Clean-up of Organochlorine and Organophosphorus Pesticides from Vegetable Extracts Using ISOLUTE® SAX/PSA Columns

Importance of the Topic

Vegetable samples often contain low levels of non-polar organochlorine and organophosphorus pesticides alongside complex matrices of pigments and fats. Effective clean-up is critical to ensure accurate quantification, minimize matrix interferences, and reduce instrument maintenance.

Objectives and Study Overview

This application note describes a streamlined protocol for removing polar coextractives from acetonitrile extracts of vegetables using mixed-mode ISOLUTE SAX/PSA columns. It aims to deliver consistent recoveries for a broad range of pesticides and vegetable types, improving workflow efficiency.

Methodology

Sample preparation begins with homogenizing 20 g of vegetable tissue in 100 mL acetonitrile for 5 minutes, followed by filtration and concentration to 25 mL. Saturated NaCl solution is added, and the mixture is extracted twice with dichloromethane. The combined DCM layers are dried over anhydrous sodium sulfate, evaporated, and reconstituted in acetone:hexane (5:95, v/v; 2 mL).

The SPE clean-up uses ISOLUTE SAX/PSA 1 g/6 mL cartridges conditioned with acetone:hexane (5:95) over 10 mL. A 2 mL sample load at 1–2 mL/min is followed by elution with 10 mL of the same solvent. Final extracts are evaporated and adjusted to 4 mL in acetone:hexane (5:95) prior to analysis.

Used Instrumentation

Gas chromatography (GC) and gas chromatography–mass spectrometry (GC-MS) were employed for separation and detection of target pesticides.

Main Results and Discussion

The ISOLUTE SAX/PSA sorbent selectively retained polar interferences—such as pigments and fatty acids—while allowing non-polar pesticide analytes to elute with high recoveries. For particularly fatty matrices, an additional hexane (saturated with acetonitrile) wash further clarified extracts. Chromatograms exhibited reduced background noise and well-resolved pesticide peaks.

Benefits and Practical Applications

• Efficient removal of pigments and lipids with minimal solvent consumption.
• Broad applicability to various pesticide classes and vegetable matrices.
• Compatibility with routine GC and GC-MS protocols in environmental and food safety laboratories.

Future Trends and Potential Applications

Advances may include automated or miniaturized SPE formats, integration with multi-residue LC-MS/MS workflows for polar compounds, and development of field-deployable cartridges to enable on-site screening.

Conclusion

This protocol offers a robust, reproducible, and efficient clean-up strategy for non-polar pesticide residues in vegetable extracts, leading to enhanced analytical performance, reliability, and laboratory throughput.

References

• Biotage Application Note IST1027A.V.1 Clean-up of Organochlorine and Organophosphorus Pesticides from Vegetable Extracts, 2020.