4 research outputs found
Class Type Separation of the Polar and Apolar Components of Petroleum
Identification
of the heteroatom (nitrogen, sulfur, and oxygen)-containing
compounds of petroleum is of key importance when considering industrial
and environmental issues associated with crude oil production. The
more commonly performed methods of crude oil fractionation are often
insufficient in the extent to which they separate oils, not allowing
defined “molecular” fractions to be obtained. Methods
capable of performing a class type separation are uncommon and are
often extensive and resource and time intensive. Here we report a
method for the separation of crude oils into discrete compound classes.
The method utilizes both ion exchange and normal phase chromatography
to generate fractions of saturated hydrocarbons, aromatic hydrocarbons,
basic compounds, naphthenic acids, and other oxygen-containing species,
carbazoles, sulfones, and thiophenes from small crude oil samples
(∼0.5 g). Assessment of method selectivity with a suite of
model compounds has shown the fractions to be well-defined, with classes
of model compounds isolated within discrete fractions. Application
of the method to five crude oils of varying API gravity (12.1–38.3°)
demonstrates a potential for wide-ranging use. Sample recoveries were
high (77–98%) with simple evaporative losses correlating closely
with total sample loss. Repeatability was also high, demonstrated
by triplicate analyses of model compound mixtures, oils spiked with
model compounds and oils alone. Separation selectivity was further
demonstrated by application of the scheme to the Alaska North Slope
(ANS) crude oil and analysis of fractions by comprehensive two-dimensional
gas-chromatography mass-spectrometry (GC × GC/MS) and/or liquid-chromatography
high-resolution accurate-mass mass-spectrometry methods (LC-HRAM-MS).
Isolation of discrete fractions then allowed excellent separation
(by LC and GC methods) of carbazole, dibenzothiophene, fluorenones,
xanthones, and quinoline fractions. Individual parent and C<sub>1–5</sub> alkyl homologues were easily separated (GC × GC/MS), allowing
high-quality mass spectra (EI) to be obtained for the individual compounds
in many cases. Analysis of fractions by GC × GC/MS also allowed
a series of thioxanones to be identified
Summary of disease scoring method for reading the MaGICAD study angiograms.
*<p>Note that vessels are considered diseased according to criteria outlined in the text.</p
Characteristics of the sample by severity of coronary artery stenoses.
<p>Characteristics of the sample by severity of coronary artery stenoses.</p
Odds ratios per SD increase in uBPA (5.96 ng/ml) of diagnosed coronary artery features comparing age and sex adjusted models, fully adjusted models and fully adjusted models where the severity of disease is further broken down to show 1, 2, and 3 vessel disease (VD).
<p>Note: full adjustment included age, sex, BMI category, occupational social class and diabetes status.</p