Doxepin in Human Plasma Using SOLA and Accucore Core Enhanced Technology HPLC Column

Importance of the topic

Tricyclic antidepressants such as doxepin require precise quantification in biological matrices to support therapeutic monitoring, pharmacokinetic studies and clinical diagnostics. High-throughput bioanalysis demands efficient sample preparation and rapid chromatographic separation to ensure reliable data while minimizing solvent use and processing time.

Objectives and study overview

This work describes the development and validation of a fast, sensitive method for the determination of doxepin in human plasma using novel SOLA solid-phase extraction cartridges combined with Accucore core-enhanced HPLC columns. The primary goals were to achieve high recovery, low matrix interference and rapid analysis suitable for routine bioanalytical workflows.

Methodology and instrumentation

Sample preparation utilized SPE with SOLA 10 mg cartridges under optimized conditioning, loading, washing and elution steps to isolate doxepin and the internal standard protriptyline from plasma. Chromatographic separation was performed on a 2.6 µm Accucore C18 column (50×2.1 mm) at 40 °C with a gradient of water and acetonitrile, both containing 0.1 % formic acid, at 0.4 mL/min. Detection was carried out using a UV detector at 245 nm. Data acquisition and integration used ChromQuest software.

Main results and discussion

The SPE procedure provided clean extracts with reduced phospholipid background and high reproducibility. Doxepin and internal standard peaks were resolved within two minutes, with a short gradient wash and re-equilibration enabling rapid throughput. Single-point calibration with protriptyline yielded an average recovery of 113 % and precision of 5.6 % RSD across five replicates. The low backpressure of the core-shell column facilitated stable performance and minimal re-equilibration time on instruments with standard dwell volumes.

Benefits and practical applications

• High extraction consistency and reduced sample cleanup time
• Rapid chromatographic run (≤2 min) enabling high throughput analysis
• Enhanced sensitivity due to cleaner extracts and efficient column technology
• Reduced solvent consumption and lower operational costs
• Applicability to clinical pharmacokinetic studies and therapeutic drug monitoring

Future trends and opportunities

The combination of advanced SPE media and core-shell column technology is poised to expand into multiplexed assays for multiple drug analytes, further supporting high-volume clinical and pharmaceutical workflows. Integration with mass spectrometric detection could improve sensitivity and selectivity for low-level bioanalysis. Continued miniaturization and automation of sample preparation will drive further efficiencies in bioanalytical laboratories.

Conclusion

The presented method leveraging SOLA cartridges and Accucore core-enhanced HPLC columns achieves fast, reliable quantification of doxepin in human plasma. It delivers robust recovery, precision and throughput advantages critical for modern bioanalytical applications.

Used instrumentation

• SOLA 10 mg/1 mL SPE cartridges
• Thermo Scientific Finnpipettes and HyperSep glass block manifold
• Accucore C18 2.6 µm (50×2.1 mm) HPLC column
• Thermo Scientific HPLC system with UV detection at 245 nm
• Thermo Scientific ChromQuest version 5.0 software

References

• Aspey S. et al. Application Note ANCCSSOLADPIN, Thermo Fisher Scientific, 2011.