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• W161435194 abstract "This thesis is based on developments in mass spectrometry(MS), gas chromatography (GC) and combined gaschromatography-mass spectrometry (GC-MS) as analyticaltechniques, and specific applications of thesedevelopments and traditional MS and GC-MS to the analysisof organic samples. The majority of this work has beenpublished in the refereed scientific literature.A detailed theoretical study was undertaken into therelationships between chromatographic resolution incombined GC-MS and carrier gas flow rate. The influencethat the type of GC-MS interface has on optimum flow raterequirements was quantified. A simple equation relatingcolumn length, column 'hold-up' time and volumetric flowrates in directly coupled capillary GC-MS was derived,facilitating the setting of the appropriate optimum gasflow in this mode.Average linear gas velocities and flow rates required todeliver optimum performance for a variety of columndiameters, carrier gases and types of GC-MS interfacewere reported, together with the 'hold-up' times andinlet pressures necessary to deliver these values. Thedependence between carrier gas flow rates, average linearvelocities and temperature programming was determined fora number of GC-MS interface and flow controlcombinations. Discrimination caused by the 'open-split'interface in GC-MS was examined, and a numericalrelationship was established between GC oven temperatureand effluent yield in temperature programmed analyses.A GC-MS screening procedure for a large group of targetanalytes was created using a 'bench-top' quadrupole massspectrometer, enabling automatic detection at tracelevels of genuine or potential 'positives' from crudeextracts. Two representative ions of the target substancehad to occur in the correct ratio and at a specific andautomatically adjusted retention time for a 'positive'report. For maximum sensitivity a number of time windowswere created, and selected ion monitoring of the twocharacteristic ions for each target compound was carriedout. Although the protocol was developed for screeningextracts of biological fluids for drugs, it could beapplied to screening for target compounds from anymatrix.The technique of 'Selected Reaction Monitoring' offragmentations within the first field-free region of adouble-focussing instrument of Nier-Johnson geometry wasdeveloped, and applied to the quantitative determination of drugs and drug metabolites from body fluid extractsusing stable isotope labelled internal standards. Thismethod, an aspect of the now widely adopted 'MassSpectrometry/Mass Spectrometry' (MS/MS) techniques,greatly increased the specificity of the detection oftarget compounds. Warfarin from human blood and N-hydroxyphenacetin from human urine were quantified by thistechnique. These two examples were among the first to usea conventional geometry mass spectrometer in this way forthe simultaneous monitoring of daughter ions fromdifferent parents from the first field-free region of thespectrometer.Conventional low and high resolution MS and GC-MS wereapplied to the analysis of essential oils, waspsecretions and plant gums and waxes. The essential oilsof six hop cultivars were analysed in detail,particularly with respect to the levels of selineneisomers. Commercial extracts of Boronia megastigmaflowers were analysed by GC-MS; (Z)-heptadec-8-ene anddodecyl acetate were identified as major components,together with the new oxygenated sesquiterpene'sesquicineole' in some clones, and some fifty othervolatile components.A library of several hundred reference mass spectra wascompiled to enable analyses on a range of essential oilsto be undertaken. This was made available to the MScommunity via the U.S. National Institutes of Standardsand Technology (NIST) database. A collection of 'Kovats'GC retention indices, important corroborative evidencefor the MS identification of essential oil relatedcompounds, was obtained from a diverse range ofliterature sources for 400 mono- and sesquiterpenes. Thiscollection of data was published as a review article. Based on MS evidence in conjunction with microchemicalreactions and subsequent comparison with authenticstandards, (E,E)-2,8-dimethy1-1,7-dioxaspiro[5.5]-undecane, (E,E)-2-ethy1-7-methy1-1,6-dioxaspiro[4.5]-decane, (Z,E)-2,8-dimethy1-1,7-dioxaspiro[5.5]undecaneand 2-methyl-6-penty1-3,4-dihydro-2H-pyran wereidentified in the mandibular gland secretions ofparasitic wasps. The structures of three newcycloartenone related triterpenes from Gardenia specieswere determined primarily by MS from first principles;these were 9,19-cyclolanostan-3,24-dione, 9,19-cyclolanost-24-en-3,23-dione, and 9,19-cyclolanostan-3,23-dione." @default.
• W161435194 created "2016-06-24" @default.
• W161435194 creator A5080747967 @default.
• W161435194 date "1993-01-01" @default.
• W161435194 modified "2023-09-26" @default.
• W161435194 title "Mass spectrometry and gas chromatography in chemical analysis and identification : experimental factors and case studies" @default.
• W161435194 hasPublicationYear "1993" @default.
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