Determination of Tetracyclines Residues in the Gulf of Gdańsk (Southern Baltic Sea) Sediments Using a Tandem Solid-Phase Extraction with Liquid Chromatography Coupled with Tandem Mass Spectrometry

Abstract

Pharmaceuticals are biologically active and relatively persistent substances which have been recently recognized as a continuing threat to the aquatic environment. Numerous adverse effects may arise for aquatic non-target organisms from the presence of pharmaceutical residues. One of the main pharmaceutical contaminants are antibiotics which are in the environment in considerable concentrations and can have negative biological effects to marine microorganisms. Despite of this, the knowledge on antibiotics occurrence, behaviour and fate in the Baltic Sea is very limited. This study presents the preliminary results on tetracycline and oxytetracycline residues occurrence in the sediments collected from the Gulf of Gdańsk (southern Baltic Sea). Among the antibiotics, tetracyclines are one of the most popular class used for human and animal therapy and for animal breeding. The method for tetracyclines residues determination was optimized, using two types of Baltic sediments (sandy and muddy) spiked at nine concentration levels (from 1 to 1,000 ng g⁻¹ d.w.) to achieve the best validation parameters. Acetonitrile and EDTA-McIlvaine extraction buffer solution (pH 4) (1:1) for extraction and tandem SPE technique with Discovery SAX and Oasis HLB cartridges for extracts clean-up were applied. Quantitative and qualitative determination of analysed antibiotics was performed with the use of liquid chromatography tandem mass spectrometry (LC-MS/MS) with electrospray ionization source in the positive mode. The recoveries for target antibiotics ranged from 78.8 to 131.1 % for tetracycline and 75.5–114.8 % for oxytetracycline. The LOD values ranged from 1.5 to 3.5 ng g⁻¹ d.w. for tetracycline and from 1.2 to 2.2 ng g⁻¹ d.w. for oxytetracycline. The developed method was applied in the determination of tetracyclines in six sediments collected in 2012 during r/v “Oceania” cruises. Oxytetracycline was identified in four of analyzed samples at concentrations from 21 to 625 ng g⁻¹ d.w. Tetracycline was determined only in one sediment sample collected close to WWTP “Gdańsk Wschód” outlet (13.8 ng g⁻¹ d.w.). None of the target compounds was identified in the accumulation area—the Gdańsk Deep.