Application of plasma spectrometry (ICP-AES, ICP-MS) to the analysis of sediments: an evaluation study using standard reference materials

Increased interest in the geochemistry of sedimentary samples by geologists and environmental scientists has led to the release of a range of new sedimentary standard reference materials (SSRM). Many of these standards, however, remain relatively poorly characterized when compared with established igneous rock reference materials. Lack of characterization is a result of a number of factors, including: (a) sediments vary considerably in composition and most differ greatly from igneous rocks; (b) few geochemical laboratories specialize in sediment analysis, and therefore few have instruments which have been calibrated for this type of material; (c) many trace elements occur at low levels in sediments, and consequently are difficult to determine by most routine analytical techniques; (d) many SSRMs have been released relatively recently and have not yet been characterized by a sufficiently large number of laboratories and/or techniques. We have used a combination of inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and ICP-mass spectrometry (ICP-MS) to study the compositions of a range of generally available SSRMs: Geological Survey of Japan (JSd-1, JSd-3 stream sediments; JCh-1 chert; JLk-1 lake sediment; JSl-1, JSl-2 slates; JDo-1 dolomite; JLs-1 limestone), National Institute of Standards and Technology, U.S.A. (1c argillaceous limestone; 88b dolomitic limestone), National Research Council of Canada (BCSS-1, MESS-1, PACS-1 marine sediments), United States Geological Survey (MAG-1 marine mud; SCo-1 Cody shale; SGR-1 Green River shale) and University of Liege (AWI-1 shale; CCH-1 limestone; DWA-1 dolomite; PRI-1 psammite; SBo-1 schist). Samples were prepared in triplicate by three independent techniques: (1) fusion with lithium metaborate and digestion in dilute HNO3; (2) digested in sealed microwave vessels using HF, HNO3, and HClO4 acids, evaporation, and dissolution in dilute HNO3; and (3) grinding with agate beads in a Na4P2O7 suspending agent. The first two preparations were analyzed by solution nebulization ICP-AES and ICP-MS; samples prepared by the third method were analyzed by slurry nebulization ICP-MS only. The advantages and disadvantages of ICP-AES and ICP-MS for major and trace element analysis will be discussed, and procedures will be suggested for the routine determination of a wide range of elements in sedimentary materials by plasma spectrometry.