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A solid phase microextraction/gas chromatography method for estimating the concentrations of chlorpyrifos, endosulphan-alpha, edosulphan-beta and endosulphan sulphate in water
Author(s)
Adam, Hassan Ali
Date Issued
2003
Type
Thesis
Publisher
Peninsula Technikon
Abstract
The monitoring of pesticide contamination in surface and groundwater is an essential
aspect of an assessment of the potential environmental and health impacts of
widespread pesticide use. Previous research in three Western Cape farming areas found
consistent (37% to 69% of samples) pesticide contamination of rural water sources.
However, despite the need, monitoring of pesticides in water is not done due to lack of
analytical capacity and the cost of analysis in South Africa. The Solid Phase
Microextraction (SPME) sampling method has been developed over the last decade as
a replacement for solvent-based analyte extraction procedures. The method utilizes a
short, thin, solid rod of fused silica coated with an absorbent polymer. The fibre is
exposed to the pesticide contaminated water sample under vigorous agitation. The
pesticide is absorbed into the polymer coating; the mass absorbed depends on the
partition coefficient of the pesticide between the sample phase and the polymeric
coating, the exposure time and factors such as agitation rate, the diffusivity of the
analyte in water and the polymeric coating, and the volume and thickness of the
coating. After absorption, the fibre is directly inserted into the Gas Chromatograph
(GC) injection port for analysis.
For extraction from a stirred solution a fibre will have a boundary region where the
solution moves slowly near the fibre surface and faster further away until the analyte is
practically perfectly mixed in the bulk solution by convection. The boundary region
may be modelled as a layer of stationary solution surrounded by perfectly mixed
solution.
aspect of an assessment of the potential environmental and health impacts of
widespread pesticide use. Previous research in three Western Cape farming areas found
consistent (37% to 69% of samples) pesticide contamination of rural water sources.
However, despite the need, monitoring of pesticides in water is not done due to lack of
analytical capacity and the cost of analysis in South Africa. The Solid Phase
Microextraction (SPME) sampling method has been developed over the last decade as
a replacement for solvent-based analyte extraction procedures. The method utilizes a
short, thin, solid rod of fused silica coated with an absorbent polymer. The fibre is
exposed to the pesticide contaminated water sample under vigorous agitation. The
pesticide is absorbed into the polymer coating; the mass absorbed depends on the
partition coefficient of the pesticide between the sample phase and the polymeric
coating, the exposure time and factors such as agitation rate, the diffusivity of the
analyte in water and the polymeric coating, and the volume and thickness of the
coating. After absorption, the fibre is directly inserted into the Gas Chromatograph
(GC) injection port for analysis.
For extraction from a stirred solution a fibre will have a boundary region where the
solution moves slowly near the fibre surface and faster further away until the analyte is
practically perfectly mixed in the bulk solution by convection. The boundary region
may be modelled as a layer of stationary solution surrounded by perfectly mixed
solution.
Additional information
Thesis (MTech (Chemical Engineering))--Peninsula Technikon, Cape Town, 2003
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