Chromatographic mass spectrometric determination of tetracycline antibiotics in water using a single-quadrupole mass analyzer

Introduction. Antibiotics and other pharmaceuticals are increasingly detected in surface groundwater, and drinking water, raising concerns about their potential adverse impacts on ecosystems and human health. Standard wastewater treatment methods often fail to effectively remove these compounds, particularly small organic molecules like tetracycline antibiotics, leading to their persistence in the environment. To address this issue, continuous monitoring and surveillance are necessary, including regular analysis of wastewater. Modern analytical methods, such as high-performance liquid chromatography coupled with mass spectrometric detection (HPLC-MS), allow detecting trace concentrations. This work presents a new method for qualitative and quantitative analysis using a quadrupole mass analyzer, which can serve as an alternative to tandem mass spectrometry.

Materials and methods. Tetracycline antibiotics (oxytetracycline, tetracycline, chlortetracycline, and doxycycline) in aquatic environments were detercted using selected ion monitoring (HPLC-MS) and selected reaction monitoring through tandem mass spectrometry (HPLC-MS/MS).

Results. There have been established chromatographic and mass spectrometric criteria for the identification of tetracyclines, determining key operating parameters for the quadrupole, such as selected ion scanning based on mass-to-charge ratio (m/z), signal registration time, and duration. The developed method for analyzing tetracyclines using a quadrupole mass analyzer demonstrates analytical characteristics comparable to tandem mass spectrometry based on a triple quadrupole mass analyzer. The method was validated on a quadrupole mass analyzer during the analysis of water samples from natural sources (drinking water, centralized water supply, and treated wastewater). In this analytical approach, the sample preparation process was simplified, allowing for the assessment of antibiotic content in samples without the need for labour-intensive solid-phase extraction and concentration, starting from 1 ng/ml and above (for various types of water mactrices).

Limitations. In this study, only the intact forms of tetracyclines were identified. Separate investigations into the detection of their chemical transformation products and epimerization were not conducted. The presented approach can be applied for analyzing wastewater and assessing the quality of its treatment, where the concentration of tetracycline antibiotics as micro-pollutants may exceed 10 ng/ml.

Conclusion. The proposed analytical method using a single quadrupole mass analyzer can serve as an alternative to the more expensive tandem mass spectrometer, both in terms of acquisition cost and maintenance. Key analytical characteristics that are important for environmental monitoring, such as selectivity and sensitivity, can be enhanced by optimizing the selected ion scanning mode. This was successfully demonstrated in the analysis of tetracyclines in aquatic environments. This approach could serve as a foundation for developing methodologies for detecting pharmaceutical compounds in environmental water samples using a quadrupole mass spectrometer.

Compliance with ethical standards. This study does not require the conclusion of a biomedical ethics committee or other documents.

Contribution:
Streletskiy A.V. – the concept and design of the study, collection and processing of material, statistical processing, writing a text;
Savostikova O.N. — the concept and design of the study, text writing, editing.
All authors are responsible for the integrity of all parts of the manuscript and approval of the manuscript final version.

Conflict of interest. The authors declare no conflict of interest.

Acknowledgment. The work was completed within the framework of the state task: reg. No 388-00099-23-02, No 123040500002-3.

Received: October 18, 2023 / Revised: July 24, 2024 / Accepted: October 2, 2024 / Published: January 31, 2025