Trace analysis with speciation

High performance liquid chromatography coupled with hydride generation-direct current plasma emission spectrometry has been used for trace analysis and speciation studies of methylated organotin compounds in water [263],... 

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. 

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 ICP-MS has become the technique of choice for the determination of elements in a wide range of liquid samples at concentrations in the ng L 1 to [igL-1 range. Typical applications of ICP-MS are multi-element analysis of liquids (even with high solid contents) element speciation by hyphenation to chromatographic techniques continuous on-line gas analysis multi-element trace analysis of polymers and trace analysis in high-purity materials. ICP-MS is routinely used for quality control purposes. 

Table 8.80 shows the present status of speciation methodology. For trace-metal speciation, atomic absorption detectors feature a relatively high absolute detection limit (10 pg level), as compared to the 0.1 to 1 pg sensitivity level for molecular ion MS techniques as well as for MIP-AES. The detection limit of LEI-ToFMS is in the attogram range. Speciation has been reviewed [550]. Various monographs deal with speciation analysis [542,551,552]. 

Multi-element trace analysis is an important prerequisite for the quality assurance of foodstuffs with respect to the characterization of non-essential, toxic and essential (nutrient) elements as pollutions or as mineral elements relevant to health. Contamination with heavy metals such as Cd, Pb or Hg has become a serious problem with increasing environmental (artificial) contamination e.g., due to industrial pollution. The increasing use of inorganic mass spectrometric techniques (especially of ICP-MS) in the analysis of foodstuffs for multi-element analysis of trace elements or the detection of selected elements and species at a low concentration level has resulted from advances in very sensitive and quantitative measurements of metals, metalloids and several non-metals, including their speciation. 

Every coupling application favors one part of the coupling system. A dominating chromatography part leads to the speciation analysis [5,6,26,27]. The elemental specific detection facilities of atomic spectrometry are strongly favored over the multielement capabilities. An inversion of this construction leads to multielement trace analysis in complex matrices with the use of chromatographic equipment as powerful preconcentration and matrix elimination tool [13k The ability of chromatography for a further time resolution between the separated traces is not really required because of the excellent elemental specific detection capabilities of atomic spectrometry. 

SFE is an efficient and fast extraction technique that fits well with green chemistry strategies. The broadest applications of SFE can be found in food, environmental, and pharmaceutical analysis, in industrial and biomedical laboratories, and in speciation analysis [86, 88, 93-97]. Table 6.13 presents selected examples of the use of SFE in trace analysis. 

Nash et al. (2000) (Methodologies for determination of antimony in terrestrial environmental samples). The review by Tolg (1987) (Extreme trace analysis of the elements -the state of the art today and tomorrow) is an insightful review by an experienced trace analyst concentrating on atomic spec-trometric methods including AAS, OES, XRE, MS with many variants of excitation. A table is provided comparing the capability of determinative methods listing the method, the specific technique, limit of determination, matrix effects, multielement determination, and speciation analysis. Methods compared include AAS, ZAAS, OES-DCP, OES-ICP, OES-MIP, OES-HC, EANES, AES, XRS, MS, NAA, voltammetry, LAS and fluorimetry. 

The analysis of trace metals in the aqueous environment has been of interest for many years. As knowledge of the toxicity and the mechanism of toxicity of these metals has expanded, the need for more sensitive analysis has also increased. More recently, attention has been focused on the widely varying effects of different chemical species of the same element in the environment and increased sensitivity combined with speciation has been needed. 

Ma RL, Woods G, and McLeod CW (1999) Microcolumn field sampling and flow injection analysis A strategy for enhanced trace analysis and element speciation. In Sanz-Medel A (ed.) Flow Analysis with Atomic Spectrometric Detectors, pp. 439—458. Amsterdam Elsevier. 

In the last decade speciation (the determination of the species of an element, i.e., its oxidation state or its compounds) has become more important than trace element determination. Speciation analysis is obtained by hyphenated techniques, i.e.. coupling of, for example, a chromatographic separation technique to a very sensitive elemental detector. As NAA cannot measure on-line, the role of NAA becomes less important. However, for the development of separation and preconcentration techniques, the use of radiotracers with very high specific activity is an outstanding tool, as these... 

In the early days of trace element speciation studies using chromatography coupled with ICP-MS, researchers had no choice but to interface their own LC pumps, columns, autosamplers, and so forth to the ICP mass spectrometer, because off-the-shelf systems were not commercially available. However, the analytical objectives of a research project are a little different from the requirements for routine analysis. With a research project, there are fewer time constraints on optimizing the chromatography and detection parameters, whereas in a commercial environment, there are... 

The potential of LC-ICP-MS for trace metal speciation of non-volatile species has been widely discussed. Of particular interest in the area of speciation analysis with LC-ICP-TOF-MS is the recent development of hyphenated isotope ratioing-based methods. The simultaneous extraction capability of ICP-TOF-MS makes it especially attractive for transient isotope ratios or isotope dilution measurements. Vazquez Pelaez et al. compared the characteristics of ICP-TOF-MS and quadrupole ICP-MS with respect to isotope ratio precision for elemental... 

Interfacing of GC/HPLC with Direct Current Plasma (DCP) Emission Spectroscopic Detection for Trace Metal Analysis and Speciation... 

There is still, therefore, room for improvement in MDLs for those elemental species not capable of forming hydrides on-line, post-column (HPLC) or pre-column (GC). If ICP/MS continues to develop as it has for chromatographic interfacing, then it will clearly lend itself to solving all or most of the lingering problems in trace metal analysis and speciation with practical samples. It could, in the long run, become the only really useful and practical analytical technique for performing trace metal speciation at veiy low levels, sub-ppb. It is not clear that GC/HPLC-... 

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