Liquid chromatography quadrupole time‐of‐flight mass spectrometry identification and determination of tri‐ and hexaaryl chloro imidazoles in sewage sludge

The identification and further quantification of 2‐chloro‐triarylimidazole (o‐Cl‐TAI) and its dimer (o‐DCl‐HABI) in sludge from a sewage treatment plant (STP) is reported for the first time. Liquid chromatography (LC) quadrupole time‐of‐flight (QTOF) mass spectrometry (MS) was used as analytical technique during screening and determination steps. Pollutants were identified following a post‐run search strategy, applying the chlorine mass filter, and characterized by their accurate MS and product ion scan spectra. Finally, their identities were confirmed with authentic standards. The species (o‐Cl‐TAI) has been rated as potentially genotoxic and carcinogenic for mice and rats. Effects of sample preparation in the stability and the extraction efficiency of both compounds are discussed. Under final conditions, they were extracted from freeze‐dried samples (0.5 g of sludge or biosolids dispersed with 2 g of C₁₈ and packed into a polypropylene syringe) with 20 ml of methanol, which also flowed through a clean‐up layer of Florisil and PSA sorbents (0.5 g each). This method attained quantitative extraction yields and limits of quantification between 4 and 10 ng/g. The pollutants o‐Cl‐TAI and o‐DCl‐HABI were ubiquitous in sludge and biosolids obtained in consecutive years from the investigated STP. Their concentrations varied from 0.02 to more than 13 μg/g (freeze‐dried sample). Copyright © 2016 John Wiley & Sons, Ltd.