Sample Preparation Techniques for Geological Samples

Single particles are analyzed directly by being fixed on such tape or embedded in epoxy, and mass spectrometric measurements are carried out on cut and polished cross sections. 

A thin metallic layer (e.g., Au) deposited on geological sample is helpful before direct mass spectrometric measurements because in SIMS charging effects occur due to the sputtering process of non-conducting samples. 

Another analytical procedure for sample preparation including analyte separation and enrichment is the coprecipitation of the trace elements to be determined. The co-precipitation behaviour of Ti, Mo, Sn and Sb under two different fluoride forming conditions (at 70 °C in an ultrasonic bath and at 245 °C using a Teflon bomb) has been studied to improve the accuracy of the trace analysis of these elements in Ca-Al-Mg fluorides, by ICP-MS.14 The applicability of this analytical method (including isotope dilution technique) was demonstrated for four carbonaceous chondrites and silicate reference materials of basalt or andesite.14 

An analytical procedure for the determination of about 20 trace elements in coal samples after microwave digestion is described by Wang et al.15 It was found that high temperature digestion with HN03 alone (250 °C, 7.5 MPa) led to an extensive decomposition of the organic matrix and clay in coal, whereby solid carbon remained in the final solution after evaporation. Most of the trace elements were quantitatively dissolved in three standard coals. A lost of Hg was observed during the evaporation step. 

In addition, selected rare elements, such as precious metals, were extracted from matrix elements and preconcentrated to avoid isobaric interferences with polyatomic ions as demonstrated for platinum determination in the presence of a relatively high concentration of Hf, resulting in isobaric interferences at m/z = 194, 195 and 196 due to HfO+ diatomic ion formation.17 An improved method for extracting marine sediment fractions and its application for Sr and Nd isotopic analysis is described by Bayon et al.ls 

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