Anne Oldeide Haya, Frederik André Hansena
a Department of Pharmacy, University of Oslo, P.O Box 1068 Blindern, 0316 Oslo, Norway
Email: annehay@uio.no
Tetracyclines constitute a broad-spectrum class of antibiotics, particularly popular in livestock and animal farming due to their low cost, low toxicity and high availability [1]. While primarily used to treat bacterial infections, they are also employed as feed additives to promote weight gain and extend the storage period of meat. Tetracycline residues can enter the human body through livestock products such as milk, eggs, and meat, posing a public health risk by contributing to antibiotic resistance and triggering allergic reactions. Therefore, it is essential to monitor tetracycline levels in relevant food products to ensure they remain below the established minimum residue limits (MRL) [2].
A range of LC-MS methods have been developed for the determination of tetracyclines in food samples [1]. However, the sample preparation is often time consuming and involves multiple steps, require high amounts of organic solvent or extensive dilution due to the complexity of the matrix and polar character of the tetracyclines (log P < -2). Electromembrane extraction (EME) is a microextraction technique developed in 2006 [3] based on electrokinetic transfer of a target analyte from an aqueous sample, through a thin layer of organic solvent, and into an aqueous acceptor solution directly compatible with LC-MS/MS. For successful extraction, the analyte must be ionized, which is achieved by pH-adjustments of the sample and acceptor solutions. The electrical field, along with the organic solvent barrier between the sample and acceptor solution, ensures high selectivity and excellent clean-up. Only a few microliters of organic solvent are used per sample, aligning with green chemistry principles.
In this study, EME was used to extract four of the most common tetracyclines; oxytetracycline (OTC), tetracycline (TC), chlorotetracycline (CTC) and doxycycline (DC), from 2-fold diluted milk, egg white, honey, and plasma samples. The main purpose was to explore how different matrices affected the optimal extraction system. The resulting recoveries exceeded 66% for all compounds in all matrices, and high repeatability and low matrix effects were demonstrated.
References
1 Önal A. Overview on liquid chromatographic analysis of tetracycline residues in food matrices. Food Chem. 2011;127(1):197-203.
2 Pratiwi R, Azizah P, Nur Hasanah A, Asman S. Analytical strategies for monitoring tetracycline residues in various Samples: A focus on environmental and health implications. Microchem J. 2024;206:111408.
3 Pedersen-Bjergaard S, Rasmussen KE. Electrokinetic migration across artificial liquid membranes: New concept for rapid sample preparation of biological fluids. J Chromatogr A. 2006;1109(2):183-90.