Streamlined Method for Pesticide Residues in High-Lipid Food Samples Using QuEChERS Extraction, LipiFiltr® Cleanup, and UHPLC–MS/MS Analysis

The easy to use, new LipiFiltr® push-through purification cartridge was designed to remove lipids from acetonitrile extracts. This application will outline the performance benefits achieved using the new LipiFiltr® cartridges in applications involving multiclass, multiresidue analysis for pesticides in complex, high fat samples. Samples are extracted using a standard QuEChERS procedure and an aliquot of the supernatant is simply pushed through the LipiFiltr® purification cartridge using a disposable syringe. The purified extract is collected in an autosampler vial and analyzed by LC–MS/MS. The ability to obtain significantly cleaner extracts, the ease of use, and the time and cost savings make the new LipiFiltr® push-through cartridges an attractive cleanup option for laboratories conducting pesticide residue analysis in complex fatty samples.

Procedure Sample Extraction

(a) Weigh 5–10g of homogenized sample into a 50-mL centrifuge tube. Add 5 mL reagent water if necessary.

(b) Add 10 mL acetonitrile and internal standards.

(c) Shake or vortex samples for 5 min at 1000 strokes/min.

(d) Add ECQUEU7-MP packet to each sample and shake for 1 additional min at 1000 strokes/min.

(e) Centrifuge at ≥3000 rcf for 15 min.

(f) Attach LipiFiltr® push-through cartridge to disposable syringe.

(g) Take 1.5 mL of supernatant into syringe barrel. Attach the plunger and gently push the sample through the LipiFiltr® cartridge into an autosampler vial.

Instrumental

LC–MS/MS: Shimadzu Nexera X2 coupled with Shimadzu LCMS-8050

UHPLC column: 100 × 2.1 mm, 1.8-µm Selectra® Aqueous C18

Guard column: 10 × 2.1 mm, 1.8-µm Selectra® Aqueous C18

Injection volume: 2 µL

Mobile phase A: H2O containing 0.1% formic acid + 5 mM ammonium formate

Mobile phase B: Methanol containing 0.1% formic acid + 5 mM ammonium formate

Column flow rate: 0.45 mL/min

Results

The performance of the LipiFiltr® push-thru cartridges to remove fatty matrix was evaluated gravimetrically. The gravimetric analysis was done by collecting 2 mL of sample before and after clean-up in pre-weighed test tubes and heating them to dryness at 110 °C.

Conclusion

This application note demonstrates the performance benefits achieved using the new LipiFiltr® cartridge in applications involving multiclass, multiresidue analysis for a wide range of pesticides (n = 189) in complex, high fat samples. Individualized recoveries obtained for each pesticide in a variety of matrices, such as avocado, olives, beef, and swordfish, can be found at unitedchem.com

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