Representative, Tw o-gram Incurred Food Samples Using Mini-QuEChERS, Cryomilling and GC/MS/MS Analysis with a High Efficiency Ion Source

Importance of the Topic

The demand for sensitive, cost-effective multi-residue pesticide analysis in foods drives continuous innovation in sample preparation. Miniaturized QuEChERS combined with cryomilling reduces sample size and solvent use while maintaining the stringent performance required by regulatory and quality control laboratories.

Objectives and Overview of the Study

This study evaluates a 2 g mini-QuEChERS protocol with cryomilling against the conventional 15 g AOAC QuEChERS method. Key goals include demonstrating comparable limits of quantitation, recovery, and reproducibility across incurred fruit and vegetable samples and quantifying cost and resource savings.

Methodology and Instrumentation

Sample Preparation

• Use 2 g of homogenized or cryomilled matrix instead of 15 g.
• Extract with 2 mL acetonitrile containing 1 % acetic acid.
• Partition with AOAC QuEChERS salts, vortex, centrifuge, then perform dispersive SPE using PSA or a universal sorbent blend.
• Spike QC and calibration samples to establish recovery and linearity down to 0.5 ng/g.

Instrumentation

• Agilent 7890 GC coupled to a 7010 Triple Quadrupole MS with a High Efficiency Source.
• Multi-Mode Inlet with back-flush capability for reduced matrix load.
• Data acquisition and processing managed by MassHunter software.

Main Results and Discussion

Limits of quantitation of 5 ng/g or lower were achieved for over 95 % of 126 targeted pesticides in carrot, tomato, and celery. In curred samples, 86–90 % of compounds reached 1 ng/g LOQ. Comparative analysis showed strong agreement between 15 g and 2 g protocols, both homogenized and cryomilled. Representative analytes such as pyriproxyfen, iprodione, and fenbuconazole exhibited virtually identical concentrations across approaches. Figures and tables indicated that cryomilling provided a more uniform particle size but was not strictly required for equivalent analytical performance.

Benefits and Practical Applications

Mini-QuEChERS with a smaller sample size offers multiple advantages:

• Over 40 % reduction in sample preparation costs due to decreased solvent, sorbent, and labeled standard consumption.
• Lower solvent waste and reduced environmental impact.
• Compatibility with existing laboratory equipment and workflows without extensive reoptimization.
• Improved sample throughput and reduced storage requirements for matrices and extracts.
• Enhanced instrument uptime through lower matrix injection and extended maintenance intervals.

Future Trends and Applications

Emerging developments may include integration of automated cryogenic milling units into high-throughput platforms, expansion of mini-QuEChERS to other complex matrices such as grains and processed foods, and adaptation to liquid chromatography-mass spectrometry workflows. Advances in ion source design and ultra-sensitive detectors will further drive sample size reduction and lower detection limits.

Conclusion

The mini-QuEChERS protocol employing 2 g samples and optional cryomilling delivers equivalent analytical performance to the standard 15 g AOAC method across a broad pesticide panel. Substantial cost and solvent savings, along with seamless method transfer to advanced GC/MS/MS systems, make this approach attractive for routine monitoring and regulatory compliance testing in food safety laboratories.

Reference

Stevens J and Churley M. Representative Two-gram Incurred Food Samples Using Mini-QuEChERS, Cryomilling and GC/MS/MS Analysis with a High Efficiency Ion Source. Agilent Technologies Application Note WP214, ASMS 2016.