Analysis of Degradation Products of Doxycycline in Solution Exposed to Light and Elevated Temperatures Using the Agilent 1200 Infinity Series High Dynamic Range Diode Array Detector Impurity Analyzer System

Significance of the Topic

Accurate assessment of antibiotic stability is essential for ensuring drug safety and efficacy. Doxycycline, like other tetracyclines, is prone to epimerization and degradation when exposed to light and heat. Monitoring trace-level impurities supports shelf-life determination, quality control and regulatory compliance in pharmaceutical manufacturing.

Objectives and Study Overview

This application study aimed to track the degradation of doxycycline solutions under accelerated conditions. Samples were exposed to daylight at 40 °C for up to 5.5 days. The key goal was to detect and quantify emerging degradation products and to evaluate the sensitivity and dynamic range of the Agilent 1200 Infinity Series HDR-DAD Impurity Analyzer System.

Methodology and Instrumentation

Sample preparation involved dissolving 20 mg of doxycycline in water/acetonitrile (1:2) and injecting 1 µL (13.33 µg doxycycline). Chromatographic separation used an Agilent ZORBAX Eclipse XDB-C8 column (3 × 100 mm, 3.5 µm) at 40 °C with a gradient of water, acetonitrile and 1 % TFA. Mobile phase flow was 0.8 mL/min. Detection employed the Agilent 1200 Infinity HDR-DAD Impurity Analyzer, combining a 60 mm and a 3.7 mm flow cell, with wavelengths of 230, 280 and 350 nm. Data were acquired and processed using Agilent OpenLAB CDS ChemStation.

Main Results and Discussion

The HDR-DAD system achieved a peak-to-peak noise level as low as 0.013 mAU, enabling reliable detection of impurities with heights below 0.2 mAU. Over the 5.5 day exposure, doxycycline content declined by approximately 5.3 %. Thirteen degradation products were identified, with some present at time zero and others appearing after 17 hours. Impurity levels exhibited distinct growth profiles, illustrating the kinetics of decomposition under stress conditions.

Contributions and Practical Applications

The study demonstrates that high-dynamic-range diode array detection allows simultaneous quantification of the parent drug and trace impurities in a single run. This capability enhances routine stability testing workflows, supporting pharmaceutical QC laboratories in meeting stringent regulatory requirements without additional sample preparation.

Future Trends and Potential Applications

Advances in HDR-DAD technology may be coupled with high-resolution mass spectrometry for structural identification of degradation products. Automated data processing and real-time trend analysis will further streamline stability protocols. Expanding this approach to other labile drug classes can improve comprehensive impurity profiling.

Conclusion

The Agilent 1200 Infinity HDR-DAD Impurity Analyzer System offers low noise, wide dynamic range and multi-wavelength detection for sensitive monitoring of doxycycline degradation. The method supports accurate stability assessment and impurity quantification, enhancing pharmaceutical development and quality assurance.

References

• R. Injac, V. Djordjevic-Milic, B. Srdjenovic, Thermostability Testing and Degradation Profiles of Doxycycline in Bulk, Tablets, and Capsules by HPLC, Journal of Chromatographic Science, Vol. 45, October 2007.
• L.A. Mitscher, The Chemistry of the Tetracycline Antibiotics, Medical Research Series, Vol. 9, Marcel Dekker, New York, 1978, p. 123.
• Y. Liang, M.B. Denton, R.B. Bates, Stability Studies of Tetracycline in Methanol Solution, Journal of Chromatography A, 827, 45–55, 1998.
• HPLC and Pharmaceutical Stability Studies, Microbac Laboratories, Inc., 2011.