OPTIMIZED PASS-THROUGH SPE CLEANUP FOR LC-MS/MS MULTI-RESIDUE VETERINARY DRUG ANALYSIS

Importance of the Topic

Multi-residue screening of veterinary drug residues in food matrices is essential to ensure consumer safety and regulatory compliance. Traditional residue analysis required targeted, multi-step cleanup and enrichment, which was laborious and time-consuming. Advances in LC-MS/MS sensitivity now allow streamlined sample preparation while maintaining broad analyte coverage and low detection limits.

Objectives and Study Overview

This study aimed to develop and optimize a simple pass-through solid-phase extraction (SPE) cleanup using Oasis PRiME HLB cartridges for multi-residue veterinary drug analysis in beef muscle. Key goals included:

• Maximizing recovery of 39 veterinary drugs spanning a range of polarities (Log P 3–6).
• Efficient removal of lipids and phospholipids from acetonitrile-based extracts.
• Defining optimal cartridge loading and elution volumes for high throughput workflows.

Methods and Instrumentation

Sample Preparation and Cleanup

• Extract 2 g beef muscle with 15 mL 85:15 acetonitrile/water (0.2 % formic acid). Centrifuge and dilute the supernatant 1:1 with acetonitrile to reach ~85 % organic.
• Pass 2 mL of diluted extract through a 3 cc, 150 mg Oasis PRiME HLB cartridge to waste, discarding early eluent containing polar interferences.
• Apply 3 mL of diluted extract and collect the eluate for analysis, avoiding breakthrough of phospholipids and fats (which elute after >5 mL).

Analytical Instrumentation

• LC system: ACQUITY UPLC H-Class with BEH 2.1 × 100 mm column, 40 °C.
• Mobile phase A: 0.1 % formic acid in water; B: 0.1 % formic acid in methanol; injection volume 7 µL.
• MS detection: Waters Xevo TQ-S micro in MRM mode; ESI− for selected analytes, ESI+ for others.

Main Results and Discussion

Pass-through SPE behaves like frontal chromatography. Early elution (first 2 mL) contains polar analytes and matrix co-extractives and must be discarded. Collection of the next 3 mL yields peak concentrations of moderately non-polar to non-polar drugs. Trials with test compounds (bithionol, niclosamide, oxyphenbutazone) showed maximum recovery in fractions 2–4, while phospholipids and fats broke through only after 6 mL. Recovery data for 39 drugs demonstrated consistent yields (10–100 µg/kg spike) with low variability, confirming the method’s robustness.

Benefits and Practical Application

The optimized pass-through cleanup offers:

• Rapid sample preparation without multi-step elution or solvent exchanges.
• Effective removal of lipids and phospholipids, reducing matrix effects.
• Broad analyte coverage across a range of polarities.
• Flexibility for manual syringe or vacuum manifold operation.
• High throughput suitability for routine QA/QC and regulatory monitoring labs.

Future Trends and Opportunities

Further developments may include:

• Automation and integration with robotic SPE platforms for increased throughput.
• Extension of the cleanup approach to other complex matrices (dairy, fish, eggs).
• Exploration of novel sorbent chemistries for enhanced selectivity.
• Coupling with high-resolution MS for non-target and suspect screening.
• Miniaturization of SPE formats to reduce solvent use and waste.

Conclusion

The optimized Oasis PRiME HLB pass-through SPE cleanup provides a streamlined, reliable protocol for multi-residue veterinary drug analysis in beef muscle. By discarding an initial fraction and collecting a defined eluate, the method achieves excellent analyte recovery and efficient removal of interfering lipids and phospholipids, enabling high sensitivity LC-MS/MS monitoring in routine food safety laboratories.

Reference

Young MS, Blaze M, Shia JC. Optimized Pass-Through SPE Cleanup for LC-MS/MS Multi-Residue Veterinary Drug Analysis. Waters Corporation, 2019.