A NOVEL SORBENT FOR PASS-THROUGH SPE CLEANUP: A SIMPLE, QUICK, AND EFFECTIVE ALTERNATIVE FOR REMOVAL OF LIPIDS AND CHLOROPHYLL FROM QUECHERS EXTRACTS

Importance of the Topic

In pesticide residue analysis of complex food matrices such as avocado and spinach, co-extracted lipids, phospholipids and chlorophyll cause chromatographic interferences, instrument contamination and signal suppression. A streamlined cleanup approach is critical to maintain instrument uptime, ensure accurate quantitation and support high throughput in routine food safety laboratories.

Objectives and Study Overview

This study evaluated a novel pass-through SPE sorbent (Oasis PRiME HLB) as a simple, rapid and effective alternative to conventional multi-step dispersive SPE (dSPE) for removal of fats, phospholipids and chlorophyll from QuEChERS extracts of avocado (high-lipid matrix) and spinach (high-chlorophyll matrix). The performance of Oasis PRiME HLB was compared against two dSPE formats containing C18, PSA and varying levels of graphitized carbon black (GCB).

Methodology and Instrumentation

Sample Preparation:

• Avocado: 5 g homogenate mixed with 5 mL water, 15 mL 1:99 acetic acid/ACN, shaken 1 min, centrifuged.
• Spinach: 15 g homogenate with 15 mL 1:99 acetic acid/ACN, shaken 1 min, centrifuged.

Cleanup Approaches:

• Pass-through SPE: Oasis PRiME HLB cartridge (3 cc, 150 mg) without pre-conditioning; 0.8 mL extract discarded, 1.5 mL passed and collected.
• dSPE A: 150 mg Na₂SO₄, 50 mg C18, 50 mg PSA, 50 mg GCB per 2 mL spinach extract.
• dSPE B: same as A but 10 mg GCB per 1 mL extract.

Analytical Instrumentation:

• UPLC-MS/MS: Waters ACQUITY UPLC I-Class with BEH C18 column (100 × 2.1 mm, 1.7 µm), Xevo TQ-S micro ESI+ MRM.
• UPLC-PDA: ACQUITY I-Class FTN, Cortecs UPLC T3 column, monitored at 450 nm for pigment tracking.
• APGC-MS/MS: Agilent 7890 GC with Restek Rxi-5ms column, Xevo TQ-S micro API+ MRM.

Main Results and Discussion

Removal Efficiency:

• Oasis PRiME HLB removed >95 % of fats and phospholipids from avocado extracts.
• It achieved >99 % removal of chlorophyll and >95 % removal of lutein from spinach extracts.
• dSPE with 50 mg GCB removed pigments but caused >20 % losses of planar pesticides (e.g., folpet, captan).
• dSPE with 10 mg GCB was less effective at pigment removal.

Pesticide Recovery:

• Pass-through SPE preserved high recoveries for both LC-amenable and GC-amenable pesticides, including planar chemistries.
• APGC-MS/MS demonstrated improved chromatographic response and minimal signal suppression after Oasis PRiME cleanup.

Benefits and Practical Applications

Oasis PRiME HLB pass-through cleanup offers:

• A one-step protocol requiring no sorbent conditioning.
• Short processing time (<5 min per sample).
• Minimal solvent use and reduced waste.
• Broad compatibility with UPLC-MS/MS and GC-MS workflows.
• Robust removal of matrix interferences while protecting analyte integrity.

Future Trends and Potential Uses

Opportunities to expand this approach include:

• Adapting cartridge formats and sorbent loading to other complex matrices (e.g., nuts, leafy greens).
• Automating pass-through SPE in 96-well or on-line formats for ultra-high throughput.
• Developing tailored sorbents for polar interferences or novel pesticide chemistries.
• Integrating with advanced mass spectrometry platforms for comprehensive residue screening.

Conclusion

Oasis PRiME HLB provides a simple, rapid and effective cleanup solution for QuEChERS extracts of high-lipid and high-chlorophyll food matrices. It outperforms conventional dSPE by achieving superior pigment and lipid removal without compromising pesticide recoveries, thereby streamlining sample preparation and enhancing analytical robustness in food safety testing laboratories.