Rapid and Robust Analysis Method for Quantifying Antidepressants and Major Metabolites in Human Serum by UHPLC-MS/MS

Significance of the Topic

The quantification of antidepressants and their primary metabolites in human serum is critical for therapeutic drug monitoring (TDM), ensuring optimal dosing, patient compliance and safety. Traditional HPLC coupled with diode-array detection often lacks sufficient sensitivity and selectivity, leading to potential false positives due to co-elution. The adoption of UHPLC-MS/MS addresses these limitations by offering enhanced analytical performance, shorter analysis times and reduced solvent usage, making it an attractive alternative for routine clinical laboratories.

Objectives and Study Overview

This study aimed to develop a rapid and robust UHPLC-MS/MS method capable of simultaneously quantifying a panel of commonly prescribed antidepressants and their major metabolites in human serum. A secondary goal was to compare the new method’s performance against established HPLC-DAD assays, evaluating correlation, selectivity and overall throughput.

Methodology

Sample Preparation:

• Off-line solid phase extraction (SPE) using C18 cartridges preconditioned with ammonia in acetonitrile and citrate buffer (pH 3.0).
• Sequential washes with water, acetonitrile and ammonia-in-acetonitrile to fractionate neutral/acidic compounds.
• Eluate concentration was minimized to maintain throughput; no isotopically labeled standards were required.

Chromatographic and MS Conditions:

• UHPLC column: Phenomenex Kinetex XB-C18 (100 × 2.1 mm, 2.6 µm), 30 °C.
• Mobile phases: 10 mM ammonium formate (A) and acetonitrile (B).
• Gradient: 10 % B at 0 min to 50 % B by 2.5–5 min, 75 % B at 6 min, return to 10 % B by 7.5 min; flow rate 0.4 mL/min.
• Injection volume: 5 µL.
• Detection: ESI positive mode, rapid polarity switching, MRM transitions for each compound, complemented by data-dependent acquisition of product ion spectra for identity confirmation.

Used Instrumentation

• Shimadzu Nexera UHPLC system with SIL-30AC autosampler.
• LCMS-8040 triple quadrupole mass spectrometer.
• Bakerbond Speedisk C18 Polar Plus SPE cartridges (50 mg/3 mL).

Main Results and Discussion

The UHPLC-MS/MS method successfully quantified 13 target analytes—including tricyclic antidepressants, SSRIs and their metabolites—with calibration linearity up to 600 µg/L. Comparison with HPLC-DAD across several hundred samples yielded correlation coefficients between 0.965 and 0.995, indicating excellent agreement. N-desmethylclozapine showed slight ion suppression, highlighting the importance of MRM optimization. Implementation of data-dependent acquisition allowed unambiguous confirmation of compound identity without the need for additional chromatographic verification.

Sample throughput improved significantly, with total analysis time per batch of 15 samples reduced from 40 to 15 minutes, thanks to simplified preparation and a 7.5-minute chromatographic cycle.

Benefits and Practical Applications

The optimized UHPLC-MS/MS workflow offers:

• Enhanced sensitivity and selectivity, lowering detection limits and reducing false positives.
• High throughput, enabling rapid turnaround in clinical settings.
• Cost savings through reduced solvent consumption and simplified sample prep.
• Multi-analyte capability, supporting comprehensive monitoring of patient medication regimens.

Future Trends and Opportunities

The integration of UHPLC-MS/MS into routine TDM is expected to accelerate, driven by automation and further miniaturization of sample preparation. Advances such as isotope dilution quantification, expanded panels covering emerging psychoactive substances and coupling with high-resolution MS for untargeted screening will broaden clinical applications. The adoption of AI-based data processing may further streamline data analysis and enhance diagnostic insights.

Conclusion

A rapid, robust UHPLC-MS/MS method has been validated for simultaneous quantification of antidepressants and major metabolites in human serum, demonstrating strong concordance with traditional HPLC-DAD while delivering superior speed, sensitivity and specificity. This approach is poised to replace conventional methods in clinical laboratories, improving TDM practices and patient care.

References

No external literature references were provided in the original document.