• Gas chromatographic electron capture negative ionization mass spectrometric (GC/ECNI/MS) determination of unique fluorinated compounds in the sediments of Lake Ontario and the effect of high-boiling alcohols (as injection solvents) on chromatographic behaviour of polycyclic aromatic hydrocarbons in gas chromatography

      Zielinski-Lawrence, Rosalie Krystyna.; Department of Chemistry (Brock University, 2009-01-28)
      Part I - Fluorinated Compounds A method has been developed for the extraction, concentration, and determination of two unique fluorinated compounds from the sediments of Lake Ontario. These compounds originated from a common industrial landfill, and have been carried to Lake Ontario by the Niagara River. Sediment samples from the Mississauga basin of Lake Ontario have been evaluated for these compounds and a depositional trend was established. The sediments were extracted by accelerated solvent extraction (ASE) and then underwent clean-up, fractionation, solvent exchange, and were concentrated by reduction under nitrogen gas. The concentrated extracts were analyzed by gas chromatography - electron capture negative ionization - mass spectrometry. The depositional profile determined here is reflective of the operation of the landfill and shows that these compounds are still found at concentrations well above background levels. These increased levels have been attributed to physical disturbances of previously deposited contaminated sediments, and probable continued leaching from the dumpsite. Part II - Polycyclic Aromatic Hydrocarbons Gas chromatography/mass spectrometry is the most common method for the determination of polycyclic aromatic hydrocarbons (PAHs) from various matrices. Mass discrimination of high-boiling compounds in gas chromatographic methods is well known. The use of high-boiling injection solvents shows substantial increase in the response of late-eluting peaks. These solvents have an increased efficiently in the transfer of solutes from the injector to the analytical column. The effect of I-butanol, I-pentanol, cyclopentanol, I-hexanol, toluene and n-octane, as injection solvents, was studied. Higher-boiling solvents yield increased response for all PAHs. I -Hexanol is the best solvent, in terms of P AH response, but in this solvent P AHs were more susceptible to chromatographic problems such as peak splitting and tailing. Toluene was found to be the most forgiving solvent in terms of peak symmetry and response. It offered the smallest discrepancies in response, and symmetry over a wide range of initial column temperatures.
    • Mass spectral studies of some pentafluorophenyl derivatives of group V /|nby Andrew Tanner Rake. -- 260 St. Catharines, Ont. : [s. n.],

      Rake, Andrew Tanner.; Department of Chemistry (Brock University, 1970-07-09)
      The mass spectra of compounds of t he series (C6F5 )3-n MP~ (n = 1,2,3, M = P and As ), (C6F5>3Sb, Ph) Sb and (C6F5 )2SbPh have been studied in detail and the important modes of fragmentation were e1ucidated, a ided by metastable ions. Various trends attributed to the central atom and or the . substituent groups have been noted and, where applicable, compared to recent studies on related phenyl and pentafluorophenyl compounds of groups IV and V. The mass spectra of fluorine containing organometallic compounds exhibit characteristic migrations of fluorine to t he central atom, giving an increasing abundance of MF+, MF2+' and RMF+ (R = Ph or C6F5) ions on descending the group_ The mass spectra of pentafluorophenyl , antimony, and arsenic compounds show a greater fragmentation of the aromatic ring than those of phosphorus. The mixed phenyl pentafluorophenyl derivatives show a characteristic pattern depending on the number of phenyl grm.lps present but show t he general characteristics of both the tris(phenyl) and tris(pentafluorophenyl) compounds. The diphenyl pentafluorophenyl der ivatives show the loss of biphenyl ion as the most import ant step, the los s of phenyl t o give the i on PhMC6F5 + being of secondary importance. The ,bis(pentafluorophenyl) phenyl derivatives fragment primarily by loss of PhC6F5 to give C6F5M+ ions, the abundance of t hese increasing r apidly from phosphorus to arsenic. This species then, exhibits a characteristic fragmentation observed in the tris(penta- fluorophenyl ) compounds. However, the abundance of (C6F5)2M+ species in these compounds i s small. I ons of the type C6H4MC6F4 + and tetrafluorobiphenylene ions C6H4C6F4 + also are observed on substitution of a phenyl group for a penta- fluorophenyl group. The fully fluorinated species (C6F4)2M+ is not observed, although octafluorobiphenylene ions , (C6F4)2+' are evident in several spectra . The appearance potentials of the major ions were obtatned from the ionisation efficiency curves. Attempts were made to correlate these to the effect of the central atom in substituent groups, but the large errors involved prevented the reaching of quantitative conclusions, although it would appear that the electron is removed from the ligand in the ionisation of t he parent molecule .