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Document Type

Thesis - University Access Only

Award Date

2012

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

First Advisor

Douglas Raynie

Abstract

The high temperature and pressure capabilities of the newest LC instruments and the improvements in column technology that resulted in small particle columns and new morphologies like fused-core and monolithic columns imposed the need for methods that enable the selection of chromatographic conditions and columns to achieve the best tradeoff between efficiency and analysis time. Desmet’s kinetic plot method (KPM) can be used to choose optimal column and instrument conditions. The KPM method can be used for both isocratic and gradient elution and is useful in the comparison of different types of chromatographies (HPLC, GC, CEC, SFC). The KPM was used to compare the performance of packed-capillary (0.2 and 0.3 mm) and microbore (2.0 and 2.1 mm) superficially porous and monolithic C18 columns in packed-capillary liquid (isocratic elution), ultrahigh-pressure liquid (isocratic and gradient elution) and supercritical fluid (isobaric elution) chromatography. The goal of this study is to determine which silica substrate (fused-core, monolithic) is more suitable for high efficiency and speed in packed-capillary liquid and ultrahigh-pressure liquid chromatography and to compare the performance obtained in ultrahigh-pressure chromatography using isocratic and gradient elution modes. In SFC, the goal was to determine the kinetic performance parameters that can be obtained using an open tubular capillary column and an alkylphenone as an analyte. The monolithic column was found to outperform the fused-core column for slow separations (using packed-capillary LC in 0.46-2.70 mm/s linear velocity range), but did not provide better performance than the fused-core column at high-speed separations (using UPLC in 0.67-6.76 mm/s linear velocity range). The kinetic performance parameters (minimal plate height, Hmin; maximal plate number, Nmax; optimal plate number, Nopt and optimal velocity, uopt) found for heptanophenone (C7) in packedcapillary LC were for the monolithic column: Hmin=17.58 μm, Nmax=550,000, Nopt=150,000 and uopt=0.98 mm/s and for the fused-core column Hmin=18.08 μm, Nmax=120,000, Nopt=41,000 and uopt=1.05 mm/s and in UPLC were for the monolithic column Hmin=12.17 μm, Nmax=100,000, Nopt=19,000 and uopt=2.56 mm/s and for the fused-core Hmin=5.58 μm, Nmax=120,000, Nopt=52,000 and uopt=3.23 mm/s. In UPLC with isocratic elution, the monolithic column yielded similar Nmax as the fused-core column at pressures that can be obtained using a conventional HPLC. Nevertheless shorter analysis times and higher plate numbers can be obtained with the fused-core column. The Nopt value found for the microbore monolith was significantly lower than that found for the capillary monolith. The open-tubular capillary SFC column provided similar performance to the microbore monolithic and fused-core columns. In UPLC with gradient elution, the monolithic column was found to be less powerful in the gradient mode. The fused-core column allowed maximum throughput and resolution in the gradient mode.

Library of Congress Subject Headings

Liquid chromatography

Description

Includes bibliographical references (pages 100-110)

Format

application/pdf

Number of Pages

126

Publisher

South Dakota State University

Rights

In Copyright - Educational Use Permitted
http://rightsstatements.org/vocab/InC-EDU/1.0/

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