Trace Level Organochlorine and Organophosphorous Pesticides Analysis in Green Tea by SBSE-GC-TOFMS

Trace Level Organochlorine and Organophosphorous Pesticides Analysis in Green Tea by SBSE-GC-TOFMS

Significance of the Topic

Monitoring organochlorine and organophosphorous pesticides in green tea is essential for food safety and regulatory compliance. Strict limits set by the European Union, Japan, and the US EPA drive the need for highly sensitive analytical methods. Given the global consumption of green tea and its health reputation, trace-level detection of pesticide residues supports public health protection and quality assurance.

Objectives and Study Overview

This study aimed to develop and validate a rapid, sensitive workflow for quantifying 22 OCP/OPP pesticides in brewed green tea. Key goals included achieving detection limits at or below 10 parts-per-trillion (ppt), building reliable calibration curves from 10 to 500 ppt, and testing multiple tea brands to assess background contamination.

Methodology and Instrumentation

The analysis combined stir bar sorptive extraction (SBSE) with thermal desorption and gas chromatography time-of-flight mass spectrometry (GC-TOFMS). Main steps:

• Sample Preparation: Brewing green tea, spiking with pesticide standards (10–500 ppt).
• Extraction: 10 mL aliquots stirred with PDMS Twister bar at 1 000 rpm for 60 min.
• Thermal Desorption: Automated tube introduction, desorption at elevated temperature into a cryogenically cooled inlet.
• Chromatography: 10 m × 0.18 mm Rtx-5 LTM column, He carrier, 40 °C to 300 °C ramp.
• Detection: Pegasus GC-TOFMS, 50–510 amu range, 20 spectra/s acquisition, deconvolution algorithms for peak identification.

Main Results and Discussion

Calibration curves were linear (r > 0.990) for 21 of 22 pesticides over 10–500 ppt; Disulfoton showed r = 0.9876 from 50–500 ppt. Limits of detection were ≤ 10 ppt for all but one target. Deconvolution enabled clear identification of deeply coeluting analytes, illustrated by heptachlor epoxide buried under matrix peaks. No significant pesticide residues were found in most tea samples, though trace levels at ppt–ppb were detected in three brands.

Benefits and Practical Applications

The SBSE-GC-TOFMS approach offers:

• Minimal sample preparation and solvent consumption.
• High sensitivity for trace pesticide quantitation in complex matrices.
• Rapid throughput with a total run time of ~8.2 min per sample.
• Automated deconvolution for reliable compound identification.

Future Trends and Potential Applications

Emerging SBSE sorbents and advanced TOFMS platforms may further lower detection limits and expand analyte scope. Integration with high-resolution MS and real-time data processing could enable in-line quality control in beverage production. Broader application to other food matrices and environmental samples is anticipated.

Conclusion

The described SBSE-GC-TOFMS method delivers fast, accurate, and highly sensitive quantitation of organochlorine and organophosphorous pesticides in green tea. Its robustness and low detection limits support regulatory testing and quality assurance in tea products.