Simultaneous pressurized liquid extraction and clean-up for the determination of metabolites in complex environmental solid matrices

Parabens and pharmaceuticals are two of the most significant groups of pollutants of emerging concern. Nevertheless, in spite that their presence in the environment is well-known, to the date, there is scarce information about the presence of their metabolites that can be present at higher concentrations in the environment, be more toxic and be transformed into the parent compound. In this work, an analytical method has been developed and validated for the first-time simultaneous determination of metabolites of methyl- and propylparabens, caffeine, carbamazepine, diclofenac, ibuprofen and sulfamethoxazole and their parent compounds in soil, compost and digested sludge. Box-Behnken experimental design was applied for method optimisation due to the high number of experimental variables to optimize and the different physical-chemical properties of the target compounds. The method involves simultaneous sample extraction and clean-up by selective pressurized liquid extraction and analytical determination in a single run by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Good linearity, accuracy (mainly from 80 to 112%) and precision (<11%) was obtained. Method quantification limits were in the range from 0.12 to 14.4 ng g(-1) dry matter. The application of the method to soil, compost and digested sludge revealed that metabolites of parabens, carbamazepine, diclofenac and ibuprofen were at similar or higher concentrations than their parent compounds in digested sludge and the presence of metabolites of parabens, caffeine and carbamazepine in compost.