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Organotin compounds: their analyses and effect on model biomembranes

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Title: Organotin compounds: their analyses and effect on model biomembranes
Author: Nwata, Basil Ugwunna
Degree Doctor of Philosophy - PhD
Program Chemistry
Copyright Date: 1994
Abstract: Studies involving the analyses of organotin compounds in marine organisms of British Columbia, and the effect of organotin compounds on the permeability of model biological membranes are presented in this thesis. Analysis of organotin compounds by gas chromatography-selected ion monitoring mass spectrometry (GC-MS SIM) affords a very specific technique for the identification and quantitation of organotin compounds, by using the peculiar isotope pattern for tin compounds. This methodology is therefore able to distinguish organotin compounds from other compounds that may co-elute with them from the gas chromatograph. Although some British Columbian locations such as Hastings Arm, Alice Arm, etc showed no organotin contamination, the major organotin pollutants found for some coastal areas such as Denman Island, Dundas Island, etc were tributyltin and dibutyltin species. The butyltin body content for Blue mussels in the contaminated areas range from 14.4 to 37.3 ng/g (wet wt as Sn) for tributyltin and 6.7 to 67.3 ng/g (wet wt as Sn) for dibutyltin species. Dicyclohexyltin levels of 3.5 ng/g and 21.3 ng/g (wet wt as Sn) were found only at Wreck Beach Vancouver, and Anyox respectively. The effect of organotin compounds on egg phosphatidyicholine (EPC) liposomes or organotin-EPC liposomes, were established by studing the efflux of a probe compound; dimethylarsinic acid (DMA) trapped inside these liposomes, by using 1H NMR spectroscopy. The probe compound at pH 7.4 exists as two chemical When the organotin compounds were added externally to the EPC liposomes, tributyltin chloride caused an increased permeability of the liposomes, which was linearly dependent on the concentration of the externally added tributyltin chloride solution. Monobutyltin trichioride decreased the permeability coefficient of DMAH to the EPC liposomes from 1.7 x 10-8 to 4 x i0 cm/s, while trimethyltin cation facilitated the efflux of DMK from the liposomes. For TBT-EPC liposomes formed by a mixture of tributyltin chloride and EPC, the efflux of DMA from these liposomes was facilitated by the tributyltin cation only if the liposomes were not in contact with externally added tributyltin chloride solution. When in contact with externally added tributyltin chloride, the ability of the tributyltin cation to act as carrier for DMK was lost. The activation energy for the passive efflux of DMAH from TBT-EPC liposomes varied from 52.3 to 64.4 kJ/mol depending on the tributyltin content of the liposome. For the monobutyltin trichloride-EPC liposomes (MBT-EPC), the monobutyltin cation did not exhibit any ability to act as carrier for DMA irrespective of whether it was externally added to the liposomes or not. The DMAH species permeate by passive diffusion with activation energy of 106.8 to 121.5 kJ/mol. A modified batch hydride generation-graphite furnace atomic absorption spectrophotometric method (HG-GFAAS) is described for total tin determination. In this method, tin hydride was adsorbed and pre-concentrated on graphite furnace tubes pre-coated with palladium or sodium tungstate matrix modifiers, prior to their atomization in the graphite furnace. species; DMAH and DMK which are capable of diffusing from these liposomes.
URI: http://hdl.handle.net/2429/7067
Series/Report no. UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/]

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