scholarly journals Determination of molecular masses for petroleum distillates by simualted distillation

2012 ◽  
Vol 4 (5) ◽  
pp. 43-55 ◽  
Author(s):  
Lante Carbognani
Keyword(s):  
Stationary Phases ◽  
Size Exclusion ◽  
Chromatographic Separations ◽  
Calibration Standards ◽  
Hydrocarbon Group ◽  
Simulated Distillation ◽  
Size Exclusion Chromatographic ◽  
Petroleum Distillates ◽  
Molecular Masses

Determination of Molecular Mass (MM) for petroleum distillates is explored for selected samples viaHigh Temperature Simulated Distillation (HTSD). MM is determined as a by-product from routineHTSD carried out using open wall capillary columns coated with apolar stationary phases. No samplepre-separation into hydrocarbon group-types is required. Determined MM values were validated with resultsachieved via correlations based on specific gravity and refractive index. Furthermore, determined MM withthe former methodologies were found to match mass spectrometric determinations carried out for the basicpolar components present within the studied samples. Moreover, HTSD analyzed petroleum distillates areproposed as more representative calibration standards for size exclusion chromatographic separations, thusopening the feasibility of extrapolating MM determination for non volatile petroleum residua.

scholarly journals Size Exclusion Chromatographic Cleanup for GC/MS Determination of Organophosphorus Pesticide Residues in Household and Vehicle Dust

2002 ◽  
Vol 85 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Thomas F Moate ◽  
Matthew Furia ◽  
Cynthia Curl ◽  
Juan F Muniz ◽  
Jianbo Yu ◽  
...  
Keyword(s):  
Organophosphorus Pesticides ◽  
Organophosphorus Pesticide ◽  
Fruit Production ◽  
Size Exclusion ◽  
Gas Chromatography Mass Spectrometry ◽  
Selected Ion Monitoring ◽  
Size Exclusion Chromatographic ◽  
Tree Fruit ◽  
Exclusion Chromatography

Abstract Size exclusion chromatography (SEC) was used as a cleanup method for the analysis of organophosphorus pesticides in household and vehicle dusts. The pesticides investigated were diazinon, methyl parathion, chlorpyrifos, malathion, phosmet, and azinphosmethyl. These compounds are of interest due to their use in agricultural tree fruit production and/or urban pest control. Pesticides were determined via gas chromatography/mass spectrometry with selected-ion monitoring and cool on-column injection. The lower limit of method validation was 0.20 μg/g. Method limits of detection in dust ranged from 0.012–0.055 μg/g. Dust samples were collected with vacuums from the homes and vehicles of people living and working in a rural agricultural region in the central part of Washington State. The analytes were extracted from the dust by sonication in acetone. The extracts were solvent-exchanged to cyclohexane, frozen, thawed, and centrifuged prior to SEC injection. Following SEC, the eluent was split into 2 fractions, concentrated, and injected on-column into the gas chromatograph. This method represents the first complete publication describing the SEC cleanup of organophosphorus pesticides in dusts. Recoveries of pesticides in dusts ranged from 63.5–110.8 ± 4.9–19.6% over a fortification range of 0.20–10.00 μg/g. This optimized, automated, and reproducible SEC method does not require further treatment or cleanup for trace determination of these organophosphorus pesticides.

scholarly journals Chitinolytic enzymes from bacterium inhabiting human gastrointestinal tract -- critical parameters of protein isolation from anaerobic culture.

2011 ◽  
Vol 58 (2) ◽  
Author(s):  
Jarmila Dušková ◽  
Galina Tishchenko ◽  
Evgenia Ponomareva ◽  
Jiří Šimůnek ◽  
Ingrid Koppová ◽  
...  
Keyword(s):  
Gastrointestinal Tract ◽  
Size Exclusion ◽  
Critical Parameters ◽  
Protein Isolation ◽  
Chromatographic Separations ◽  
Healthy Human ◽  
Chitinolytic Enzymes ◽  
Sds Page ◽  
Clostridium Paraputrificum

The object of this study are chitinolytic enzymes produced by bacterium Clostridium paraputrificum J4 isolated from the gastrointestinal tract of a healthy human. In particular, we focus on the development of purification protocols, determination of properties of the enzymes and their activity profiles. The process of bacteria cultivation and isolation of chitinolytic complex of enzymes showing specific activities of endo-, exo-chitinase and N-acetyl-β-glucosaminidase was optimized. A range of various purification procedures were used such as ultrafiltration, precipitation, chromatographic separations (ion-exchange, size exclusion, chromatofocusing) in altered combinations. The optimal purification protocol comprises two or three steps. Individual samples were analyzed by SDS/PAGE electrophoresis and after renaturation their activity could be detected using zymograms. Mass spectroscopy peptide fragment analysis and MALDI analysis of the purest samples indicate presence of endochitinase B (molecular mass about 85 kDa) and of 60-kDa endo- and exochitinases.

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