A New Kind of Amide free Polymer for Simplified, Improved SPE

Importance of the Topic

Efficient sample cleanup is essential in bioanalysis to reduce matrix interferences, minimize ion suppression, and achieve reliable quantitation of pharmaceutical compounds in complex biological fluids. Advances in SPE chemistries address the need for improved selectivity and streamlined workflows in LC–MS assays.

Study Objectives and Overview

This study evaluates a novel amide-free, water-wettable polymer phase (Bond Elut Plexa) designed to exclude proteins and lipophilic impurities while retaining analytes at its hydrophobic core. The performance of the new sorbent is compared with conventional polymeric SPE materials in terms of recovery, matrix cleanliness, and ion suppression for two model beta-blockers (metoprolol and propranolol) extracted from human plasma.

Methodology

1. Sample Preparation: 100 µL human plasma diluted 1 : 3 with 200 mM NH4Ac (pH 10), spiked with analytes or processed blank.
2. SPE Procedure: Conditioning with methanol and water, sample loading, washing (95 : 5 water/methanol), elution with methanol (2 × 100 µL), evaporation, and reconstitution in mobile phase.
3. Chromatography: Agilent Pursuit C18 (3 µm, 2.0 × 50 mm), gradient elution (80 : 20 to 20 : 80 of 0.1% formic acid/methanol), 4.5 min total run at 10 µL injection.
4. Mass Spectrometry: Triple-quadrupole MS with Argon collision gas; MRM transitions 268.2 → 116.0 (metoprolol), 260.0 → 116.0 (propranolol).

Used Instrumentation

• Bond Elut Plexa SPE plates
• Agilent LC system with Pursuit C18 column
• Agilent triple-quadrupole mass spectrometer

Main Results and Discussion

• Calibration curves for both drugs showed excellent linearity (R2 > 0.999) from 1 to 1000 ng/mL with precision <5% RSD and accuracy within ±10%.
• Absolute recoveries exceeded 90% when compared to mobile-phase standards, outperforming traditional polymer SPE (53–92% vs 81–98%).
• The hydrophilic pore gradient effectively prevented protein and lipid binding, yielding cleaner extracts and reducing ion suppression in ESI source, as confirmed by overlapped ion suppression chromatograms.

Practical Benefits

• Simplified method development using a general protocol for diverse analytes.
• Enhanced sensitivity and reproducibility in LC–MS bioanalysis.
• Time savings through reduced sample pretreatment steps and robust cleanup.

Future Trends and Applications

The incorporation of amide-free, polarity-graded sorbents is expected to expand to other drug classes and biomolecules, supporting high-throughput workflows in pharmaceutical and clinical research. Further innovations may integrate automated platforms and novel surface chemistries for targeted extractions.

Conclusion

Bond Elut Plexa offers a significant advancement in SPE technology by combining hydrophilic surface characteristics with core analyte retention, delivering high recoveries, superior matrix removal, and improved LC–MS performance for bioanalytical applications.

Reference

• Agilent Technologies, Application Note 5990-8756EN, July 2011.