Trace-matrix separation

Sample preparation, which is generally minimized for solid samples, can be a time consuming and labour intensive process, especially if trace matrix separation is required. Due to the huge variety of different matrices, of more or less complex matrix composition, many different decomposition principles have been developed. 

Chemical separation of matrix and preconcentration of analytes is used to avoid matrix effects, clogging effects on the cones and disturbing interferences of analyte ions with polyatomic ions of matrix elements and plasma gases. A trace/matrix separation method is required for ultratrace analysis. 

For some applications, precipitation and co-precipitation, which is often incomplete, is utilized. As an example, for trace matrix separation the procedure for plutonium determination by ICP-SFMS in urine after trace matrix separation is summarized in Figure 6.29.86 87 The limit of detection for 239 Pu ultratrace determination in one litre of urine based on enrichment factor of 100 using the DIHEN in ICP-SFMS was 1.02- 10 18g mF1.86... 

Figure 6.29 Procedure for Pu determination in urine after trace matrix separation. (M. Zoriy,...

An interesting approach is the application of multiple ion collector mass spectrometry (MC-TIMS and MC-ICP-MS) for the determination of Cd and T1 in high purity zinc metal after trace matrix separation by the certification of reference materials from the Bureau Communie de Reference (BCR).29 Accurate and precise element concentrations in high purity zinc metal have been obtained with both mass spectrometric techniques via precise isotope ratio measurements using the isotope dilution strategy the analytical data. 

Similar to the analytical procedure for trace analysis in high purity GaAs wafers after matrix separation, discussed previously,52 the volatilization of Ga and As has been performed via their chlorides in a stream of aqua regia vapours (at 210 °C) using nitrogen as the carrier gas for trace/matrix separation.58 The recoveries of Cr, Mn, Fe, Ni, Co, Cu, Zn, Ag, Cd, Ba and Pb determined after a nearly quantitative volatilization of matrix elements (99.8 %) were found to be between 94 and 101 % (except for Ag and Cr with 80 %). The concentrations of impurities measured by ICP-DRC-MS (Elan 6100 DRC, PerkinElmer Sciex) after matrix separation were compared with ICP-SFMS (Element 2, Thermo Fisher Scientific) and total reflection X-ray fluorescence analysis (TXRF Phillips). The limits of detection obtained for trace elements in GaAs were in the low ngg-1 range and below.58... 

As the most important inorganic mass spectrometric technique, ICP-MS is also employed for the precise and accurate isotope ratio measurements of a multitude of elements (such as Li, B, S, Fe, Sr, Pb, U, Pu) in environmental samples (see Chapter 8).9,88-90 Isotope ratio measurements of environmental samples require special careful sample preparation techniques including trace/matrix separation and enrichment procedures if the analytes are at the trace and ultratrace level. As an example, the schematic diagrams of the separation and enrichment procedures for the precise isotope analysis of Pu, U and Sr in water samples from the Sea of Galilee using double-focusing... 

Environmental control in respect of determining concentrations and isotope ratios, e.g. of U, Pu and other actinides, is also required in routine measurements near to nuclear power plants, uranium enrichment facilities or nuclear waste recycling companies. Groundwater samples are analyzed after dilution directly by ICP-MS for soils a digestion step before mass spectrometric measurement is necessary. If isobaric interferences are observed a trace matrix separation and/or a careful analyte separation (e.g. of U and Pu) is recommended. 

Methodological Developments and Applications of ICP-MS for Determination of Long-lived Radionuclides Including Trace/Matrix Separation... 

Long-lived radionuclides occur at extremely low concentrations, especially in environmental samples, therefore several authors have proposed matrix separation and enrichment of the analytes before analysis.21,24,26,3 39 Radiochemical methods often require very careful and time consuming separation and enrichment processes and measurement procedures of a-, (3- and -emitting radioactive species at the trace and ultratrace level using conventional radioanalytical techniques 40-43 Trace/matrix separation, which is performed offline or online in order to avoid possible isobaric interferences, matrix effects and to reduce the detection limits for the determination of long-lived radionuclides, is also advantageous before ICP-MS measurements as the most widely applied mass spectrometric technique. 

Figure 6.29 Procedure for Pu determination in urine after trace matrix separation. (M. Zoriy, C. Pickhardt, P. Ostapczuk, R. Hille, ]. 5. Becker, Int. j. Mass Spectrom 232, 217 (2004). Reproduced by permission of Elsevier.)...

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