Please use this identifier to cite or link to this item: http://hdl.handle.net/10321/555
Title: Optimisation of HPLC-based methods for the separation and detection of herbicide glyphosate and its major metabolite in water
Authors: Madikizela, Lawrence Mzukisi 
Issue Date: 2010
Abstract: Water storage dams play an important part in the collection and purification of water destined
for human consumption. However, the nutrient rich silt in these dams promotes rapid growth
of aquatic plants which tend to block out light and air. Glyphosate is universally used as the
effective non-selective herbicide for the control of aquatic plants in rivers and dams.
Invariably there is residual glyphosate present in water after spraying of dams and rivers with
glyphosate herbicide. The amount of residual glyphosate is difficult to determine on account
of high solubility of glyphosate in water. Thus a method of sample preparation and a sensitive
HPLC method for the detection of trace amounts of glyphosate and its major metabolite
aminomethylphosphonic acid (AMPA) in water is required. A crucial step in sample
preparation is pre-column derivitization of glyphosate with 9-fluorenylmethyl chloroformate
(FMOC-Cl).
For sample pretreatment, water samples were derivatized with FMOC-Cl at pH 9, extracted
with ethyl acetate and sample clean-up was carried out by passing a sample through the SPE
cartridge. For SPE, recovery studies were done to choose a suitable cartridge for glyphosate
and AMPA analysis. The following cartridges were compared, namely, C18, Oasis HLB and
Oasis MAX SPE cartridges. Best recoveries (101% for glyphosate and 90% for AMPA) were
obtained using 500 mg of C18 solid-phase extraction cartridge. The eluent from SPE cartridge
was injected into HPLC column. Three types of separation columns (namely; C18 column,
silica based amino column and polymeric amino column) were compared for the separation
of glyphosate and AMPA. The best separation of glyphosate and AMPA in water samples
was achieved using a polymeric amino column and a mobile phase at pH 10 which contained
a mixture of acetonitrile and 0.05 M phosphate buffer (pH 10) 55:45, (v/v) respectively.
The method was validated by spiking tap water , deionized water and river water at a level of
100 μg/l. Recoveries were in the range of 77% -111% for both analytes. The method was also
used in determining the levels of glyphosate and AMPA in environmental samples. This
method gave detection limits of 3.2 μg/l and 0.23 μg/l for glyphosate and AMPA
respectively. The limits of quantification obtained for this method were 10.5 μg/l and 3.2 μg/l
for glyphosate and AMPA respectively.
Description: Dissertation submitted in partial compliance with the requirements for the Masters Degree in Technology, 2010.
URI: http://hdl.handle.net/10321/555
Appears in Collections:Theses and dissertations (Applied Sciences)

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