Plasma spectrometry in the earth sciences: techniques, applications and future trends (original) (raw)
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Geoanalysis using plasma spectrochemistry ? milestones and future prospects
Analytical and Bioanalytical Chemistry, 1996
Highlights of plasma spectrochemistry in geoanalysis are reviewed. The techniques are evaluated in terms of recent instrumental developments, calibration strategies, spectral and matrix interferences and analytical performance. While acid decomposition results in solutions containing low salt contents, this decomposition strategy is inappropriate for numerous sample types due to poor recoveries. On the other hand, alkali fusions result in total decomposition, but solutions containing high salt contents constrain the accuracy due to interference effects in the inductively coupled plasma (ICP), the sample introduction system, and in the quadrupole mass spectrometer interface. Therefore, practical limits of determination are evaluated in terms of salt tolerances. It is concluded that ICP-atomic emission spectrometry (AES) is employed mainly for the accurate determination of the major and minor elements and the more abundant trace elements. On the other hand, ICP-mass spectrometry (MS) is used mainly for the determination of trace elements and together with the possibility of obtaining some isotopic information, it profoundly enhances the capability for solving geochemical problems. Several methods of direct solid sample introduction are described. These include direct current (DC) arc emission spectroscopy (DC-AES), slurry nebulization (SN), spark ablation (SA), laser ablation (LA) and glow discharges (GD). These devices allow direct solid analysis of bulk samples, single minerals and inclusions.
Spectrochimica Acta Part B: Atomic Spectroscopy, 1998
The analytical performance of a high transmission interface (S mode), inductively coupled plasma-quadrupole mass spectrometer (the VGE Plasma Quad 3) was evaluated for multitrace element analysis of geological and environmental materials. The sensitivity, limits of detection (LODs), effect of Ca and Na and other major elements on mass response, background, percentage 156 CeO + / 140 Ce + , 70 Ce ++ / 140 Ce + , and long-and short-term variations were compared with those obtained with the conventional mode (normal mode). Normal mode sensitivities varied from 20 MCPS ppm −1 (millions of counts per second per ppm) for 9 Be + , 70-80 MCPS ppm −1 for 59 Co + , 90 for 115 In + and 40-50 MCPS ppm −1 for the heavy masses. S mode sensitivities were 180 MCPS ppm −1 for 59 Co + , 350-380 for 115 In + and 140 Ce + , 300 MCPS ppm −1 for 208 Pb + , and 150 MCPS ppm −1 for 232 Th + and 238 U + , i.e. enhancements amounting to 7. Three j normal and S mode LODs are mainly in the 1-2 and 0.1 ppt range, respectively. S mode LODs are enhanced relative to the normal mode, for masses Ͼ80 amu, by factors ranging from about 10 to 50. S mode LODs are depressed relative to normal mode LODs for masses Ͻ50 amu by a factor of 10, and the extent of depression is related linearly to mass. In the high-and mid-mass ranges, backgrounds were about 10. They were not affected by sample composition: at 8 amu the S mode background for real samples amounted to about 20, whereas at 220 amu it amounted to four counts. S and normal mode percentage 156 CeO + / 140 Ce ++ and percentage Ce ++ /Ce + ratios were about 1.5%, and temporal variations were insignificant. The percentage RSDs of normal and S mode Sr + , Ag + and Pb + isotope ratios were about 0.1%, with the exception of S mode 208 Pb + and 208 Pb + / 206 Pb + ratios in the presence of NaCl, which were degraded by a factor of about 2. Normal and S mode long-term variations for continuous aspiration of 0.1% NaCl for periods of up to 13 h were mass dependent, varying from 2.5-4% for 7 Li + and 9 Be + to about 2% for the mid-mass range, increasing slightly to about 3% for high masses. Most of this variation occurred during the first 100-150 min of the analysis during cone priming. With compensation, normal and S mode long-term percentage RSDs and drift were reduced to 1-2%. These variations indicate that extended periods of S mode analysis can be conducted without periodic recalibration. A calibration procedure, based on spiked HNO 3 , was validated by analysing spiked NaCl solutions, standard water and geological standard reference material (SRM) solutions with internal standardization using conventional solution delivery and flow injection. The agreement of the S mode data and the certified and literature values for ultratrace elements, including ppt levels of rare earth elements in the water standards, was satisfactory. An important conclusion is that ion sampling effects in the S mode are minimal and that the enhanced ion transmission interface is not only beneficial for microanalysis using laser ablation, but for geological and environmental
Fresenius Journal of Analytical Chemistry, 1999
During the past decade, inductively coupled plasma mass spectrometry (ICPMS) has evolved from a delicate research tool, intended for the well-trained scientist only, into a more robust and well-established analytical technique for trace and ultra-trace element determination, with a few thousand of instruments used worldwide. Despite this immense success, it should be realized that in its 'standard configuration' -i.e. equipped with a pneumatic nebulizer for sample introduction and with a quadrupole filter -ICPMS also shows a number of important limitations and disadvantages: (i) the occurrence of spectral interferences may hamper accurate trace element determination, (ii) solid samples have to be taken into solution prior to analysis and (iii) no information on the 'chemical form' in which an element appears can be obtained. Self-evidently, efforts have been and still are made to overcome the aforementioned limitations to the largest possible extent. The application of a double focusing sector field mass spectrometer in ICPMS instrumentation offers a higher mass resolution, such that spectral overlap can be avoided to an important extent. Additionally, in a sector field instrument, photons are efficiently eliminated from the ion beam, resulting in very low background intensities, making it also very well-suited for extreme trace analysis. Also the combination of the ICP as an ion source and a quadrupole filter operated in a socalled 'alternate' stability region, an ion trap or a Fourier transform ion cyclotron resonance mass spectrometer allows high(er) mass resolution to be obtained. With modern quadrupole-based instruments, important types of spectral interferences can be avoided by working under 'cool plasma' conditions or by applying a collision cell. The use of electrothermal vaporization (ETV) or especially laser ablation (LA) for sample introduction permits direct analysis of solid samples with sufficient accuracy
Geostandards and Geoanalytical Research, 2000
At that time no inductively coupled plasma-mass spectrometers (ICP-MS) were in operation in China, and thus analytical data were obtained by inductively coupled plasma-atomic emission spectrometry (ICP-AES), X-ray fluorescence (XRF), instrumental neutron ac tivation analy sis (INA A) and atomic absorption spectrometry (AAS), as well as other techniques. Chinese laboratories analysed essentially all twenty six samples with few contributions from international laboratories. After 1985, a few laboratories analysed some of these reference materials for a few elements using INAA, XRF and ICP-MS (Zhang et al.