DETERMINATION OF PHARMACEUTICALS’ RESIDUES IN WASTEWATER OBTAINED WITH AN OPTIMIZED LC-FTICR MS METHOD

The presence of pharmacologically active molecules or their derivatives found in wastewater is a problem of wide interest (1,2). Pharmaceutical compounds (PhCs) and their metabolites, even if present in the order of µg/L and ng/L, can affect the bioconcentration factor, and then be subject to bioaccumulation and biomagnification showing toxic effects for both flora and fauna and mankind. The high resolution liquid chromatography mass spectrometry (LC-MS) coupled to tandem mass spectrometry MS/MS has gained popularity in recent decades thanks to its versatility, specificity and selectivity, finding application as the preferred method for the analysis of PhCs in complex matrices such as waste and/or discharge water. (3,4) Most methods developed in the past have focused on specific therapeutic classes, such as antibiotics for their potential resistance to biotic degradation. In this work we focus on the development of an analytical multi-residual method by using LC-FT/ICR-MS and IRMPD for a particular class of pharmaceuticals chosen according to the 10 mostly diffused and consumed products in the Mediterranean area (4-8). A solid phase extraction from spiked tap water followed by LC-FTICR MS determination has been proposed for the simultaneous analysis of these pharmaceuticals as in Figure 1: (peak 1) metformin hydrochloride (exact m/z 130.10872), (peak 2) amoxicillin (exact m/z 366.11182), (peak 3) caffeine (exact m/z 195.08765), (peak 4) erythromycin (exact m/z 734.46852), (peak 5) clarithromycin (exact m/z 748.48417), (peak 6) carbamazepine (exact m/z 237.10224), (peak 7) naproxen (exact m/z 231.10157), (peak 8) diclofenac sodium (exact m/z 294.00941), (peak 9) ibuprofen (exact m/z 205.12340), (10) aspirin (exact m/z 181.04954). In order to ascertain the identity of all chromatographic peaks, the measurements and interpretation of IRMPD-FTICR data was accomplished. All precursor ions were photon irradiated for 200 ms at 100% laser power by a 20 W continuous CO2 laser source at a wavelength of 10.6 μm. The method optimized was applied to samples collected from influent and effluent from a Wastewater Treatment Plants (WWTP) in order to assess the efficiency of the plant for removing this kind of recalcitrant compounds. Among the PhCs considered in this study, only carbamazepine and clarithromycin were found in the effluent of the WWTP.