Automated sample preparation using CTC PAL3 to analyze >570 pesticides in an orange by the combination of GC/MS/MS and LC/MS/MS techniques

Importance of the Topic

Automated sample preparation integrated with GC/MS/MS and LC/MS/MS enables high-throughput, reliable screening of hundreds of pesticide residues in food matrices. This approach addresses the limitations of manual QuEChERS workflows, which are labor-intensive, time-consuming, and prone to human error, challenges that were amplified during periods of restricted laboratory access such as the COVID-19 pandemic.

Objectives and Study Overview

The study aimed to develop and validate a fully automated QuEChERS-based workflow on the CTC PAL3 autosampler for the extraction and cleanup of over 570 pesticide analytes in orange samples. Key goals included comparing method performance against traditional manual preparation across three spiking levels (10, 20, 50 µg/kg) and evaluating linearity, accuracy, and precision for both GC/MS/MS and LC/MS/MS platforms.

Methodology and Instrumentation

Sample preparation steps were scripted on the CTC PAL3 system to perform: weighing of homogenized orange (5 g), acetonitrile extraction (10 mL), vortex mixing, centrifugation, QuEChERS EN salt addition, µSPE cleanup (45 mg cartridges), elution with acidified ACN, and internal standard addition. Overlapping scripts minimized idle time between batches.
Used Instrumentation:

• CTC PAL3 autosampler for fully automated QuEChERS workflow
• Agilent 1290 Infinity II HPLC coupled to 6470 triple quadrupole MS for LC/MS/MS
• Agilent GC system with triple quadrupole MS for GC/MS/MS
• µSPE multiwell plates and cartridges for sample cleanup

Main Results and Discussion

The automated workflow delivered superior linearity, with over 90% of analytes showing R2 ≥ 0.995 in both LC and GC methods, compared to 84–92% for manual prep. Recovery distributions centered within the 70–120% range for the majority of compounds and spike levels, with the automated method exhibiting fewer low- or high-bias outliers. Precision studies yielded RSDs below 20% for more than 85% of analytes, demonstrating robust repeatability that matched or exceeded manual performance.

Benefits and Practical Applications

• Significant reduction in hands-on labor and operator dependency
• Enhanced throughput for multi-residue pesticide screening
• Improved consistency and reduced human error
• Adaptable to other food matrices and regulatory testing

Future Trends and Potential Applications

Future developments may integrate AI-driven optimization for extraction and cleanup, expanding the method to emerging contaminants and complex matrices. Cloud-based data processing and remote system monitoring will further streamline regulatory compliance and real-time quality assurance.

Conclusion

The fully automated QuEChERS workflow on the CTC PAL3 autosampler, coupled with GC/MS/MS and LC/MS/MS detection, offers a high-efficiency, low-cost solution for comprehensive pesticide residue analysis in oranges, outperforming manual methods in linearity, accuracy, and precision.

References

• GB2763-2021: National food safety standard - Maximum residue limits for pesticides in food
• GB23200.121-2021: Determination of 331 pesticides and metabolites in foods of plant origin by LC/MS/MS
• GB23200.121-2018: Determination of 208 pesticides and metabolites in foods of plant origin by GC/MS/MS