Stir Bar Sorptive Extraction (TwisterTM) RTL-CGC-MS. A Versatile Method to Monitor more than 400 Pesticides in Different Matrices (Water, Beverages, Fruits, Vegetables, Baby Food)

Significance of the Topic

Monitoring pesticide residues across diverse food and environmental samples is critical for consumer safety, regulatory compliance and environmental protection. Solid matrices such as fruits, vegetables and baby food present particular analytical challenges due to complex composition and low analyte concentrations. A universal, high‐throughput approach capable of detecting hundreds of pesticides in liquids and solids can streamline laboratory workflows and improve confidence in multi‐residue screening.

Objectives and Study Overview

This study aimed to develop and validate a versatile stir bar sorptive extraction (SBSE) method combined with thermal desorption and retention time locked capillary GC-MS (SBSE-TDU-RTL-GC-MS) for simultaneous monitoring of over 400 pesticides in water, beverages, fruits, vegetables and baby food. Automated sample handling and data processing were integrated to maximize throughput and ensure consistent identification and quantitation.

Methodology and Sample Preparation

• Solid samples (15 g) were homogenized with 30 mL methanol using Ultraturrax and ultrasound.
• A 1 mL aliquot of extract was diluted with 10 mL water for SBSE.
• PDMS‐coated stir bars (Twister, 10 mm × 0.5 mm df or 20 mm × 1.0 mm df) performed 60 min extraction at ambient conditions.
• Thermal desorption in Gerstel TDU transferred analytes directly to a retention time locked GC-MS system.

Instrumentation Used

• Gerstel Thermal Desorption Unit (TDU) with MPS-2 robotic autosampler (40→280 °C ramp)
• Gerstel cooled injection system (CIS-4 PTV, –150→280 °C)
• Agilent 6890 GC with 30 m × 250 µm, 0.25 µm HP5-MS capillary column
• Helium carrier gas, constant pressure
• Agilent 5973N single quadrupole mass spectrometer, full scan m/z 40–500
• Agilent RTLpest retention time locked pesticide library and Result Screener software

Main Results and Discussion

• A total of 440 GC‐amenable pesticides were screened; 367 compounds showed SBSE recoveries ≥ 75% on 10 mm Twisters (24 µL PDMS) and ≥ 93% on 20 mm devices (116 µL PDMS).
• Recoveries were grouped into four ranges (10–24%, 25–49%, 50–74%, 75–100%) to predict suitability based on log Kow.
• Thermally sensitive pesticides marked with an asterisk were recovered > 70%, demonstrating mild desorption conditions.
• Automated identification of permethrin II, benalaxyl, vinclozolin, tolylfluanid and procymidone in grapes and apples illustrated selective extracted ion chromatograms and mass spectra matching the RTL library.
• Quantitation options included external calibration (negligible matrix effects for fruits and vegetables), standard addition and isotope dilution. Limits of quantitation required for stringent matrices such as baby food were readily achieved.

Benefits and Practical Applications

• High throughput: 98 samples per run using robotic automation.
• Wide coverage: over 400 pesticides in water, beverages and solid foods.
• High sensitivity and selectivity: sub-µg/L detection in aqueous samples.
• Minimal matrix effects for common food matrices.
• Flexible quantitation: external, standard addition or isotope dilution.
• Automated processing reduces labor and subjectivity.

Future Trends and Opportunities

Enhancing SBSE-GC-MS methods may involve coupling to tandem MS for improved selectivity, expanding to polar and emerging contaminants with novel coatings, integrating machine learning for spectral deconvolution, miniaturizing extraction for in‐field screening and adopting green solvents and techniques for sustainable laboratories.

Conclusion

The SBSE-TDU-RTL-GC-MS approach offers a robust, automated multi-residue platform for routine monitoring of a broad range of pesticides in diverse matrices. High recoveries, sensitivity and throughput support compliance testing and research applications, while flexibility in quantitation strategies addresses challenging sample types such as baby food.

References

• Sandra P, Tienpont B, David F. A versatile method to monitor more than 400 pesticides in different matrices (water, beverages, fruits, vegetables, baby food) by SBSE-TDU-RTL-GC-MS. Application Note; 2003.
• Sandra P, Tienpont B, Vercammen J, Tredoux A, Sandra T, David F. Multi-residue analysis of pesticides in wine by SBSE-TDU-RTL-GC-MS. J Chromatogr A. 2001;928:117.