Advancements in selenium speciation, fast gas analysis and sample preparation procedures for the chemical analysis of real-world samples.

摘要

The Pulsed Discharge Helium Ionization Detector (PDHID) was compared to the Flame Ionization Detector (FID) and the Thermal Conductivity Detector (TCD) for High Speed Gas Chromatography (HSGC). It was shown that the PDHID is as sensitive as the FID but can be less reproducible. Moreover, the PDHID is more sensitive and more universal than the TCD. The prospect of a portable PDHID was explored but, a required helium purifier uses more power than is feasible for portability. The PDHID was used to detect hydrogen and methane separated from the matrix components of breath samples with over an order of magnitude better sensitivity than methods using an FID or TCD. Limits of detection for dissolved hydrogen and methane using the Rapid Aqueous Sample Extractor (RASE)-GC-PDHID were 7.0 ng/mL and 3.5 ng/mL respectively.; The speciation of selenium compounds from high selenium broccoli (900 μg/g) depends on the extraction conditions. Twenty-seven extraction conditions were explored involving nine different buffering systems between pH 1 and pH 9. In non-buffered extractions of broccoli more than 40% of the spiked Se-methylselenocysteine was not recovered in the filtered solution. However, in buffered extractions losses for Se-methylselenocysteine ranged from 10–20%. Approximately 30% of selenium from broccoli was lost to the atmosphere from buffered extractions. High Pressure Liquid Chromatography coupled to an Inductively Coupled Plasma Mass Spectrometer (HPLC-ICP-MS) for speciating selenium. Changes in speciation were analyte, pH and buffer dependent, but generally higher pH resulted in more highly oxidized selenium compounds.; Partition coefficients for selenium compounds across a small intestine model, the CACO-2 cell monolayer, are presented. Selenium compounds were transformed as they passed across the barrier. Presented are tables of the ratios and masses of compounds expected on the basolateral side of the CACO-2 cell model for selenium standards and popular high selenium foods that have undergone simulated digestions.; Determination of chiro-inositol and the related fagopyritols in Buckwheat are presented for crops grown in two different years as well as the difference between cooked and uncooked samples. 2,2-dimethoxypropane (2,2-DMP) was shown to be a useful drying agent while trimethylsilylimidazole (TMSI) can be used to derivatize inostiols without pyridine.