The presence of micropollutants in South African aquatic systems has emerged as an
issue of public health concern. Micropollutants, such as endocrine disrupting
chemicals (EDCs) and antiretroviral compounds, have previously been detected in
surface water of South Africa. Micropollutants are often present in complex
environmental matrices at ultra-trace levels, complicating their detection.
In order to address shortcomings with traditional sample preparation methods, an inhouse
developed cheap, disposable polydimethylsiloxane (PDMS) sorptive sampler
was developed. The validity of the PDMS sampler was established by comparison with
a commercial stir bar sorptive sampler (SBSE). The sample introduction process into
a gas chromatograph (GC) was also simplified by using thermal desorption of a PDMS
sampler directly in the inlet liner of a GC. Direct thermal desorption was validated by
comparison to time-consuming thermal desorption using an expensive commercial
thermal desorption system (TDS).
With the aim of identifying a vast range of micropollutants in aquatic systems
comprehensive gas chromatography coupled to time-of-flight mass spectrometry
(GC×GC-TOFMS) was employed. The increased selectivity, sensitivity and larger
peak capacity of GC×GC-TOFMS allows the identification of more compounds in
complex matrices when compared to conventional GC-MS. An initial screening using
sorptive extraction techniques and GC×GC-TOFMS tentatively identified various
micropollutants, including EDCs, in surface water samples from the Rietvlei Nature
Reserve, Gauteng, South Africa.
Ultra-high pressure liquid chromatography coupled to mass spectrometry (UHPLCQTOFMS)
was used as a complementary analytical technique in conjunction with
GC×GC-TOFMS. Solid phase extraction (SPE) and large volume injection (LVI)
sample preparation steps preceded analysis by UHPLC-QTOFMS. SPE is more time
consuming and uses expensive solvents, however, adds selectivity to the sample
preparation step, by reducing possible matrix interferences which can be problematic
Matrix matched calibration curves were constructed to identify and quantify target
analytes in surface water samples. After validation of the analytical methods using chemometric approaches, these methods were employed to detect micropollutants in
surface water from a metropolitan area (Rietvlei Nature Reserve, Gauteng) and a rural
area (Albasini and Nandoni Dams, Limpopo Province) in South Africa. Limits of
detection (LOD) for the GC methods ranged from 1 to 98 pg/L for the PDMS loop and
1 to 190 pg/L for SBSE. The LODs for the LC methods ranged from 1.97 to 135 ng/L
for LVI and 73 pg/L to 57.3 ng/L for SPE.
The two simplified methods, the in-house developed PDMS loop with GC×GCTOFMS,
and LVI with UHPLC-QTOFMS, were used as complementary methods to
detect micropollutants, such as EDCs, in surface water. EDCs such as
pharmaceuticals, personal care products and pesticides, as well as the antiretroviral
compounds, efavirenz and nevirapine, were detected in surface water from South
Africa at concentration levels ranging from 0.16 ng/L to 227 ng/L.
As they have not been reported in literature before, experimental linear retention
indices are provided for the target analytes on the proprietary phase Rtx®-
CLPesticides II column. Lastly, the variance between different sampling sites was
investigated using principal component analysis (PCA). PCA revealed a difference in
micropollutant profile between sampling sites in the metropolitan and the rural area.