Hlengilizwe Nyoni, Bhekie B Mamba and Titus AM Msagati
Preliminary use of performance reference compounds (PRC) spiked into the silicone-membrane/γ-Fe2O3 sampler for in situ calibration has been demonstrated to improve the quantitative nature of water concentration estimates. Hydrophobic polycyclic aromatic hydrocarbons (PAHs), though they occur at significant levels in the environment, were used as PRC because of their relatively high fugacity from the silicone membrane and evidence of their isotropic exchange kinetics. In situ calibrations of silicone-membrane/γ-Fe2O3 sampler spiked with 16 PAHs and the resulting time weighted average (TWA) concentration estimates were compared with similar values of SPE extracts from grab samples. Calibration studies were successfully done and variable environmental conditions (e.g. effects of hydrodynamics and temperature) were found to affect their elimination rates from silicone-membrane/γ-Fe2O3 sampler. A significant increase of elimination rates with change of hydrodynamic conditions from static to turbulent was observed for all compounds under investigation. The technique has also been successfully applied to the detection of freshwater cyanobacterial toxins such as microcystins and cylindrospermopsin.
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