Application of solid phase extraction (SPE) method in determining polycyclic aromatic hydrocarbons (PAHs) in river water samples

Trace levels of PAH pollutants are difficult to detect in water samples due to their low solubility. During this study, SPE method was used to improve the detection of the PAH analytes. A Visipre SPE vacuum manifolds sample preparation method was used to clean-up the river water samples before analysis. Twelve samples were simultaneously extracted via the unit. This method is generally faster and significantly increases sample throughput, while decreasing sample preparation hands-on time which is common for methods such as liquid-liquid extraction. An Agilent 1100 Series High Performance Liquid Chromatography (HPLC) was used to analyze trace levels of PAH compounds in river water samples before and after SPE treatment. Chromatograms of samples which were analyzed before treatment with the SPE method were simple, lacked details and could be mistaken as uncontaminated. However, after sample treatment, new peaks appeared which were well separated and relatively easier to identify when compared against chromatograms of PAHs standard mixtures that were prepared under the same experimental conditions. Samples had peaks with the following retention times (tR): Ace (tR = 7.186 m), Phe (tR = 8.440 m), Anth (tR = 8.951 m) and Fluo (tR = 10.375 mins) from the Vaal river water samples; Naph (tR = 6.514 mins), Ace (tR = 7.180 ms), Phe (tR = 8.431 m), Anth (tR = 8.845 m) and Fluo (tR = 10.367 m) from the Klip river water samples and Ace (tR = 7.134 m), Phe (tR = 8.437 m), Anth (tR = 8.947 m), Fluo (tR= 10.370 m), BbFl (tR = 18.628 m), InPy (tR =27.404 m) from the Barrage river water samples. The SPE sample preparation method was successful in purifying and improving the detectability of PAH analytes.