Analysis of PAHs in Infant Formula and Blueberries Using QuEChERS and GCxGC-TOFMS

Significance of the Topic

Polycyclic aromatic hydrocarbons (PAHs) represent a major health concern due to their carcinogenic potential and widespread occurrence in foodstuffs. Up to 70 % of non‐occupational PAH exposure in non‐smokers is linked to diet. Reliable, rapid detection of trace PAHs in complex matrices such as infant formula and fruit is therefore critical for consumer safety and regulatory compliance.

Study Objectives and Overview

This work evaluates a combined approach using QuEChERS sample preparation and two‐dimensional gas chromatography time‐of‐flight mass spectrometry (GCxGC-TOFMS) to detect and identify 20 target PAHs in liquid infant formula and blended blueberries. The goal is to assess method speed, sensitivity, and ability to resolve closely eluting isomer pairs.

Methodology

• Sample Preparation: Ten grams of spiked matrix was extracted with acetonitrile and Qsep salts following the QuEChERS protocol. After centrifugation and optional dSPE cleanup, the extract was acidified and transferred to the autosampler.
• Analytes: Internal standard phenanthrene-d10 and an EPA PAH mixture were spiked to achieve on‐column masses from 10 pg to 5 ng per compound.

Instrumentation

• GCxGC-TOFMS Platform: LECO Pegasus 4D with a splitless inlet and helium carrier gas at 1.40 mL/min.
• Column Set: 30 m × 0.25 mm × 0.25 µm Rxi-1ms primary column and 1.0 m × 0.10 mm × 0.10 µm RTX-17 secondary column. Oven program: 50 °C hold for 30 s, ramp at 10 °C/min to 300 °C, then 10 min hold. Secondary oven offset by +10 °C. Modulation period of 5 s with 0.80 s hot pulse.
• MS Conditions: Electron ionization at 70 eV, source temperature 200 °C, detector voltage 1600 V, mass range 50–500 m/z, acquisition rate 100 spectra/s.

Main Results and Discussion

All 20 PAH targets were separated and detected at sub‐nanogram levels. Critical isomer pairs such as phenanthrene/anthracene, benzo(b)/(k)fluoranthene, and indeno(1,2,3‐cd)pyrene/dibenzo(a,h)anthracene were baseline resolved under the chosen conditions. Early‐eluting compounds achieved detection limits below 1 pg on-column due to reduced band broadening. GCxGC contour plots demonstrated clear differentiation of PAHs from matrix interferences in both infant formula and blueberry extracts. Calibration curves for pyrene exhibited excellent linearity (R2 ≥ 0.997) over both picogram and nanogram ranges.

Benefits and Practical Applications

This workflow delivers rapid, comprehensive PAH screening in complex food matrices within approximately one hour total analysis time. The high sensitivity and separation power of GCxGC-TOFMS coupled with a simple QuEChERS extraction make it well suited for quality assurance, regulatory monitoring, and swift response in potential food contamination events.

Future Trends and Applications

Advances may include shorter modulation periods for simpler matrices, integration of automated sample preparation, expansion to other contaminants, and miniaturized GCxGC systems for field deployable analyses. Enhanced data processing algorithms will further streamline identification and quantification of trace organic pollutants.

Conclusion

The combined QuEChERS and GCxGC-TOFMS approach provides a fast, reliable, and sensitive method for the determination of PAHs in challenging food matrices. Its robust performance in separating isomeric compounds and low detection limits highlights its value for routine food safety testing.

References

1. Skupinska K.; Misiewicz I.; Kasprzycka-Guttman T. Acta Pol Pharm 61(3):233–240 (2004).
2. Restek Application Note 805-01-002.