Liquid chromatography, arsenic compounds

The simplest analytical method is direct measurement of arsenic in volatile methylated arsenicals by atomic absorption [ 11 ]. A slightly more complicated system, but one that permits differentiation of the various forms of arsenic, uses reduction of the arsenic compounds to their respective arsines by treatment with sodium borohydride. The arsines are collected in a cold trap (liquid nitrogen), then vaporised separately by slow warming, and the arsenic is measured by monitoring the intensity of an arsenic spectral line, as produced by a direct current electrical discharge [1,12,13]. Essentially the same method was proposed by Talmi and Bostick [10] except that they collected the arsines in cold toluene (-5 °C), separated them on a gas chromatography column, and used a mass spectrometer as the detector. Their method had a sensitivity of 0.25 xg/l for water samples. 

B.6 Speciation of Arsenic Compounds by Ion-Exchange High-Performance Liquid Chromatography with Hydride Generation Atomic Fluorescence Detection. 

Hansen, S.H., Larsen, E.H., Pritzi, G. and Cornett, C. (1992) Separation of seven arsenic compounds by high performance liquid chromatography with on-line detection by hydrogen-argon flame atomic absorption spectrometry and inductively coupled plasma mass spectrometry./. Anal. At. Spectrom., 1, 629-634. 

Saverwyns, S., Zhang, X.R., Vanhaecke, F., Cornelis, R., Moens, L. and Dams, R. (1997) Speciation of six arsenic compounds using high-performance liquid chromatography inductively coupled plasma mass spectrometry with sample introduction by thermospray nebulisation./. Chromatogr. A, 779, 299-306. 

Jyn Yynn and Wai [267] chelated organoarsenic compounds with sodium bis (trifluorethyl) dithiocarbamate prior to application of high performance liquid chromatography. He applied the technique to mixtures of arsenite, arsenate, dimethylarsonic acid, dimethylarsinic acid and other organoarsenic compounds. 

High performance liquid chromatography (Chapter 4) which is displacing conventional column chromatography (Chapter 6) has found numerous applications in the analysis of organic compounds, also metal organic compounds of mercury, tin, arsenic, manganese copper and lead. It has fewer applications in the determinations of anions and cations. 

U. Kohlmeyer, J. Kuballa, E. Jantzen, Simultaneous separation of 17 inorganic and organic arsenic compounds in marine biota by means of high-performance liquid chromatography/inductively coupled plasma mass spectrometry, Rapid Commun. Mass Spectrom., 16 (2002), 965D974. 

S. N. Pedersen, K. A. Francesconi, Liquid chromatography electrospray mass spectrometry with variable fragmentor voltages gives simultaneous elemental and molecular detection of arsenic compounds, Rapid Common. Mass Spectrom., 14 (2000), 641-645. 

E. H. Larsen, G. Pritzl, S. H. Hansen, Speciation of eight arsenic compounds in human urine by high-performance liquid chromatography with inductively coupled plasma mass spectrometric detection using antimonate for internal chromatographic standardization, J. Anal. Atom. Spectrom., 8 (1993), 557-563. 

Coelho, N.M.M., CoeUio, L.M., de Lima, E.S., Pastor, A., de la Guardia, M. Determination of arsenic compounds in beverages by high-performance liquid chromatography-inductively coupled plasma mass spectrometry. Talanta 66, 818-822 (2005)... 

Liquid chromatography, a seemingly simpler procedure than GC in the speciation analysis of arsenic because it does not require the derivatization stage, also generates a number of potential errors. The selection of chromatographic method involves preliminary evaluation of the solubility of compounds to be separated. The... 

The concentrations of the three arsenicals (75-77) were determined in 37 marine organisms comprising algae, crustaceans, bivalves, fish and mammals by high-performance liquid chromatography/inductively coupled plasma mass spectrometry (HPLC/ICPMS) [170]. All three organoarsenics, which occurred at pg/kg concentrations, were detected in 25, 23 and 17 of the 37 samples analyzed, respectively. The limits of detection were 2-3 pg/kg dry mass. The data illustrate that all three compounds are common minor constituents in practically all marine samples. 

As mentioned above in the context of the analysis of hgnin degradation products, gas chro-matography/mass spectrometry and related methods have been developed as extremely powerful tools for the identification of phenolic compounds. Use of high-pressure liquid chromatography in combination with mass spectrometry adds to the analytical arsenal with respect to the detection of polar, non-volatile compounds but, in particular, the advent of modem ionization techniques, such as ESI and MALDI mass spectrometry, have continued to broaden the analytically governable field of organic chemistry. The latter methods diminish the need of derivatization of polar phenolics to increase the volatility of the analyte. In this section, a more or less arbitrary selection of examples for the application of mass spectrometric techniques in analytical chemistry is added to the cases already discussed above in the context of gas-phase ion chemistry. 

Francesconi, K. Applications of liquid chromatography-electropspray ionization-single quadrupole mass spectrometry for determining arsenic compounds in biological samples. Appl Organomet Chem 2002, 16, 437 145. 

Zheng, B., Hinlelmann, H. Hyphenation of high performance liquid chromatography with sector field inductively coupled plasma mass spectrometry for the determination of ultra-trace level anionic and cationic arsenic compounds in freshwater fish. J Anal At Spectrom 2004,19, 191-195. Pergantis, S. A., Heithmar, E. M., Hinners, T. A. Speciation of arsenic animal feed additives by microbore high-performance liquid chromatography with inductively coupled plasma mass spectrometry. Analyst 1997, 122, 1063-1068. 

Wangkam, S., Pergantis, S. A. High-speed separation of arsenic compounds using narrow-bore high-performance liquid chromatography on-line with inductively coupled plasma mass spectrometry. J Anal At Spectrom 2000, 15, 627-633. 

Morita, M., Uehiro, T. and Fuwa, K. (1981). Determination of Arsenic Compounds in Biological Samples by Liquid Chromatography with Inductively Coupled Argon Plasma-Atomic Emission Spectrometric Detection. Anal. Chem., 53, 1806. 

Figure 3 Instrumental methods for the determination of arsenic compounds (Abbreviations AAS, atomic absorption spectrometry APS, atomic fluorescence spectrometry CE, capillary electrophoresis GC, gas chromatography HG, hydride generation ICP-AES, inductively coupled plasma-atomic emission spectrometry ICP-MS, inductively coupled plasma-mass spectrometry INAA, instrumental neutron activation analysis LC, liquid chromatography MS, mass spectrometry).

There is still a lot of work to do to make CZE a robust method for the determination of arsenic compounds in environmental samples. The proposed methods are too matrix sensitive and the difficulties of connecting CZE to element-specific detectors, such as ICP-MS, are not yet solved. At the moment, liquid chromatography in connection with element-specific detectors is certainly favored over CZE. 

M Slekovec, W Goessler, KJ Irgolic. Inorganic and organic arsenic compounds in Slovenian mushrooms Comparison of arsenic specific detectors for liquid chromatography. Chem Spec Bioavailab 11 115-123, 1999. 

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