Development of an on-line UV decomposition system for direct coupling of liquid chromatography to atomic-fluorescence spectrometry for selenium speciation analysis

Speciation analysis of four selenium species (selenite, selenate, selenocystine, and selenomethionine) has been performed by on-line coupling of liquid chromatography (LC), UV decomposition, hydride generation (HG), and atomic-fluorescence spectrometry (AFS). Because only selenite (Se^IV) can generate hydrides, on-line conversion of organic and inorganic selenium species is discussed. Preliminary study showed that the use of only UV light was not sufficient to reduce selenate, because no absorption is observed for this compound at the main wavelength of the low-pressure mercury lamp (253.7 nm). Thus, new conditions based on addition of a reducing reagent (I⁻) were developed. Mechanisms of action are proposed to explain selenium species conversions. Because of their compatibility with on-line treatment, phosphate buffers were used for chromatographic separation on an anion exchange column (Hamilton PRP-X100). Detection limits (19–60 pg Se) and repeatability of the technique were close to those obtained by conventional quadrupole ICPMS. Applications to real samples such as water and oysters are presented and emphasize the robustness of the system.     

Urine NMR Metabolomic Study on Biochemical Activities to Investigate the Effect of P. betle Extract on Obese Rats

Applied Biochemistry and Biotechnology - The present studies are to evaluate the ability of PB to induce weight loss and urine metabolite profile of Piper betle L. (PB) leaf extracts using...     

Matrix-matched quantitative analysis of trace-elements in calcium carbonate shells by laser-ablation ICP–MS: application to the determination of daily scale profiles in scallop shell (<Emphasis Type="Italic">Pecten maximus</Emphasis>)

A micro-scale method has been developed for analysis of trace-element concentration profiles in the calcium carbonate shell of the Great Scallop (Pecten maximus). UV laser ablation at 266-nm coupled with ICP–MS detection was used to analyse daily calcite striae of shell samples to obtain high temporal resolution of trace element incorporation. Analysis of scallop shells was carefully examined to determine the quality of calcium carbonate ablation and calibration. An accurate external calibration method based on matrix matching was developed. Twelve sodium-free enriched calcium carbonate standards containing up to twenty-four elements were prepared, by co-precipitation with aqueous ammonia and NH₄HCO₃, and subsequently back-calibrated in the laboratory. These CaCO₃ standards were found to be homogenous and their use enabled sensitive quantitative analysis (detection limits of a few ng g⁻¹) over a wide range of concentrations (0.1 to 500 μg g⁻¹). Use of these CaCO₃ standards was also evaluated by analysis of three calcium-rich certified reference materials. Because calibration was consistent with the certified results, this analytical method is a sensitive tool for analysis of environmental calcium carbonate matrices. Repeated analysis of scallop shell samples collected simultaneously at the same location showed that the trace elements are homogeneously distributed along a stria. The reliability of such in-situ records of biogenic calcium carbonate (scallop shells) is apparent from the inter-individual and inter-annual reproducibility of the trace element profiles.     

Glycosylated VCAM-1 isoforms revealed in 2D western blots of HUVECs treated with tumoral soluble factors of breast cancer cells

Background  

Several common aspects of endothelial phenotype, such as the expression of cell adhesion molecules, are shared between metastasis and inflammation. Here, we analyzed VCAM-1 variants as biological markers of these two types of endothelial cell activation. With the combination of 2-DE and western blot techniques and the aid of tunicamycin, we analyzed N-glycosylation variants of VCAM-1 in primary human endothelial cells stimulated with either TNF or tumoral soluble factors (TSF's) derived from the human breast cancer cell line ZR75.30.