DETERMINATION OF METRONIDAZOLE RESIDUES IN WATER AND SEDIMENT SAMPLES

Metronidazole (MET) is an antibacterial and antiprotozoal drug widely used in animal husbandry, including fish farming. It belongs to a class of antibiotics known as nitroimidazoles. MET has a minimum inhibitory concentration of 1 mu g. mL(-1) against S. vortens in vitro, with the recommended dose in ornamental fish equal 10 mg per 1 g fish food. For the treatment of fish food, 2.5 g kg(-1) or 4 mg L-1 is recommended. However, in 1998, due to its environmental side effects, cytotoxicity and genotoxicity European Council Regulation 613/98/EEC announced that any residue of this drug found in food-producing animals or in products intended for human consumption must be considered as a violation of the EU regulation. Addition of metronidazole to animal food is also banned in the USA. In surface waters, this substance may be accumulated in sediments and/or undergo abiotic (photodegradation and/or hydrolysis) and biotic degradation. Investigations, of its fate and distribution in aquatic and edaphic environments are still very few. One of the main reasons is limited number of methods adopted for determination of metronidazole in aquatic and sediment samples. In this work, development of new analytical methods for determination of MET in surface waters and sediments samples using HPLC-UV and LC-MS techniques has been carried out. Isolation and enrichment of MET from surface waters was performed using solid phase extraction procedure. Several conditions such as type of SPE cartridges, type of washing solvents, type of eluents were tested. Application of Strata X-C cartridge with elution of MET using a mixture of 28% NH4OH and acetonitrile (5:95, v/v) was found as optimal. Next, isolation of MET from sediments samples was optimized. Two extraction methods: QuECheRS and shaking with 0.1 M HCI solution were tested. The obtained extracts were purified by SPE. It was found that the second procedure allowed to achieve higher recovery of MET (92.8%). Next, validation of whole analytical procedures was performed. Such parameters as: linearity, sensitivity, repeatability and reproducibility of the proposed methods for determination of metronidazole in waters and sediments were established. In the end, the proposed methods were applied for analysis of surface waters and sediments collected from rivers in Northern Poland.