Automated QuEChERS Extraction for the Determination of Pesticide Residues in Foods using Gas Chromatography/ Mass Spectrometry

Importance of the topic

Monitoring pesticide residues in food is critical for public health and regulatory compliance. QuEChERS sample preparation methods offer quick and effective extraction but still require multiple manual steps, leading to variability and limited throughput. Automating dispersive solid-phase extraction (dSPE) addresses these challenges by reducing labor, improving consistency, and enhancing laboratory productivity.

Objectives and Study Overview

This study aims to develop and validate a fully automated workflow for QuEChERS extract cleanup and GC-MS analysis of pesticide residues in diverse food matrices. By integrating micro-scale dSPE kits with a robotic autosampler and thermal desorption injection, the method seeks to streamline sample preparation and detection.

Methodology and Instrumentation

Automated cleanup was performed on 1 mL QuEChERS extracts using Agilent SampliQ QuEChERS dSPE kits for fatty samples. A GERSTEL MultiPurpose Sampler (MPS) equipped with an Anatune CF-100 centrifuge carried out mixing, centrifugation, and sorbent contact. Cleaned extracts were injected using a GERSTEL Thermal Desorption Unit (TDU) with Automated Liner Exchange (ATEX) into an Agilent 7890 GC coupled to a 5975C Inert XL MSD. Key parameters:

• TDU solvent vent: 3 min at 100 °C, 50 mL/min
• TDU desorption: 280 °C, 720 °C/min ramp
• PTV inlet: splitless for 1.2 min, ramp from 25 °C to 280 °C
• GC column: 30 m Rxi-5Sil MS, 0.25 mm ID, 0.25 µm film
• Oven program: 60 °C (1 min), 10 °C/min to 310 °C (5 min)
• Carrier gas: He at 1 mL/min

Main Results and Discussion

Visual comparison of spinach and ginseng extracts before and after dSPE cleanup showed effective removal of chlorophyll and fatty residues. Thermal desorption injection prevented non-volatile residues from entering the inlet, reducing maintenance. Chromatograms of oranges, spinach, hazelnuts, and ginseng spiked at 50 ppb illustrated clear detection of 15 pesticides. Recovery values ranged from 38 % to 185 %, with most analytes falling within acceptable limits. Triplicate injections of ginseng extract yielded relative standard deviations between 2 % and 16 %, demonstrating good precision.

Benefits and Practical Applications

This automated workflow minimizes manual solvent handling, lowers inlet maintenance, and standardizes sample processing to boost throughput. Matrix elimination via ATEX thermal desorption enhances detection sensitivity and extends maintenance intervals, making the approach well suited for routine pesticide monitoring in food safety and QA/QC laboratories.

Future trends and applications

Advances in online sample preparation, high-resolution mass spectrometry, and non-targeted screening will expand the scope of automated residue analysis. Integration with data analytics and robotic sample handling promises further gains in throughput and trace-level detection, supporting large-scale food surveillance and compliance initiatives.

Conclusion

The integration of automated dSPE QuEChERS cleanup with ATEX thermal desorption and GC-MS enables a streamlined, high-precision workflow for pesticide residue analysis. This approach improves laboratory efficiency, consistency, and analytical performance while reducing manual steps and instrument downtime.

References

Wong J. (FDA) for providing QuEChERS extracts used in this study.