furthermore, laboratory-made salts (Salts I—III) were prepared from original, membrane-filtered, and ultrafiltered seawaters. The concentrations of major-to-ultratrace elements in laboratory-made salts were also determined by ICP-AES and ICP-MS. It was found that alkali metals, alkaline earth metals, oxoanion-forming elements (V, Mo, W, U) and Cd were mostly contained in the small molecule fraction of seawater, and ca. 95—100% of them in salt, except for V, originated from those in the small molecule fraction. More than 50% of Al, Mn, Fe, Co, Ga, Y, rare earth elements (REEs) and Pb were contained as the particle constituents in seawater, but their intakes into salt were less than 50%. In addition, the fractional distributions of the following elements in the large molecule fraction of seawater were: Al 10%, Mn 4%, Fe 2%, Cu 23%, Zn 7%, Y 5%, REEs 3—15%, and Pb 30%. On the other hand, the intake factors of these elements in salt from the large molecule fraction were: Al 40%, Mn 5%, Fe 28%, Cu 20%, Zn 30%, Y 7%, REEs 5—30%, and Pb 55%. The results obtained in the present experiment suggest that the distributions of the elements in natural salt greatly depend on the chemical forms in seawater.

Atomic Spectrometry Update. Environmental analysis

“…The chemical stability of large organic molecule metal complexes dissolved in natural water were investigated by on-line size exclusion chromatography ICP-MS. Acidi®cation of the samples with HNO 3 was found to have a marked effect on the size exclusion chromatograms. The partitioning of major to ultra-trace elements in coastal sea-water sequentially ®ltered to 0.45 mg and subsequently ultra-®ltered to a molecular weight permeation limit of 10 000 Da was investigated by analysing the particulates and ®ltrates obtained at each stage using a combination of ICP-AES and ICP-MS. 103 A detailed account of the fractionation of a wide range of metals is given. Hg is well known for its ability to `plate-out' onto the walls of sample storage containers.…”