Multielement techniques

Although ICP-AES is a multielement technique, its inferior detection limits relative to GFAAS would necessitate the processing of large volumes of seawater, improvements in the preconcentration procedures in use thus far, or new, alternative preconcentration procedures such as carrier precipitation (see below). 

The instrumental revolution has also lead to a data affluence previously unrealized. Multielement techniques capable of simul-... 

Spark source mass spectrometry (SSMS) is also a multielement technique. Conventionally the data obtained are semiquantitative, and the results have an uncertainty of 50% or less. If the stable isotope dilution technique is performed, the SSMS can be 3%. This latter technique was used for lead, cadmium, and zinc as noted in the results tabulations. NAA and SSMS complement each other quite well, and those elements for which one technique has poor sensitivity can usually be measured by the other. 

ICP-MS is a multielement technique that is suitable for trace analysis it offers a long linear range and low background for most elements. ICP-MS is a technique where the ions produced in inductively coupled plasma are separated in a mass analyzer and detected. The sample solution is fed into a nebulizer by a peristaltic pump. The nebulizer converts the liquid sample into a fine aerosol that is transported into the plasma by an Ar gas flow. In the plasma the sample is evaporated, dissociated, atomized, and ionized to varying extents. The positive ions and molecular ions produced are extracted into the mass analyzer. Detailed descriptions of the ICP-MS technique can be found in a number of textbooks.13,14... 

The multielement function of the plasma-based techniques has been a source of challenges in the AAS field. This has resulted in the fast sequential technique, which is a simple way to mimic the multi-element function. However, it only works for FAAS applications. Moreover, simultaneous multielement ET-AAS systems for analysis have also been placed on the market, although there are some spectral limitations. It also has the drawback of using the same time and temperature programme for all elements. In the future, further developments in the multielement technique can be envisaged which will resort to continuum sources as well as CCD and other multiwavelength detectors. 

Water pollution remains a serious problem in the United States and in other industrial countries. The photo shows land left over after strip mining in Belmont County, Ohio. The various water pools shown are contaminated with waste chemicals. The large pool to the right of center contains sulfuric acid. The smaller pools contain manganese and cadmium. Trace metals in contaminated water samples are often determined by a multielement technique such as inductively coupled plasma rnassj spectrometry or inductively coupled plasma atomic emission spectroscopy. Botft these methods are discussed in this chapter. 

Results for elements in aerosol samples which are obtained by multielement techniques from data sets from which information about the sources of the components can be extracted (Gordon 1980). Such methods which make use of data obtained at receptor points are called receptor models. The most important receptor models are chemical mass balances (CMB), enrichment factors, time series correlation, multivariate models and spatial models (Cooper and Watson 1980 Gordon 1988). Dispersion modeling has also been used to explain the... 

Today, the field of trace metal analytical chemistry is dominated by a few single-, oligo-and multielement techniques having high detection power ... 

An optical multichannel analyzer was used to obtain both peak height and peak area and was corrected for background. Results indicate either peak height or peak area can be used analytically except under electronic overload conditions. The method was used with a U. S. Geological Survey rock sample to determine Al, Fe, Ca, and Ti. The multielement technique compared favorably with concentrations of the four elements as reported by the U. S. Geological Survey. 

Neutron activation analysis is a powerful nondestructive multielement technique that can be applied to the determination of over 60 elements in a broad range of matrices. The method involves activation of the sample in a source of neutrons followed by y-ray spectrometry to identify and quantify the induced... 

Standard solutions of inorganic species, both non-metals and metals, are particularly widely used in laboratories. Multielement metal standards, for use in ICP emission spectroscopy and other multielement techniques, must be backed with a guarantee that high-purity components are used in their formulation otherwise, trace impurities in the individual ingredients may contribute significantly toward total quantities of the very elements it is required to measure. Undesirable blanks of this kind are easily overlooked and can seriously degrade analytical performance. 

X-ray fluorescence XRF is one of the longest established techniques for trace elemental analysis. While XRF is not a very sensitive technique, its main advantages are the capability for direct solid sample analysis combined with multielement determinations. While sample pretreatment of solids can be substantially reduced or even omitted in some cases, perfect matching between standards and samples is required for accurate results, because of severe matrix effects. The main application field of XRF is, therefore, the analysis of solid materials, such as metallurgical and geological samples, where solid standards are readily available. Liquid samples can be analyzed either directly in special cells or by using preconcentration techniques with solid sorbents, which can be directly analyzed after sample loading. More modern methods, like total-reflection X-ray fluorescence, which is a multielement technique mainly for solutions, or particle-induced X-ray emission, which is a micromethod with some spatial resolution, have found limited application in some special areas. For speciation purposes, species separation has to be carried out in front in an offline mode. 

As mentioned above, virtually the entire periodic table is used in some geological applications. The growth of multielement techniques such as XRF and latterly inductively coupled plasma-atomic emission spectrometry (ICP-AES) and inductively coupled plasma-mass spectrometry (ICP-MS) has led to an increasingly wide suite of elements being determined routinely in geochemical analyses. Certain groups of elements are particularly important analytes in geochemical analyses. 

Different techniques are in use for analysis of the filtration fraction and concentrates. Most often multielement techniques such as ICP AES/MS and X-ray fluorescence (XRF) spectrometry are applied. Use of electrochemical methods and different techniques of atomic absorption spectrometry (AAS) is also possible. 

Requiring only relatively simple equipment, XRF spectroscopy is a powerful and convenient nondestructive multielement technique for bulk analysis of a variety of materials that features detection limits in the pgperkg range for conventional spectrometer types. By employing special excitation conditions (see below), sub-pgperg detection limits can be achieved for most elements heavier than sodium. 

The radiation source used in AAS is an HCL or an EDL, and a different lamp is needed for each element to be determined (except for the new continuum source system discussed earlier). Because it is essentially a single-element technique, AAS is not well suited for qualitative analysis of unknowns. To look for more than one element requires a significant amount of sample and is a time-consuming process. For a sample of unknown composition, multielement techniques such as XRF, ICP-mass spectrometry (ICP-MS), ICP-OES, and other atomic emission techniques are much more useful and efficient. 

Jochum, K.P., Laue, H., Seufert, H.M., Dienemann, C., Stoll, B., Pfander, I, Flanz, M., Achtermann, H., Hofmann, A.W. (1997) Multi-ion counting-spark source mass spectrometry (MIC-SSMS) a new multielement technique in geo- and cosmochercastvy. Fresenius Journal of Analytical Chemistry, 359,385-389. 

Mass spectrometry as a multielement technique has the advantage that many metal ions can be detected and quantitatively determined at once. In bulk materials such as steel [245] or refractory metals [246], elements can be determined by means of low-resolution glow-discharge... 

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