Plasma elemental analyses

Elemental Analysis Atomic absorption spectrometry X-Ray fluorescence spectrometry Plasma emission spectrometry... 

Gases and vapors of volatile liquids can be introduced directly into a plasma flame for elemental analysis or for isotope ratio measurements. Some elements can be examined by first converting them chemically into volatile forms, as with the formation of hydrides of arsenic and tellurium. It is important that not too much analyte pass into the flame, as the extra material introduced into the plasma can cause it to become unstable or even to go out altogether, thereby compromising accuracy or continuity of measurement. 

There are two basic types of instrument used in plasma emission analysis, namely the simultaneous and the sequential multi-element spectrometer. 

Leary JJ, Brookes AE, Dorrzape AF Jr, Golightly DW 1982) An objective function for optimization techniques in simultaneous multiple-element analysis by inductively coupled plasma spectrometry. Applied Spectroscopy 36 37-40. 

ICP-AES and ICP-MS analyses are hampered in almost all cases by the occurrence of sample matrix effects. The origins of these effects are manifold, and have been traced partly to physical and chemical aerosol modifications inside sample introduction components (nebulisation effects). Matrix effects in ICP-AES may also be attributed to effects in the plasma, resulting from easily ionised elements and spectral background interferences (most important source of systematic errors). Atomic lines are usually more sensitive to matrix effects than are ionic lines. There exist several options to overcome matrix interferences in multi-element analysis by means of ICP-AES/MS, namely ... 

Applications Over the last 20 years, ICP-AES has become a widely used elemental analysis tool in many laboratories, which is also used to identify/quantify emulsifiers, contaminants, catalyst residues and other inorganic additives. Although ICP-AES is an accepted method for elemental analysis of lubricating oils (ASTM D 4951), often, unreliable results with errors of up to 20% were observed. It was found that viscosity modifier (VM) polymers interfere with aerosol formation, a critical step in the ICP analysis, thus affecting the sample delivery to the plasma torch [193]. Modifications... 

In AFS, the analyte is introduced into an atomiser (flame, plasma, glow discharge, furnace) and excited by monochromatic radiation emitted by a primary source. The latter can be a continuous source (xenon lamp) or a line source (HCL, EDL, or tuned laser). Subsequently, the fluorescence radiation is measured. In the past, AFS has been used for elemental analysis. It has better sensitivity than many atomic absorption techniques, and offers a substantially longer linear range. However, despite these advantages, it has not gained the widespread usage of atomic absorption or emission techniques. The problem in AFS has been to obtain a... 

Gijbels [355] has reviewed the elemental analysis of high-purity solids by mass spectrometry. For applications of plasma-source mass spectrometry, see ref. [353],... 

Entwistle, J. A. and P. W. Abrahams (1997), Multi-element analysis of soils and sediments from Scottish historical sites. The potential of inductively coupled plasma-mass spectrometry for rapid site investigation, /. Archaeol. Sci. 24, 407-416. 

Que Hee SS, Boyle JR. 1988. Simultaneous multi-elemental analysis of some environmental and biological samples by inductively coupled plasma atomic emission spectrometry. Anal Chem 60 1033-1042. 

The AAS technique is in competition with plasma emission spectroscopy (Section 2.6) for the elemental analysis of plastic, rubber and other polymeric... 

Elemental Speciation - New Approaches for Trace Element Analysis Discrete Sample Introduction Techniques for Inductively Coupled Plasma Mass Spectrometry... 

Ciucci A., Palleschi V., Rastelli S., Salvetti A., Tognoni E., New procedure for quantitative elemental analysis by Laser Induced Plasma Spectroscopy, Appl. Spectrosc., 1999 53 (8) 960. 

The potential for the employment of plasma emission spectrometry is enormous and it is finding use in almost every field where trace element analysis is carried out. Some seventy elements, including most metals and some non-metals, such as phosphorus and carbon, may be determined individually or in parallel. As many as thirty or more elements may be determined on the same sample. Table 8.4 is illustrative of elements which may be analysed and compares detection limits for plasma emission with those for ICP-MS and atomic absorption. Rocks, soils, waters and biological tissue are typical of samples to which the method may be applied. In geochemistry, and in quality control of potable waters and pollution studies in general, the multi-element capability and wide (105) dynamic range of the method are of great value. Plasma emission spectrometry is well established as a routine method of analysis in these areas. 

On the basis of the preceding discussion, it should be obvious that ultratrace elemental analysis can be performed without any major problems by atomic spectroscopy. A major disadvantage with elemental analysis is that it does not provide information on element speciation. Speciation has major significance since it can define whether the element can become bioavailable. For example, complexed iron will be metabolized more readily than unbound iron and the measure of total iron in the sample will not discriminate between the available and nonavailable forms. There are many other similar examples and analytical procedures that must be developed which will enable elemental speciation to be performed. Liquid chromatographic procedures (either ion-exchange, ion-pair, liquid-solid, or liquid-liquid chromatography) are the best methods to speciate samples since they can separate solutes on the basis of a number of parameters. Chromatographic separation can be used as part of the sample preparation step and the column effluent can be monitored with atomic spectroscopy. This mode of operation combines the excellent separation characteristics with the element selectivity of atomic spectroscopy. AAS with a flame as the atom reservoir or AES with an inductively coupled plasma have been used successfully to speciate various ultratrace elements. 

Bethell. P. H. and Smith, J. U. (1989). Trace-element analysis of an inhumation from Sutton Hoo, using inductively coupled plasma emission-spectrometry - an evaluation of the technique applied to analysis of organic residues. Journal of Archaeological Science 16 47-55. 

Durrant, S. F. (1992). Multi-element analysis of environmental matrices by laser ablation inductively coupled plasma mass spectrometry. Analyst 117 1585-1592. 

All solid materials were analyzed by XRD, SEM, infrared, BET surface area, and inductive coupled arc plasma. All up flow samples and co-precipitation samples resulted in acceptable elemental analysis when analyzed for Bi, Fe, and Mo. 

The advantages of using plasma emission sources include the ability to perform multi-element analysis, a calibration linear dynamic range of more than three orders of magnitude and for some elements the limits of detection are comparable to those found by GFAAS. The ability to perform multi-element analysis is essential when the purpose of the experiments is to study element interaction effects. 

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