Elemental analysis instrument selection

The section Analysis starts with elemental composition of the compound. Thus the composition of any compound can be determined from its elemental analysis, particularly the metal content. For practically all metal salts, atomic absorption and emission spectrophotometric methods are favored in this text for measuring metal content. Also, some other instrumental techniques such as x-ray fluorescence, x-ray diffraction, and neutron activation analyses are suggested. Many refractory substances and also a number of salts can be characterized nondestructively by x-ray methods. Anions can be measured in aqueous solutions by ion chromatography, ion-selective electrodes, titration, and colorimetric reactions. Water of crystallization can be measured by simple gravimetry or thermogravimetric analysis. 

In spite of the excellent capability and advantages (high selectivity and sensitivity) of RIMS for the ultratrace analysis of isotopes with naturally rare abundance in environmental, geological, medical and nuclear samples, no commercial instrumentation is available to date. In contrast to AMS and RIMS as mono-elemental (element-specific) analytical techniques, ICP-MS and LA-ICP-MS possess, in analogy to GDMS and SIMS, have the ability for multi-element analysis and thus could have the widest fields of application. 

To reduce the detrimental effects of spectral interferences on element quantitation, laboratories select the spectral lines that are least affected by the background, and use the background compensation and interelement correction routines as part of the analytical procedure. The instrument software uses equations to compensate for overlapping spectral lines the effectiveness of these equations in eliminating spectral interferences must be confirmed at the time of sample analysis. That is why laboratories analyze a daily interelement correction standard (a mixture of all elements at a concentration of 100mg/l) to verify that the overlapping lines do not cause the detection of elements at concentrations above the MDLs. 

Laser Desorption. A laser microprobe system has been used for surface analysis to detect both organic and inorganic species [89]. Although this instrument was not developed with elemental analysis in mind, studies of selected inorganic compounds have been carried out, and elemental ions have been and can be detected with the system. One other external source that produces atomic ions should be noted here. A laser vaporization metal ion source [90] has produced a wide variety of reactant ions for use in ion-molecule reactivity studies. In almost all cases, pure metals were used to form the ions, and the intent of the research was chemical reactivity studies and not elemental analysis. 

Inductively coupled plasma emission spectrometry is a standard method for trace elemental analysis. While sensitive and selective, these instruments are large and require considerable support solutions... 

Detection techniques of high sensitivity, selectivity, and ease of coupling with sample preparation procedures are of special interest for measuring PGM content in biological and environmental samples. ICP MS, electrothermal atomic absorption spectrometry (ET AAS), adsorptive voltammetry (AV), and neutron activation analysis (NAA) have fotmd the widest applications, both for direct determination of the total metal content in the examined samples and for coupling with instrumental separation techniques. Mass spectrometry coupled with techniques such as electrospray ionization (ESI) and capillary electrophoresis (CE) (e.g., ESI MS", LC ESI MS", LC ICP MS, CE MS", and CE ICP MS) offer powerful potential for speciation analysis of metals. MS is widely used for examination of the distribution of the metals in various materials (elemental analysis) and for elucidation of the... 

Fortunately, there are many different kinds of instruments available. Each instrument has different capabilities and produces somewhat different results. There are many decisions to be made when selecting an instrument to use for the analysis of archaeological materials. Foremost considerations include the type of material to be studied and the questions that are being asked. Based on the material and question, a decision as to the kind of information that is needed can be made (elemental concentrations, isotopic ratios, molecular identification ) and an instrument selected. At the same time, different instrumentation can provide similar data. For example, elemental concentrations can be obtained using XRF, NAA, or ICP/OES. Further decisions are sometimes required involving the precision and quality of the data that are needed. 

Various atomic spectrometric methods form an essential part of the modern instrumental methods of analysis. The most widely used of these methods is atomic absorption spectrometry (AAS). The popularity of AAS can be attributed to its selectivity, simplicity, and convenience in use. The high sensitivity of graphite furnace AAS is very important in many applications. Plasma atomic emission spectrometry (plasma AES) has become more and more important for the determination of traces in a great variety of samples. The complementary nature of plasma AES and AAS capabilities for trace elemental analysis is an important feature of these techniques. Inductively coupled plasma mass spectrometry (ICP-MS) has become a hot analytical technique during the last few years, and is being used in many branches of science. 

In turn, the development of principles of polymer and composite behavior, coupled with the availability of instrumentation to. characterize both morphology and physical properties, has made possible a much better scientific understanding of polymer composites. Further research on phase and interfacial characteristics continues to be productive, especially now that newer instruments permit quantitative elemental analysis of exceedingly small volume elements (Hercules, 1972). The knowledge gained should greatly improve the now rather undeveloped state of polymer selection and design. 

See also Atomic Absorption Spectrometry Principles and Instrumentation. Atomic Emission Spectrometry Principles and Instrumentation. Elemental Speciation Overview. Food and Nutritional Analysis Sample Preparation. Ion-Selective Electrodes Overview. Quality Assurance Reference Materials. Sample Dissolution for Elemental Analysis Dry Ashing Oxygen Flask Combustion Wet Digestion Microwave Digestion. Spectrophotometry Inorganic Compounds. Titrimetry ... 

Since the early 1980s, ICPMS has grown to be one of the most important techniques for elemental analysis because of its low detection limits for most elements, its high degree of selectivity, and its reasonably good precisidn and accuracy. In these applications an ICP torch serves as an atomizer and ionizer. For solutions, sample introduction is accomplished by a conventional or an ultrasonic nebulizer. For solids, one of the other sample-introduction techniques discussed in Section 8C-2, such as spark or laser ablation or glow discharge, are used. Commercial versions of instruments for these various techniques have been on the... 

Plasma source mass spectrometry is a powerful analytical technique for trace element analysis with species selectivity when coupled with a suitable chromatographic sample introduction method. It combines the ability of the analytical plasma to atomize and ionize samples efficiently, with the sensitivity and selectivity of mass spectrometry. Following the commercial introduction of inductively coupled plasma mass spectrometry (ICP-MS) instrumentation in 1983, interest in plasma source MS increased rapidly. The enormous popularity of ICP-MS is not surprising considering the low levels of detection possible for a wide range of elements. In addition, multielement capability and the availability of isotope ratio information help make plasma source MS particularly... 

A variation on depth profiling that can be performed by modern scanning Auger instruments (see Sect. 2.2.6) is to program the incident electron beam to jump from one pre-selected position on a surface to each of many others in turn, with multiplexing at each position. This is called multiple point analysis. Sets of elemental maps acquired after each sputtering step or each period of continuous sputtering can be related to each other in a computer frame-store system to derive a three-dimensional analysis of a selected micro volume. 

HPLC-QFAAS is also problematical. Most development of atomic plasma emission in HPLC detection has been with the ICP and to some extent the DCP, in contrast with the dominance of the microwave-induced plasmas as element-selective GC detectors. An integrated GC-MIP system has been introduced commercially. Significant polymer/additive analysis applications are not abundant for GC and SFC hyphenations. Wider adoption of plasma spectral chromatographic detection for trace analysis and elemental speciation will depend on the introduction of standardised commercial instrumentation to permit interlaboratory comparison of data and the development of standard methods of analysis which can be widely used. 

After matrix removal, samples can be measured using various techniques, such as AAS, AES, ICP, etc. Traditional chemical analysis methods, involving separation and gravimetric, titrimetric or polarographic determination of the elements, are being replaced by a wide selection of instrumental methods. 

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