INSTRUMENTAL DEVELOPMENT AND APPLICATION OF MS/MS TO SOLVENT REFINED COAL ANALYSIS
Abstract
Computerized data acquisition and scanning methods have been implemented on a magnetic mass spectrometer of reversed geometry. These improvements have facilitated routine computer controlled acquisition of MS/MS (MIKES) spectra resulting from collision-induced dissociation (CID) occurring in a collision cell located between the magnet and electric sector in the second field free region (FF2) of the mass spectrometer. Software has been developed which allows a new type of MS/MS scan. This scan, termed a neutral loss scan, detects all components in a complex mixture which undergo FF2 CID with loss of a neutral fragment of specified mass. These scans are performed using a computer controlled nonlinear linked scan of the electric and magnetic sector fields. Neutral loss scans have been used to screen unknown mixtures for certain functional groups. The isomer specificity of the high energy (keV) CID process has been investigated for a series of substituted aromatic and polynuclear aromatic hydrocarbons (PNAs) commonly found in coal liquefaction products. Results indicate that isobaric compounds generally produce distinguishable MS/MS spectra. Isomeric compounds can often be differentiated on the basis of their MS/MS spectra, but certain PNA isomer pairs have been observed to yield very similar MS/MS spectra with the current methodology. Negative chemical ionization (NCI) in conjunction with charge inversion MS/MS has been found to provide useful spectra from compounds which do not give negative fragment ions upon CID. Examples are given for several unsubstituted PNAs. The quantification of fluoranthene in SRC and the detection of a previously unreported homologous series containing alkyl-substituted benzenethiol subunits in SRC-II has also been accomplished using NCI charge inversion MS/MS. A source has been designed to permit laser desorption (LD) of involatile organics. This combined LD/CI/EI source is described and results are given for the LDMS/MS analysis of silver-cationized sucrose.
Degree
Ph.D.
Subject Area
Analytical chemistry
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