Multi-element surveys

Trends in element analysis are multi-element (survey) analysis, lower concentration levels, micro/local element analysis and speciation (coupling with chromatography). An overview of the determination of elements in polymeric materials is available [7], Reviews on sample preparation for trace analysis are given in refs [8-10]. Quality assurance of analytical data in routine elemental analysis has been discussed [11], Organic analysis is obviously much more requested in relation to polymer/additive matrices than elemental analysis. 

Applications Real applications of spark-source MS started on an empirical basis before fundamental insights were available. SSMS is now considered obsolete in many areas, but various unique applications for a variety of biological substances and metals are reported. Usually, each application requires specific sample preparation, sparking procedure and ion detection. SSMS is now used only in a few laboratories worldwide. Spark-source mass spectrometry is still attractive for certain applications (e.g. in the microelectronics industry). This is especially so when a multi-element survey analysis is required, for which the accuracy of the technique is sufficient (generally 15-30% with calibration or within an order of magnitude without). SSMS is considered to be a... 

Steinnes, E., Rambaek, J. P., and Hansson, J. E. (1992). Large scale multi-element survey of atmospheric deposition using naturally growing moss as biomonitor. Chemosphere 25, 735—752. 

C. A. Weeks, M. Croasdale, M. A. Osborne, L. Hewitt, P. F. Miller, P. Robb, M. J. Baxter, P. D. Warriss, T. G. Knowles, Multi-element survey of wild edible fungi and blackberries in the UK, Food Addit. Contam., 23 (2006), 140D147. 

Micro-PIXE with a 20 micron beam spot has proved to be a versatile tool for investigations of water and electrical trees, as well as a variety of other samples. This system is simple to operate and does not require complex target preparation, so that multi-element surveys of a variety of samples can be rapidly performed. 

VG Isotopes Ltd., is another leading manufacturer of ICP-MS equipment. The special features of their VG Plasmaquad PQ2 includes a multi-channel analyser which ensures rapid data acquisition over the whole mass range. The multi-channel analyser facilities include 4096 channels, 300 m facility for spectral analysis, user-definable number of measurements per peak in peak jumping mode, and the ability to monitor data as they are acquired. A multi-channel analyser is imperative for acquiring short-lived signals from accessories such as flow injection, electrothermal vaporisation, laser ablation, and so on, or for fast multi-element survey scans (typically 1 minute). 

Surface analysis by non-resonant (NR-) laser-SNMS [3.102-3.106] has been used to improve ionization efficiency while retaining the advantages of probing the neutral component. In NR-laser-SNMS, an intense laser beam is used to ionize, non-selec-tively, all atoms and molecules within the volume intersected by the laser beam (Eig. 3.40b). With sufficient laser power density it is possible to saturate the ionization process. Eor NR-laser-SNMS adequate power densities are typically achieved in a small volume only at the focus of the laser beam. This limits sensitivity and leads to problems with quantification, because of the differences between the effective ionization volumes of different elements. The non-resonant post-ionization technique provides rapid, multi-element, and molecular survey measurements with significantly improved ionization efficiency over SIMS, although it still suffers from isoba-ric interferences. 

The actual analysis of the samples started with a qualitative survey to identify the principal metals present. ICP-AES was selected as being most suitable for this because it provided a permanent record, a multi-element analysis, and good sensitivity. Solutions of the shellfish tissue were prepared for analysis by wet oxidation, and the sediments were digested with 40% v/v... 

For many decades, spark source mass spectrometry (SSMS) was the method of choice for survey analyses of quite different types of geological materials, especially for the sensitive multi-element... 

