Efficient and Clean Extraction of a Multi-Drug Panel with Oasis PRiME MCX for Clinical Research

Importance of the Topic

Efficient isolation of multiple drug classes from plasma is critical in clinical research and bioanalysis. Mixed-mode solid-phase extraction (SPE) combines selective ion exchange and hydrophobic interactions to isolate basic analytes, but traditional protocols often struggle to remove endogenous phospholipids that cause matrix effects in LC–MS/MS. The development of simplified SPE workflows that maintain high recovery while minimizing phospholipid contamination addresses a key challenge in quantitative bioanalysis.

Objectives and Overview of the Study

This work evaluates a novel sorbent, Oasis PRiME MCX, in comparison with Oasis MCX and Oasis PRiME HLB for extracting a panel of basic drugs including opioids, benzodiazepines, stimulants, and others. The goal is to compare recovery, matrix effects, and residual phospholipid levels across simple 3- or 4-step SPE protocols, demonstrating the balance between ease of use, cleanliness, and reproducibility for clinical research applications.

Methodology and Sample Preparation

Human plasma was fortified with target analytes at relevant concentrations and processed using four SPE workflows:

• Oasis PRiME HLB: reversed-phase SPE with aqueous dilution, wash, and elution with varying ACN/MeOH mixtures.
• Oasis MCX: mixed-mode strong cation exchange with acidified plasma, dual washes (formic acid and MeOH), and basic elution.
• PRiME MCX 4-step: MCX-based extraction with ammonium formate wash improving phospholipid removal.
• PRiME MCX 3-step: simplified protocol combining sample dilution and MeOH wash, eliminating one aqueous wash.

All extracts were diluted with a water/ACN/formic acid solution prior to UPLC–MS/MS analysis.

Instrumentation

• Oasis PRiME HLB, Oasis MCX, and Oasis PRiME MCX 96-well µElution plates
• ACQUITY UPLC I-Class system (FTN) with ACQUITY BEH C18 1.7 µm, 2.1 × 100 mm column (40 °C)
• Xevo TQ-S micro triple quadrupole mass spectrometer (ESI positive)
• MassLynx v4.1 and TargetLynx XS software

Main Results and Discussion

The reversed-phase PRiME HLB method yielded low recovery (<20–50%) for many polar, ionizable drugs despite clean extracts at low MeOH elution. Traditional MCX achieved good recoveries but left high levels of residual phospholipids, leading to matrix effects.

The PRiME MCX protocols matched MCX recoveries (>80% for most analytes) while reducing phospholipid content by 95–98% relative to conventional MCX. Residual phospholipid levels using PRiME MCX were comparable to or lower than those obtained with PRiME HLB eluted under optimized conditions. Matrix effects were maintained below 20% for the majority of compounds in the PRiME MCX workflows.

Benefits and Practical Applications

• Combines high selectivity for basic drugs with efficient phospholipid removal
• Simplified 3- or 4-step protocols reduce preparation time and solvent use
• Improved reproducibility and lower matrix effects support robust quantitation in clinical and toxicological studies
• Compatible with high-throughput 96-well formats for large sample batches

Future Trends and Applications

Further work may extend PRiME MCX to other analyte classes and biological matrices, integrate with automated SPE platforms, and refine solvent compositions for specific drug panels. Advances in sorbent design and SPE automation will continue to streamline sample preparation and improve data quality in regulated and research laboratories.

Conclusion

Oasis PRiME MCX offers a streamlined mixed-mode SPE approach that achieves high recoveries of basic drugs and exceptional phospholipid clearance in simple 3- and 4-step protocols. This balances analytical performance with operational efficiency, making it well suited for clinical research workflows that demand both cleanliness and throughput.

References

1. Chambers E., Wagrowski-Diehl D. M., Lu Z., Mazzeo J. R. Systematic and comprehensive strategy for reducing matrix effects in LC-MS/MS analyses. Journal of Chromatography B, 2007, 852(1–2):22–34.
2. Danaceau J. P., Chambers E. Analysis of plasma 17-hydroxyprogesterone, androstenedione and cortisol using a novel solid-phase extraction sorbent, Oasis PRiME HLB, for UPLC-MS/MS analysis in clinical research. Waters Application Note, 2015, 720005416EN.
3. Zhang X., Danaceau J. P., Chambers E. Improvements in recovery, reproducibility, and matrix effects with Oasis PRiME HLB, a novel solid phase extraction sorbent. Waters Application Note, 2015, 720005495EN.
4. Chemaxon. Chemicalize, 2017, https://chemicalize.com.