Robust Extraction, Separation and Quantitation of Structural Isomer Steroids From Human Plasma by SPE with LC-MS/MS Detection

Significance of the Topic

The accurate quantitation of steroid structural isomers in human plasma is essential for clinical research, as overlapping mass spectra can lead to misinterpretation of hormone levels. Robust sample preparation and chromatographic separation are needed to ensure reliable detection and measurement of these biologically important analytes.

Objectives and Study Overview

This study aimed to develop and validate a solid-phase extraction (SPE) combined with LC–MS/MS method for the separation, identification, and quantitation of 12 structurally related steroids in human plasma. Two LC gradient approaches were compared to optimize the resolution of isobaric and closely eluting compounds across a wide dynamic range.

Methodology

Sample preparation involved protein precipitation with zinc sulfate followed by SPE cleanup on a SOLAµ HRP plate. Two chromatographic methods were employed on an Accucore biphenyl column: a rapid acetonitrile gradient for routine steroid panels (4.2 min run) and an extended methanol gradient (12 min run) for enhanced resolution of isomeric pairs. Calibration curves ranged from 50 to 50000 pg/mL, with QC samples at 500 and 5000 pg/mL.

Instrumentation Used

• Thermo Scientific Vanquish Horizon UHPLC system
• Thermo Scientific TSQ Quantiva Triple-Stage Quadrupole MS
• Thermo Scientific Dionex Chromeleon 7.2.8 Chromatography Data System

Key Results and Discussion

The biphenyl column demonstrated superior selectivity and peak capacity compared to C18 chemistry. Peak widths were reduced (0.058 min vs. 0.066 min) and resolution between critical isomer pairs increased markedly (e.g., 21-deoxycortisol vs. 11-deoxycortisol resolution improved from 1.9 to 7.9). Retention time stability was excellent (<0.1% RSD over 25 injections), and method linearity covered three orders of magnitude (R² > 0.99). Accuracy ranged from 95 to 107% and precision remained below 8% across QC levels.

Benefits and Practical Applications

• Accurate differentiation and quantitation of steroid isomers in complex plasma matrices
• High-throughput analysis with fast run times for routine laboratories
• Robust retention time stability supporting longitudinal clinical studies
• Wide dynamic range enabling low-level quantitation down to 50 pg/mL

Future Trends and Opportunities

Advancements may include integration of novel stationary phases for even greater selectivity, ultra-high-throughput UHPLC workflows, automation of sample processing, and coupling with high-resolution mass spectrometry for steroid metabolomics. Expanded panels and software-driven data analysis will further enhance clinical and research applications.

Conclusion

The validated SPE–LC–MS/MS method using an Accucore biphenyl column offers an effective solution for separating challenging steroid isomers in plasma. It delivers excellent accuracy, precision, and retention time stability across a broad concentration range, making it well suited for clinical research and diagnostic laboratories.

References

• Thermo Fisher Scientific application note, 2018