REFINEMENTS IN ANALYTICAL MS/MS. NATURAL PRODUCT STUDIES
Abstract
Studies involving characterization of natural products are utilized to demonstrate and stimulate refinements in tandem mass spectrometry (MS/MS). A study of nutmeg demonstrates the potential for more in-depth characterization of a complex mixture by MS/MS. One new component, a dehydrodiphenylpropanoid derivative of myristicin was discovered. This compound was identified in the presence of an isomer by use of parent scans. Also included is data comparing high energy and low energy collision induced dissociation (CID) spectra taken on the same sample. MS/MS is used to characterize a new natural product, dehydrosalsolidine in Carnegiea gigantea. The ability is demonstrated to differentiate whether or not a species is an artifact created in lengthy isolation procedure or is actually present in the plant. A unique set of experiments shows the potential of linking desorption ionization, specifically laser desorption (LD) with MS/MS. The analytical utility of LD-MS/MS is demonstrated by analyzing for the quaternary alkaloid candicine in a series of aqueous extracts of cactus tissue. This method is faster and more specific than TLC and is suitable for surveying cacti for suspected quaternary alkaloids with an estimated detection limit of 0.1 (mu)g/1 mg dry weight. During this study a need arose to be able to acquire mass spectral data more rapidly. To do this software was written to allow computer scanning of the magnet. Details of this software are included. Results of a systematic study of experimental variables in LD-MS/MS using a high power pulsed neodynium YAG laser are also given. A study on the maytansinoid trewiasine shows that quadrupole MS/MS is applicable to fragile biomolecules of high molecular weight (750 amu), even when they do not generate molecular ions. A multiple ion monitoring assay was developed using the two highest mass ions in the CI mass spectrum at m/z 689 and at m/z 659, both of which generate fragments diagnostic of the parent structure in their MS/MS spectra. A detection limit for direct analysis of seed material of 100 ng in a 4 mg sample was established. Also a detection limit of approximately 1 ng was established when dealing with the pure compound. A reduction in overall chemical noise is shown when methanol extraction is employed prior to analysis. This extraction preconcentrates the analyte and makes detection of the compound at low levels easier.
Degree
Ph.D.
Subject Area
Analytical chemistry
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