EVALUATION OF NOVEL DISPERSIVE SPE AND PASS-THROUGH SPE OPTIONS FOR CLEANUP OF HIGH CHLOROPHYLL SAMPLES AFTER QUECHERS EXTRACTION

Significance of the Topic

Modern food safety laboratories rely on rapid and robust sample preparation workflows to handle large sample volumes. Leafy greens such as spinach contain high levels of chlorophyll and natural pigments that co-extract during QuEChERS workflows, leading to chromatographic interference, instrument contamination, and compromised MS detection.

Objectives and Study Overview

The study aimed to compare traditional dispersive SPE (dSPE) using graphitized carbon black (GCB) with a pass-through SPE approach employing Oasis PRiME HLB cartridges. Key goals included:

• Assessing pigment removal efficiency by UPLC-PDA monitoring.
• Evaluating pesticide recoveries for planar compounds (cyprodinil, chlorothalonil, thiabendazole) by GC-MS/MS and UPLC-MS/MS.

Methodology and Instrumentation

Sample Preparation and Cleanup:

• QuEChERS extraction: 15 g homogenized spinach, 1% acetic acid in ACN, AOAC salts, centrifugation.
• dSPE variants: 150 mg Na2SO4, 50 mg C18, 50 mg PSA plus either 10 mg or 50 mg GCB per mL extract.
• Pass-through SPE: Oasis PRiME HLB vac-style or plus-type cartridges; minimal conditioning; 0.8 mL waste, 1.5 mL collect.

Analytical Platforms:

• UPLC-PDA: ACQUITY I-Class FTN, Cortecs UPLC T3 column, 450 nm detection for pigments.
• APGC-MS/MS: Agilent 7890/Waters Xevo TQ-S, Restek Rxi-5ms column, MRM in API+ mode for GC pesticides.
• UPLC-MS/MS: ACQUITY UPLC I-Class, BEH C18 column, ESI+ MRM for LC-amenable pesticides.

Main Results and Discussion

All cleanup protocols substantially reduced chlorophyll and carotenoids. Key findings:

• Pass-through Oasis PRiME HLB removed >99 % of chlorophyll and >95 % of lutein, outperforming 10 mg GCB dSPE.
• dSPE with 50 mg GCB eliminated all pigments but induced significant losses of planar pesticides.
• Oasis PRiME HLB and dSPE with 10 mg GCB preserved high recoveries (>90 %) of cyprodinil, chlorothalonil, thiabendazole.
• No performance differences were noted among various plus-type PRiME HLB cartridge formats.

Benefits and Practical Application

The pass-through SPE approach offers:

• Streamlined workflow with no conditioning steps.
• Consistent pigment removal without pesticide losses.
• Compatibility with syringe or vacuum manifolds for flexible lab setups.

Future Trends and Possibilities

Emerging developments may include:

• Integration of disposable pass-through cartridges in automated platforms.
• Extension of PRiME HLB cleanup to diverse food matrices with high pigment loads.
• Miniaturized SPE formats for resource-constrained or field-based testing.

Conclusion

Pass-through SPE using Oasis PRiME HLB cartridges represents an effective cleanup strategy for high-pigment QuEChERS extracts, combining superior pigment removal with excellent recovery of challenging planar pesticides. This method enhances throughput and instrument longevity while maintaining analytical integrity.

References

• Young M.S.; Shia J.C. Evaluation of novel dispersive SPE and pass-through SPE options for cleanup of high chlorophyll samples after QuEChERS extraction. Waters Corporation Poster, 2017.