A pressurised hot water extraction and liquid chromatography–high resolution mass spectrometry method to determine polar benzotriazole, benzothiazole and benzenesulfonamide derivates in sewage sludge

• A pressurised hot water extraction method was developed for the analysis of sludge samples.
• Simultaneous determination of benzotriazoles, benzothiazoles and benzenesulfonamides.
• Recoveries were above 80% and matrix effect was below 20% for most of the compounds.
• Different clean-up strategies were tested to reduce the matrix effect.
• Method provides limits of detection and quantification below ng g−1 (d.w.).

Benzothiazole, benzotriazole and benzenesulfonamide derivates are well-known aquatic contaminants, although very few studies have been published about their occurrence in sewage sludge samples. In this paper, a pressurised hot water extraction (PHWE) method has been developed for the simultaneous determination of these families of compounds. The compounds were determined by LC–Orbitrap–HRMS and several clean-up strategies such as in-cell PHWE and solid-phase extraction (SPE) were tested to reduce the high matrix effect that occurs when sludge samples are analysed. Absolute recoveries using the whole method were above 80% and the matrix effect was under −20% for most of the compounds studied. Repeatability and reproducibility were usually under 10% (%RSD, 50 and 250 ng g−1 (d.w.), n = 5), while LODs and LOQs were between 0.25 and 25 ng g−1 (d.w.) and 0.5 and 50 ng g−1 (d.w.), respectively. The PHWE/SPE/LC–HRMS method developed was used to analyse several sludge samples collected from five sewage treatment plants (STPs) in Catalonia that use different sewage treatments. The most frequently determined compounds were benzotriazole derivates and the most abundant compound found was 2-hydroxybenzothiazole.