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Modern mass spectrometric techniques applied to occupational hygiene analysisFord, Michael James January 2002 (has links)
No description available.
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The elucidation of retention behaviour of molecular interactions on bonded phases in reversed phase liquid chromatographyKayillo, Sindy, University of Western Sydney, College of Science, Technology and Environment, School of Science, Food and Horticulture January 2005 (has links)
Separations depend on the molecular interactions occurring on retentive surfaces. Much time and effort is paid in the design and manufacture of chromatographic surfaces that enhance separation capability. This thesis explores some of the design concepts currently available in the market place, and while doing so, investigates the mode of retention on a range of solute species. The information gained from the investigation of the retention and thermodynamic retention behaviour of stationary phases, along with molecular modelling carried out on their stationary phase ligand conformation assists in the design of stationary phase materials that enhance separations. Results from this study indicate that the aromatic functionality on the Synergi-polar-RP column may be diminished, due to the orientation of the phenyl ring on the stationary phase surface. / Doctor of Philosophy (PhD)
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Novel approaches to enhancing selectivity and efficiency in microscale liquid chromatographyVallano, Patrick T. 06 March 2001 (has links)
For a number of reasons, miniaturization of chromatographic columns has been
a general trend over the past three decades. Methods designed to enhance selectivity
and efficiency can offer improved separation power and speed, expanding on the
advantages of miniaturized columns. This dissertation describes novel approaches in
this direction, focusing on two areas: the development of affinity-type sorbents for
capillary HPLC derived from molecular imprinted polymers (MIPs) and the study of
perfusive electroosmosotic flow (EOF) and its effect on efficiency in capillary
electrochromatography (CEC).
MIPs are synthetic polymers capable of selectively binding a template
molecule incorporated prior to polymerization. MIPs prepared using nortripyline, a
tricyclic antidepressant drug, were employed to screen a simulated chemical library,
consisting of a series of structural analogs and related compounds. A parameter was
introduced to quantify the selective retention of the analytes. Library compounds
containing the major structural features of the template (ring structure and pendant 2��
amine) exhibited the highest affinity for the MIP.
The use of macroporous packings under conditions of electroosmotic perfusion
can result in improved chromatographic efficiencies. In this work, the performance of
CEC columns packed with particles having different nominal pore diameters was
investigated. The results indicate that perfusive EOF can yield significant gains in
efficiency and speed, especially when wide pore packings and dilute buffers are
employed.
A model was developed that estimates the extent of perfusive EOF expressed
as an effective particle diameter, d[subscript p,eff] The results suggest that the observed efficiency
gains are not entirely due to smaller d[subscript p,eff] values and could perhaps be due to a
decreased A term in the wide pore packings.
The electrical conductivity of CEC columns was used to assess intraparticle
flow permeability under conditions of perfusion. Results for the narrow pore (100 ��)
column were in agreement with theory for nonporous spheres, indicating intraparticle
current was negligible, while the wide pore (1000 and 4000��) columns exceeded
theoretical values by a factor of two. These results provide evidence of the existence
of "through-pores" and that intraparticle flow permeability (and potential for improved
efficiency with perfusion) is greatest with wide pore packings. / Graduation date: 2001
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The distribution of organic bases in reverse phase liquid chromatography : a study of mechanismsJayasinghe, Dudley Shelton 05 September 1989 (has links)
The distribution of hydrophobic ionogenic organic compounds
(HIOC's) between aqueous and nonaqueous phases has been
investigated. The HIOC's are aniline and methyl substituted
anilines. The aqueous phases are methanol-water mixed solvents with
varying pH and ionic strength. The nonaqueous phases are silica and
alkyl derivatized silica with ethyl- (C-2), octyl- (C-8), and
octadecyl- (C-18) silanes.
A gas-liquid equilibration method has been developed to
determine the Henry's law constants and the activity coefficients of
methyl anilines in methanol-water mixed solvents. The logarithm of
the Henry's law constants vary quadratically with the volume fraction
of methanol.
The chromatographic study has been performed to investigate the
effect of three mobile phase factors, fraction of methanol, pH, and
ionic strength, on the retention of methyl anilines on different
stationary phases.
The logarithm of mass distribution ratios, log k's, of methyl
anilines vary linearly with the volume fraction of methanol. The
ratios of H / k' of methyl anilines increase with increase in
methanol in the mobile phase, indicating an increase in the activity
coefficients in the stationary phases. This observation is found to
be true for different methyl anilines in different stationary phases.
A partition model is presented to describe the effect of pH and
ionic strength on the retention of HIOC's in the mobile phase. The
variation in log k' among neutral and ionic methyl anilines can be
explained by linear free energy relationships. Equations are
established to predict retention of neutral or ionized methyl
anilines from their octanol-water partition coefficients at any
methanol content in the mobile phase. Acid dissociation constants of
methyl anilines determined from the dependence of log k' on pH are in
close agrement with those determined by potentiometric titrations.
The effect of ionic strength on the retention of both neutral and
ionic species of methyl anilines is negligible. That is, the
contribution from electrostatic energy and salting out effect are not
significant.
The chromatographic study is extended to study the retention of
methyl anilines on silica as a function of pH and methanol at a
constant ionic strength. The dependence of retention on pH is
qualitatively interpreted from an ion exchange reaction between the
dissociated silanol groups in the surface and the ionized methyl
anilines. The effect of methanol on the retention of methyl anilines
and of pyridine on silica is described by a quadratic relationship
between the log k' and volume fraction of methanol. / Graduation date: 1990
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A SPECTROSCOPIC STUDY OF RHODAMINE-6G: DETECTION OF NONABSORBING ANALYTES IN REVERSE-PHASE CHROMATOGRAPHY WITH THE AID OF RHODAMINE-6G (FLUORESCENCE, ABSORPTION)Tsakanikas, Panayotis Dimitrios Sokrates January 1985 (has links)
No description available.
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Studies with an aerosol generation interface for liquid chromatography-mass spectrometryWilloughby, Ross Clark 08 1900 (has links)
No description available.
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Particle beam LC/MS with fast atom bombardmentKirk, John Daniel 05 1900 (has links)
No description available.
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High performance liquid chromatography with new bonded stationary phasesGabelman, Steven Neil 08 1900 (has links)
No description available.
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Interfacing packed column supercritical fluid chromatography with mass spectrometry using the particle beam interfaceBurdetteBurdette, Diana Marguerite 08 1900 (has links)
No description available.
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A swept potential electrochemical detector for high performance liquid chromatographyReardon, Patricia Altagracia Flaquer 05 1900 (has links)
No description available.
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