LC-MS/MS Method for the Determination of Enalapril and Enalaprilat from Human Plasma Using SOLA

Significance of the Topic

A rapid and reliable method to quantify enalapril and its active metabolite enalaprilat in human plasma is critical for pharmacokinetic studies, therapeutic drug monitoring, and bioequivalence assessments. High-throughput laboratories require sample preparation workflows that combine sensitivity, reproducibility, and minimal solvent usage to maintain cost-effectiveness and data quality.

Objectives and Study Overview

This application note describes the development of a streamlined LC-MS/MS workflow using Thermo Scientific SOLA solid-phase extraction (SPE) cartridges and Hypersil GOLD reversed-phase chromatography. The goals were to achieve:

• Efficient extraction of enalapril and enalaprilat from human plasma
• Fast chromatographic cycle time of 1 minute
• Linear quantitation between 1–100 ng/mL with high recovery and precision

Methodology and Instrumentation

• Sample Preparation: 200 µL plasma spiked with analytes and benazepril as an internal standard, acidified, and processed on 10 mg SOLA SPE cartridges. Conditioning (methanol, water), loading under gravity, washing with 0.1 % formic acid, elution with 2 % ammonia in methanol, drying, and reconstitution in 90:10 water:methanol.
• Chromatography: Hypersil GOLD 1.9 µm, 50 × 2.1 mm column at 70 °C. Mobile phases A (water + 0.1 % formic acid) and B (acetonitrile + 0.1 % formic acid). Gradient from 10 % to 100 % B in 1 min, flow 0.6 mL/min, injection volume 2.5 µL.
• Mass Spectrometry: Thermo Scientific TSQ Vantage triple quadrupole with HESI in positive mode. Selected reaction monitoring transitions:
  
  • Enalapril 377.25 > 234.19 (CE 16 eV)
  • Enalaprilat 349.22 > 206.15 (CE 17 eV)
  • Benazepril (IS) 425.26 > 351.23 (CE 19 eV)

Main Results and Discussion

The method demonstrated excellent linearity over 1–100 ng/mL with correlation coefficients of 0.9986 (enalapril) and 0.9974 (enalaprilat). Precision at 50 ng/mL QC levels was better than 6.6 % CV for both analytes. Mean recoveries were 81 % for enalapril, 85 % for enalaprilat, and 87 % for benazepril, with negligible carryover. Representative chromatograms showed sharp, symmetric peaks within a one-minute analysis window.

Benefits and Practical Applications

• Reduced solvent consumption and faster drying times due to efficient SPE design
• High analytical throughput with a 1-minute cycle time
• Robust quantitation in complex matrices suitable for clinical and bioanalytical laboratories
• Cost savings through lower solvent use and minimal rework from improved reproducibility

Future Trends and Opportunities

Advances may include automation of SPE workflows, integration with microflow or nano-LC platforms to further reduce sample and solvent usage, and expansion of this approach to other prodrug–metabolite pairs. Emerging SPE materials and high-resolution mass spectrometry could enhance sensitivity and selectivity for low-abundance biomarkers in pharmacokinetic and clinical research.

Conclusion

The combination of Thermo Scientific SOLA SPE cartridges and Hypersil GOLD columns enables a simple, rapid, and high-performance LC-MS/MS method for enalapril and enalaprilat in human plasma. The workflow delivers excellent recovery, linearity, precision, and throughput, meeting the demands of high-throughput bioanalytical laboratories.

References

No external literature references were provided in the source document.