Some refractory elements cannot be determined by ET-AAS at the levels usually present in waters. That is the case with M. El Himri et al. [28] developed a fast and accurate procedure, without any prior treatment, to analyze tap and mineral waters from Spain and Morocco for this highly toxic element. ICP-MS was employed. The analytical isotope selected was 238U, with Rh as internal standard. An LoD of 2ngl 1 was obtained. The estimated repeatability was 3 percent at the concentration level of 73 ng l-1. The method was validated by comparison with a radiochemical procedure devised for natural samples and by analysis of a Certified Reference Material (CRM). Multi-element capabilities of ICP-AES have also been employed for surveys of trace elements. Al-Saleh and Al-Doush [29] reported the concentrations of dissolved Be, Cd, Cr, Cu, Fe, Mg, Mn, Hg, Ni, Se, Sr, V, and Zn in 21 samples of retail bottled waters from Riyadh, Saudi Arabia. It was found that Cd, Fe, Hg, Ni, and Zn were present at concentrations higher than the limits recommended by the EU and World Health Organization (WHO) guidelines. 

Historically, analysis for selenium has been difficult, partly because environmental concentrations are naturally low. Indeed, selenium analysis still remains problematic for many laboratories at concentrations below 0.01 mg a relatively high concentration in many environments (Steinhoff et al., 1999). Hence, selenium has often been omitted from multi-element geochemical surveys despite its importance (Darnley et al., 1995). Analytical methods with limits of detection of <0.01 mgL include colorimetry, total reflectance-XRF, HG-AFS, gas chromatography... 

Table 11.1 provides examples of recent multi-element vacuum dust surveys in urban environments around the world, not including industrial or geochemical hotspots. The data in Table 11.1 are summarized using geometric means or medians... 

The above can be illustrated by data taken from several multi-element air pollution biomonitor surveys carried out at IRI The air pollution surveys commonly include a number of soil-associated elements (e.g. Al, Fe, Sc, Cr, Th) and several rare earth elements (Kuik et al., 1993a,b). In the Factor Analysis interpretation of the data on all selected 20 elements, the soil indicator elements serve to extract a soil-factor (De Bruin and Wolterbeek, 1984), based on which, for all individual elements, site-specific soil-associated fractions of the total concentrations can be calculated (Kuik et al., 1993a,b). 

The laser beam efficiently vaporizes conductors, insulators, and semiconducting materials with a minimum of matrix effects. Laser sampling ICP-MS has also been applied successfully as a semi-quantitative survey tool for a rapid multi-element analysis of geological samples. The samples are pulverized to assure homogeneity. Some paraffin wax is mixed with the sample. The mixture is then placed in an aluminium cup and pressed into a wafer. 

Note The analytical problems of inorganic MS often require only certain selected isotopes or narrow m/z ranges to be measured. Multicollector systems, for example, are adjusted to simultaneously detect a few isotopes for the purpose of accurate isotope ratio determinations or to quantify a low-abundant isotope together with an isotopic standard for internal reference. Thus, the data is more often presented in tabular form or in plots of concentration versus variables such as depth of invasion, age of samples, or location on a surface. Mass spectra covering a wider range are only acquired for survey multi-element detection. 

The target population for a survey is that set of elements about which the data will be used to make inferences. The target population for the national radon survey will be all occupied residential housing units in the United States which are used as primary residences. This will include both single and multi-family housing units. The survey will not include schools, workplaces, group quarters (dormitories, institutions, rooming houses, etc.), seasonal units, or unoccupied units. 

Organometallic chemistry is currently reviewed element by element in at least three independent publications. The first in-depth review appeared as a single volume in 1965 entitled Annual Survey of Organometallic Chemistry (Bl). This covered the literature of the previous year. After three annual issues the publication became multi-authored and was incorporated into Organometallic Chemistry Reviews as Series B (as distinct from Series A, subject reviews). In January 1973, the surveys became part of the Journal of Organometallic Chemistry. At the time of writing, coverage is complete for all elements to the end of 1973, except Si (1970) Be, Ca, Sr, Ba, Si, Pb (1971) Si (1972) and Li, Na, K, Ge, Pb, As, Sb, Bi (1973). 

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