Analysis of Pesticides in Vegetables Using the Agilent 1260 Infinity Analytical SFC System with Triple Quadrupole MS Detection

Importance of the topic

Pesticide residues in vegetables pose significant health risks and are strictly regulated. Efficient analytical workflows are essential to ensure compliance with legal limits and protect consumer safety. Supercritical fluid chromatography (SFC) coupled with triple quadrupole MS offers rapid separations and reduced matrix effects compared to conventional HPLC.

Objectives and Study Overview

This study aimed to optimize SFC separation conditions for 16 common pesticide compounds in a complex rocket (arugula) extract. Four different methanol gradient profiles were evaluated to identify parameters that minimize matrix suppression and achieve reliable quantification at low parts-per-billion levels.

Methodology and Instrumentation

Sample Preparation:

• QuEChERS extraction of 10 g homogenized rocket using acetonitrile, buffered salts, and dispersive SPE cleanup (PSA, graphitized carbon black, MgSO₄).
• Final extract acidified with formic acid to stabilize analytes.

SFC Conditions:

• Column: Agilent ZORBAX NH₂ (4.6 × 150 mm, 5 µm).
• Mobile phase: CO₂ with methanol modifier; flow 3 mL/min; column temperature 40 °C; backpressure regulator at 120 bar, 60 °C.
• Four gradients tested, varying steepness of methanol increase from 2 % to cleaning step at 50 % modifier.

MS Detection:

• Agilent 6460 Triple Quadrupole MS in positive electrospray mode.
• MRM transitions optimized for each pesticide; make-up flow of acetonitrile with 0.2 % formic acid.

Instrumentation Configuration:

• Agilent 1260 Infinity Analytical SFC System with splitter assembly feeding the 6460 MS.
• Modules: SFC control, binary pump, autosampler, degasser, thermostatted column compartment, diode array detector, isocratic pump.

Main Results and Discussion

Gradient Impact:

• Fast gradient (gradient 1) exhibited significant matrix suppression for most pesticides in rocket extract.
• Shallower gradients (gradients 2–4) improved separation from co-extracted matrix components, enhancing signal intensities.
• Gradient 4 (moderate slope to 12 % methanol in 8 min) delivered the best overall performance, reducing suppression and increasing recoveries.

Recovery and Sensitivity:

• Solvent calibration at 10, 20, 100 ppb showed linearity (R² > 0.999) for all analytes.
• Apparent recoveries in spiked matrix ranged 70–120 % for 14 compounds; atrazine and terbuthylazine improved to acceptable levels after 1:10 dilution.
• LODs between 0.03–3 ppb and LOQs between 0.1–10 ppb; all met the 10 ppb target.

Benefits and Practical Applications of the method

• Rapid separations (7 min run) increase sample throughput.
• Orthogonal selectivity of SFC reduces matrix interference.
• Direct injection of QuEChERS extracts in organic solvent streamlines workflow.
• Sensitivity meets regulatory requirements for pesticide monitoring in produce.

Future Trends and Possibilities

• Integration of SFC with high-resolution MS to expand screening capabilities for non-target contaminants.
• Automation and miniaturization to further increase throughput and reduce solvent consumption.
• Application to a wider range of complex food matrices and environmental samples.
• Green analytical chemistry initiatives leveraging CO₂-based mobile phases for sustainability.

Conclusion

Optimizing the methanol gradient profile in SFC is critical for minimizing matrix suppression and achieving robust quantification of pesticide residues in vegetables. The selected shallow gradient delivers fast, sensitive, and accurate analysis, demonstrating the strength of SFC–MS in routine food safety testing.

References

1. Regulation (EC) No 396/2005 on maximum residue levels of pesticides in food and feed.
2. Anastassiades M., Lehotay S. J., Štajnbaher D., Schenk F. J. (2003) Fast and Easy Multiresidue Method. J. AOAC Int. 86(2):412–431.
3. Naegele E., Glauner T. (2014) Optimizing SFC/MS for Pesticide Analysis. Agilent Technologies Application Note 5991-5256EN.
4. European Commission SANCO/12571/2013 Guidance on analytical quality control for pesticide residues.