Determination of Dioxin in Food by GC-MS/MS Coupled with Boosted Efficiency Ion Source (BEIS)

Importance of Topic

The determination of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in food matrices is critical due to their persistence, bioaccumulation and potential health risks. Regulatory agencies require high-sensitivity and high-selectivity analytical methods to monitor trace-level contaminants and ensure food safety.

Objectives and Study Overview

This study evaluates a gas chromatography–tandem mass spectrometry (GC-MS/MS) method using the Shimadzu GCMS-TQ8050 NX instrument equipped with a boosted efficiency ion source (BEIS). The goals were to develop an optimized multiple reaction monitoring (MRM) method for PCDD/F analysis in food, assess linearity, accuracy and precision using low-level standards, and validate real-sample performance against consensus toxicity equivalent (TEQ) values from the Norwegian Institute of Public Health (NIPH).

Methodology and Instrumentation

Sample Preparation:

• Standards: Native PCDD/Fs and 13C-labeled internal standards from Wellington Laboratories.
• Calibration: Seven-point curves from 0.01 to 10 ng/mL (CSLQ to CS3).
• Food samples: Extracted following EPA-1613B, lipid content determined gravimetrically, cleaned on multilayer silica gel, alumina and carbon columns.

Instrumental Conditions:

• GC Column: DB-5 MS (60 m × 0.25 mm × 0.25 µm).
• Oven Program: 120 °C (1 min) ramp to 220 °C at 43 °C/min (15 min), then to 250 °C and 260 °C, final hold at 310 °C.
• Carrier Flow: Constant at 1.5 mL/min, injection volume 2 µL, EI 70 eV.
• BEIS Conditions: Source 230 °C, interface 300 °C, CID pressure 150 kPa, detector voltage 1.8 kV.
• Acquisition: MRM with loop time 1.4 s; transitions defined for each congener and its labeled analogue.

Main Results and Discussion

Calibration and Linearity:

• All congeners displayed linear response (R² > 0.99) over the calibration range.
• Average relative response factors (RRFs) ranged from 0.91 to 1.39, with RSDs < 12%.

Accuracy and Precision:

• Quantification at the lowest standard (CSLQ×2) yielded relative errors below 20% for all components.
• Method repeatability met regulatory precision criteria at trace levels.

Real Sample Analysis:
The TEQ values obtained from various food types matched NIPH consensus data, demonstrating the method’s robustness and suitability for routine monitoring.

Benefits and Practical Applications

The developed GC-MS/MS method with BEIS offers:

• Enhanced sensitivity for trace-level PCDD/F detection.
• Improved ionization efficiency and signal stability.
• Faster analysis times compared to high-resolution MS alternatives.
• Applicability to QA/QC laboratories and regulatory compliance testing.

Future Trends and Potential Applications

Emerging developments may include:

• Integration with automated sample preparation for higher throughput.
• Coupling with high-resolution mass analyzers for broader screening of dioxin-like compounds.
• Miniaturized or portable GC-MS systems for on-site food safety monitoring.

Conclusion

The Shimadzu GCMS-TQ8050 NX with BEIS and MRM acquisition provides a reliable, accurate and sensitive approach for quantifying PCDD/Fs in food. The method meets regulatory requirements for linearity, precision and accuracy, and its performance aligns with established consensus TEQ values.