Assessing Washing Methods for Reduction of Pesticide Residues in Tomatoes and Other Produce Using LC/MS and GC/MS

Significance of the Topic

Global trade expansion has increased the potential for pesticide residues on imported fruits and vegetables, which pose health risks including neurological and endocrine disruption. Effective decontamination methods are essential to minimize consumer exposure and ensure food safety.

Objectives and Study Overview

This application note evaluates various washing procedures, with and without ultrasound, for removing a panel of nine common pesticides from tomatoes. Bench-scale experiments simulated pesticide application, followed by laboratory washing treatments. A commercial-scale flume was also tested to assess real-world efficacy on multiple produce items.

Methodology

1. Contamination model: Tomatoes were dipped in standard pesticide mixtures for 5 or 30 seconds to achieve uniform surface loading.
2. Washing treatments: Water at 5, 10, and 22 °C; sodium hypochlorite (80 mg/L); peroxyacetic acid (80 mg/L); Tween 20 (0.1%), each with or without 5-minute sonication.
3. Sample preparation: QuEChERS extraction per AOAC 2007.1.
4. Analysis: LC/MS/MS (Agilent 1260/6460) for nonvolatile pesticides and GC/MS (Agilent 7890A/5975C) for volatile analytes; quantification by selective ion monitoring; statistics via ANOVA (P<0.05).

Instrumentation

• LC/MS/MS: Agilent 1260 Infinity LC with 6460 Triple Quadrupole and JetStream.
• GC/MS: Agilent 7890A GC with 5975C MSD and HP-5MS UI column.

Main Results and Discussion

Pesticide Contamination Model

Both 5- and 30-second dipping protocols yielded consistent pesticide loading on tomatoes; the 5-second dip was selected to mimic spray exposure.

Effect of Washing Temperature

Ambient water (22 °C) produced significantly higher residue removal (40–90%) for most pesticides compared to 5 or 10 °C washes, reflecting enhanced pesticide diffusion at warmer temperatures.

Effect of Washing Protocols

Sonication significantly improved removal only when combined with plain water, notably for permethrin. Chemical agents (sodium hypochlorite, peroxyacetic acid, Tween 20) achieved similar reductions with or without ultrasound, indicating limited added benefit from sonication in those cases.

Commercial-Scale Washing Effectiveness

A pilot plant flume wash (1 minute, room temperature) reduced pesticide residues on tomatoes, apples, peppers, peaches, oranges, and lemons by 40–90%, demonstrating scalable efficacy.

Benefits and Practical Applications

The study provides data-driven guidance for optimizing household and industrial washing processes, including selection of temperature, duration, and treatment agents to maximize residue removal.

Future Trends and Potential Applications

Further research may explore eco-friendly detergents, advanced ultrasound technologies, integration with real-time monitoring, and application to diverse produce and pesticide classes.

Conclusion

Validated washing protocols, particularly ambient water rinses with optional sonication, can substantially reduce pesticide residues on produce. Adoption of such procedures supports improved food safety and regulatory compliance.

References

1. F. Gale and J. C. Buzby. Imports from China and food safety issues. USDA Economic Research Service, Economic Information Bulletin 52 (2009).
2. F. Al-Taher, Y. Chen, P. Wylie, J. Cappozzo. Reduction of pesticide residues in tomatoes and other produce. Journal of Food Protection 76, 510–515 (2013).