Identification and detection of conjugated quinones by direct LC/MS using NICI enhancement.
Item
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Title
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Identification and detection of conjugated quinones by direct LC/MS using NICI enhancement.
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Identifier
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AAI9119662
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identifier
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9119662
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Creator
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Ng, Kenneth K.
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Contributor
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Adviser: David Locke
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Date
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1991
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Analytical | Chemistry, Polymer
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Abstract
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Sterically hindered phenols have been used effectively as antioxidants in commercial polymers, usually in the low tenths of a percent level. However, the additive itself can be oxidized to its quinone analog to provide new sources of undesirable discoloration. The detection of such colored species can be achieved by analyzing the colored polymer extract using HPLC with UV/Visible detection. The identification can be achieved only if standards are available, otherwise isolation or direct liquid chromatography/mass spectrometry (LC/MS) is needed. Due to the tremendous differences of the absorptivities between the UV and visible {dollar}\Lambda{dollar} max, the presence of trace levels of undefined quinones can present problems of identification either through isolation or direct LC/MS analysis.;Conjugated quinones give very strong molecular ions in the negative ion chemical ionization (NICI) mode. This is due to the fact that any quinone structure is a good candidate for electron capture. LC/MS equipped with a recently commercially available particle beam interface operating in the electron ionization and NICI modes with an on-line UV/Visible detector is a straightforward and powerful tool where structural information and compound characteristics can be obtained simultaneously. Increased sensitivity was achieved through some modifications of the commercially available system.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
