Fast screening of pesticides in foods and agricultural products with probe electrospray ionization (PESI) tandem mass spectrometry

Importance of Topic

Pesticide residues in agricultural products present a significant challenge for food safety and regulatory compliance. Rapid and sensitive screening methods help ensure consumer protection and support quality control in production chains. Ambient ionization techniques such as probe electrospray ionization reduce sample preparation and increase analytical throughput.

Objectives and Study Overview

This study aims to develop a fast screening workflow for 80 commonly monitored pesticides in vegetables using probe electrospray ionization tandem mass spectrometry. The performance of PESI-MS/MS is assessed in terms of sensitivity, linearity, and applicability to real samples, with an emphasis on high throughput quantification.

Methodology and Instrumentation

Sample Preparation and Analysis Workflow

• Fresh cucumber samples were homogenized and extracted with water and acidified acetonitrile, followed by salt partitioning and centrifugation.
• Supernatant aliquots were dried and redissolved in water/isopropanol for direct PESI injection.

Used Instrumentation

• PESI source (Shimadzu DPiMS-8060)
• Triple quadrupole mass spectrometer (Shimadzu LCMS-8060)
• PESI parameters: ionization time 250 ms, discharge voltage +2.3 kV / -3.0 kV, cycle time 2.78 Hz
• MS parameters: desolvation line 200 C, heat block 30 C, MRM dwell time 0.075 ms per pesticide

Results and Discussion

• Ionization confirmation achieved for 74 of 80 target pesticides; six nonpolar or GC-amenable compounds remained undetected.
• Detection limits reached 1 ppb for typical analytes and over 90 percent of compounds were detectable below 10 ppb.
• Calibration linearity (R2 > 0.98) was established for 36 pesticides in matrix-matched curves over 5 to 100 ppb concentration range.
• Recovery studies in cucumber at 10 and 100 ug/kg spikes showed acceptable recovery (60-120 percent) for key analytes.

Benefits and Practical Applications

The PESI-MS/MS workflow enables pesticide screening in less than 1.5 minutes per sample. Minimal sample pretreatment and direct ionization greatly increase laboratory throughput, making this approach suitable for routine quality control in food safety laboratories.

Future Trends and Potential Applications

• Integration with high-resolution mass spectrometry for enhanced selectivity and unknown screening.
• Automation of sample handling to further reduce hands-on time.
• Extension to other food matrices and environmental samples.
• Application of machine learning for rapid data interpretation.

Conclusion

PESI tandem mass spectrometry on the DPiMS-8060 platform provides a fast and sensitive method for screening polar and semi-polar pesticides in agricultural products. Matrix calibration ensures reliable quantification and the workflow offers significant advantages in throughput and simplicity for food safety applications.

Reference

• K. Hiraoka et al. Rapid Communications in Mass Spectrometry, 2007, 21, 3139.
• K. Zaitsu et al. Analytical Chemistry, 2016, 88, 3556.
• K. Zaitsu et al. Analytical Chemistry, 2018, 90, 4695.