Matrix solid-phase dispersion followed by liquid chromatography tandem mass spectrometry for the determination of selective ciclooxygenase-2 inhibitors in sewage sludge samples

• An extraction method based on matrix solid-phase dispersion (MSPD) was optimized.
• The determination of COXIBs residues in STPs sludge was done using LC-QTOF-MS.
• Two of targeted COXIBs have been systematically found in real samples of sludge.
• The screening capabilities of the LC-QTOF-MS system were demonstrated.

A straightforward single-step extraction method based on matrix solid-phase dispersion (MSPD), followed by high-performance liquid chromatography with hybrid quadrupole time of flight mass spectrometry (LC–QTOF-MS), was developed and optimized to determine five non-steroidal anti-inflammatory drugs (Valdecoxib, Etoricoxib, Parecoxib, Celecoxib and 2,5-Dimethylcelecoxib) in sewage sludge samples. The influence of different operational parameters on the extraction efficiency a well as in the matrix effects of the produced extracts was evaluated in detail. Under final working conditions, freeze dried samples (0.2 g) were first soaked with 100 μL of aqueous potassium hydroxide solution (60%, w/v), mixed with 1 g of anhydrous sodium sulfate and dispersed with 1 g of Florisil. This blend was transferred to the top of a polypropylene column cartridge containing 3 g of silica. Analytes were recovered using 15 mL of hexane/acetone (1:2, v/v) mixture. The extracts were concentrated by evaporation and reconstituted with 1 mL of methanol/water (1:1, v/v), filtered and injected in the LC system. Quantification limits from 0.005 and 0.05 ng g−1 and absolute recoveries between 86 and 105% were achieved. Results indicated the presence of two of the targeted COXIBs in real samples of sewage sludge, the highest average concentration (22 ng g−1) corresponding to celecoxib. Moreover, the screening capabilities of the LC–QTOF-MS system demonstrated that the developed MSPD extraction procedure might be useful for the selective extraction of some other pharmaceuticals (e.g. amiodarone and their metabolite N-desethylamiodarone, miconazole, clotrimazole and ketoprofen) from sludge samples.