Methodologies for the analysis of pesticides and pharmaceuticals in sediments and plant tissue

Eco-technologies that utilize natural processes involving wetland vegetation, soil and their associated microbial assemblages are increasingly used for the removal of contaminants of emerging concern (CECs) from polluted water. However, information on removal processes in these systems is not always available, possibly due to the lack of simple and robust methodologies for the analysis of CECs in complex matrices such as sediment and plant tissue. The aim of the present study was to use a simple and fast procedure based on ultrasonic extraction (USE) and reduced clean-up procedures to analyse 8 pesticides and 9 pharmaceuticals by high-performance liquid chromatography (HPLC) coupled with a diode array detector. The established methods demonstrated suitable sensitivity and reliability, and proved fit-for-purpose in quantifying multiple classes of pesticides and pharmaceuticals. For sediments, extraction with methanol/acetone (95:5, v/v) followed by a simple evaporation to dryness and redissolution (water:methanol 50:50) provided acceptable recovery (50-101%) and RSD < 14%. The complex matrix of plant samples posed specific problems resulting in individualized approaches for pesticides and pharmaceuticals under the final optimized conditions. Pesticides were extracted with n-hexane followed by saponification (KOH), pH adjustment and solid-phase extraction, while pharmaceuticals were extracted with methanol:acetone (95:5), supernatant cleaned with activated carbon, evaporated to dryness and redissolved (water:methanol 50:50) prior to HPLC injection. The final method characteristics, with a few exceptions, showed acceptable recovery (>64%) with RSD < 22% determined using different types of wetland plants. The methodology has been successfully applied in different studies on the fate of emerging contaminants in water treatment eco-technology systems.