Chromatography speciation

Haddad, P. Kalambaheti, C. (1991) Advances in ion chromatography speciation of mg L 1 levels of metallo-cyanides using ion interaction chromatography. Anal. Chim. Acta., 250, 21—36. 

In this work ion-exchange and gel-permeation chromatography coupled with membrane filtration, photochemical oxidation of organic metal complexes and CL detection were applied to the study of the speciation of cobalt, copper, iron and vanadium in water from the Dnieper reservoirs and some rivers of Ukraine. The role of various groups of organic matters in the complexation of metals is established. 

Inoue Y, Kawabata K (1993) Speciation of organotin compounds by inductively coupled plasma mass spectrometry combined with liquid chromatography. Journal of the Mass Spectrometry Society of Japan, 41 (4) 245-251. 

Tutschku S, Mothes S, Dittrich K (1994) Determination and speciation of organotin compounds by gas chromatography-microwave induced plasma atomic emission spectrometry. Journal of Chromatography A, 683 269-276. 

Zhang X, Cornelis R, De Kimpe J, and Mees L (1996) Arsenic speciation in serum of uraemic patients based on liquid chromatography with hydride generation atomic absorption spectrometry and on-line UV photo-oxidation digestion. Anal Chim Acta 319 177-185. 

HPLC (in both NP and RP modes) is quite suitable for speciation by coupling to FAAS, ETAAS, ICP-MS and MIP-MS [571,572]. Coupling of plasma source mass spectrometry with chromatographic techniques offers selective detection with excellent sensitivity. For HPLC-ICP-MS detection limits are in the sub-ng to pg range [36]. Metal ion determination and speciation by LC have been reviewed [573,574] with particular regard to ion chromatography [575]. 

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 Electrochemical techniques, while lacking the wide elemental range and long linear response of some atomic and mass spectrometry technologies, offer a valuable alternative in a number of specific applications, and have particular advantages for direct speciation and anion determination. In ion chromatography, amperometric, potentiometric and conductometric detection is widely used [472], see also Section 4.4.2.5. 

H. De Beer, Metal Speciation by High Performance Liquid Chromatography, PhD. Thesis, Rand Afrikaans University, South Africa (1993). 

Evaporative LC-FTIR is rapidly gaining industrial acceptance as a useful tool in low-MW additive analysis. HPLC has also been coupled with various element-selective detectors. There is significant demand for speciation information for many elements, and the separation ability of chromatography coupled to ICP-MS offers the analyst a versatile tool for such studies. It is apparent that ICP-MS is increasingly being employed for chromatographic detection. Several modes of GC, SFC, LC and CE have been hyphenated with ICP-MS for improved detection limits compared to other traditional methods of detection such as UV-VIS spectroscopy. Inorganic speciation deserves more attention. 

Bloxam et al. [482] used liquid chromatography with an inductively coupled plasma mass spectrometric detector in speciation studies on ppt levels of mercury in seawater. 

In the analysis of clinical, biological and environmental samples it is often important to have information on the speciation of the analyte, e.g. metal atoms. Thus an initial sample solution may be subjected to a separation stage using chromatography or electrophoresis. Measurements may, of course, be made on fractions from a fraction collector, but with plasma sources, interfacing in order to provide a continuous monitoring of the column effluent can be possible. This relies upon the ability of the high-temperature plasma to break down the matrix and produce free ions. 

L. S. Milstein, A. Essader, E. D. Pellizzari, R. A. Fernando, and O. Akinbo. Selection of a Suitable Mobile Phase for the Speciation of Four Arsenic Compounds in Drinking Water Samples Using Ion-exchange Chromatography Coupled to Inductively Coupled Plasma Mass Sectrometry. Environ, lnt., 28(2002) 277-283. 

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. 

Lobinski et al. [72] optimized conditions for the comprehensive speciation of organotin compounds in soils and sediments. They used capillary gas chromatography coupled to helium microwave induced plasma emission spectrometry to determine mono-, di-, tri- and some tetraalkylated tin compounds. Ionic organotin compounds were extracted with pentane from the sample as the organotin-diethyldithiocarbamate complexes then converted to their pentabromo derivatives prior to gas chromatography. The absolute detection limit was 0.5pg as tin equivalent to 10-30pg kg-1. 

Arakawa et al. [96] have pointed out that methyltin compounds may be extracted from complex matrices and analysed by conventional gas chromatography. However, the procedure is lengthy, involving multiple steps where speciation may be altered and vessel adsorption effects may be large. Detection limits achievable with a flame ionization detector are 10-100pg [97],... 

Yang et al. [83] accomplished speciation of organotin compounds using reverse-phase liquid chromatography with inductively coupled plasma mass spectrometric detection. The separation was complete in 6min and detection limits were in the range 2.8-16pg of tin for various species. 

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