Automatic searching and evaluation of priority and emerging contaminants in wastewater and river water by stir bar sorptive extraction followed by comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry

A new analytical method based on stir bar sorptive extraction (SBSE), followed by comprehensive two-dimensional gas chromatography (GCxGC-TOF-MS), has been developed for the automatic searching and evaluation of nonpolar or semipolar contaminants in wastewater and river water. The target compounds selected were 13 personal care products (PCPs), 15 polycyclic aromatic hydrocarbons (PAHs) and 27 pesticides. Excellent results have been obtained in terms of separation efficiency and also in terms of compound identification. Exceptional method detection limits were achieved applying the optimized method, at or below 1 ng/L for most of the compounds in real samples. The reliable confirmation of analyte identity was possible at this low concentration level, even for typically troublesome compounds such as the PAHs. The other validation parameters were good. In addition to obtaining analytical information such as identification and quantification of target analytes, it is also possible to screen for nontarget compounds or unknowns. New contaminants have been identified in the wastewater effluents and river water samples, such as cholesterol and its degradation products, pharmaceuticals, industrial products, other pesticides, and PCPs. The multidimensional information generated by the instrument can also be used by the researchers for contrasting samples and identifying, much more easily, the major differences between samples. We have used this feature to propose studies of comparison between the fingerprinting of different water samples, such as the contamination variation along a river affected by the discharge of urban wastewaters and also the contamination variation over a period of time in the effluent. Results show that the most frequently detected contaminants (and the contaminants detected at higher concentrations) were the PCPs. The musk fragrances galaxolide and tonalid were the most concentrated compounds in the samples. The pesticides and PAHs were present at much lower concentration than PCPs.