Claudia A. Ponce de León

Elemental speciation by chromatographic separation with inductively coupled plasma mass spectrometry detection

Separation techniques coupled to inductively coupled plasma mass spectrometry (ICP-MS) is reviewed. ICP-MS technique is described briefly. Coupling of the different separation techniques are described, together with the most common applications used for each technique that has been described in the literature. An overview for the future of separation techniques coupled to ICP-MS with regard to elemental speciation is discussed.

Chiral speciation of selenoamino acids and selenium enriched samples using HPLC coupled to ICP-MS

The chiral separation of nine selenoamino acids using a crown ether HPLC column coupled to ICP-MS for detection is described. Three different temperatures were investigated for the separation of the enantiomers of individual amino acids and for a mixture of eight selenoamino acids. Although complete resolution was not achieved, better resolution of the mixture was obtained at higher temperatures. Selenium enriched onion, garlic and yeast were also analyzed. Two different extraction methods for the samples are compared; water extraction and a pepsin enzymatic extraction. Some of the selenoamino acid enantiomers are identified for the different extraction methods. Comparison is also made with earlier reported ion pairing separations for some of these selenoamino acids.

Sequential extractions of selenium soils from Stewart Lake: total selenium and speciation measurements with ICP-MS detection

Different techniques have been employed in order to evaluate the most efficient procedure for the extraction of selenium from soil as required for speciation. Selenium contaminated sediments from Stewart Lake Wetland, California were used. A strong acid mineralization of the samples gives quantitative total selenium, which is then used to estimate recoveries for the milder extraction methods. The different extraction methodologies involve the sequential use of water, buffer (phosphate, pH 7) and either acid solution (e.g. HNO3 or HCl) or basic solutions (e.g. ammonium acetate, NaOH or TMAH). Pyrophosphate extraction was also evaluated and showed that selenium was not associated with humic acids. The extractants were subsequently analyzed by size exclusion chromatography (SEC) with UV (254 and 400 nm) and on-line ICP-MS detection; anion exchange chromatography, and ion-pair reversed phase chromatography with ICP-MS detection. For sequential extractions the extraction efficiencies showed that the basic extractions were more efficient than the acidic. The difference between the acidic and the basic extraction efficiency is carried to the sulfite extraction, suggesting that whatever is not extracted by the acid is subsequently extracted by the sulfite. The species identified with the different chromatographies were selenate, selenite, elemental selenium and some organic selenium.