Improved GCxGC-TOFMS Workflow to More Efficiently Meet Compliance and Confidence Requirements for Fragrance Allergen Analysis Using the LECO Pegasus BTX 4D

Improved GCxGC-TOFMS Workflow for Fragrance Allergen Analysis — LECO Pegasus BTX 4D (Application Note Summary)

Importance of the topic
Regulatory frameworks, notably the EU Regulation (EU) 2023/1545 updating Annex III to Regulation (EC) 1223/2009, significantly expand the list of fragrance allergens that must be declared on cosmetic product labels. Compliance requires reliable quantification of many structurally diverse compounds at low concentration thresholds (0.001% for leave-on, 0.01% for rinse-off products). Traditional GC-MS workflows recommended by IFRA typically require multiple injections on columns of different polarity and different acquisition conditions, increasing instrument time, sample handling, and potential for data integration errors. A single-run, high-resolution approach that delivers robust targeted quantitation while preserving full-scan capability for non-target and retrospective analysis is therefore highly valuable for industry laboratories, QA/QC, and regulatory testing.
Objectives and overview of the study
The application note describes development and demonstration of a GC×GC coupled to time-of-flight mass spectrometry (GCxGC-TOFMS) workflow using the LECO Pegasus BTX 4D platform with a QuadJet thermal modulator. The goals were to:

• Resolve and quantify a comprehensive panel of 57 fragrance allergens (plus isomers) in a single analytical run;
• Deliver calibration linearity, precision, and accuracy compatible with regulatory needs;
• Reduce overall sample throughput burden versus multiple 1D GC runs;
• Show compatibility with complex matrices (fine fragrances) and non-target screening/retrospective data mining.

Methods and analytical procedure
The study used two commercially available allergen mixes to prepare calibration standards and replicate test solutions following IFRA guidance. Key experimental elements include:

• Standards and internal standards: two Millipore Sigma mixes (A1, A2) prepared at 0.2–25 µg/mL in MTBE; internal standards 1,4-dibromobenzene and 4,4'-dibromobiphenyl added at 10 µg/mL.
• Injection and chromatography: 1 µL injection with 1:100 split; primary column VF-35ms (60 m × 0.25 mm × 0.25 µm) coupled to a short polar MEGA-WAX-HT second-dimension column (0.6 m × 0.15 mm × 0.15 µm) via QuadJet LN2-cooled thermal modulation.
• Oven and modulation: GC oven program starting at 65 °C with multi-step ramps to 270 °C; secondary oven and modulator at +15 °C offsets; variable modulation period 1.4–2.8 s.
• Mass spectrometry and data acquisition: LECO Pegasus BTX 4D TOFMS, ion source 250 °C, mass range 35–400 m/z, acquisition at 150 spectra/s; ChromaTOF used for processing with quantifier/qualifier masses and 15% ion-ratio tolerance.
• Performance testing: calibration across eight levels (0.2–25 µg/mL); precision/accuracy assessed with eight randomized replicate injections at 1 and 10 µg/mL.

Main results and discussion
- Chromatographic separation: GCxGC contour plots show baseline-resolved separation for the full target list in a single run, effectively resolving first-dimension coelutions and providing clean mass spectra for targets and nearby interferences.
- Linearity and sensitivity: Calibration curves across 0.2–25 µg/mL produced excellent linearity, with an average correlation coefficient R2 ≈ 0.9988 for the allergen panel, supporting reliable quantitation across the tested range.
- Precision and accuracy: Replicate injections (n=8) at 1 and 10 µg/mL for representative compounds (alpha-pinene, geraniol, lilial, coumarin, eugenyl acetate, benzyl cinnamate) yielded relative standard deviations below 5% and mean repeatability within acceptable limits, indicating robust intra-run precision and accurate recovery under the described conditions.
- Matrix performance and non-target findings: Analysis of a commercial fine fragrance demonstrated the method’s ability to resolve complex regions where 1D GC would show overlap; targeted allergen isoeugenyl acetate was cleanly quantified and a contaminant (diethyl phthalate) was identified simultaneously. Full-scan TOFMS enables extension to additional analytes (e.g., phthalates) and retrospective interrogation of archived data.
- Operational advantages: Single-run acquisition reduces the number of injections and manual data merging required by multi-column 1D approaches, supports higher dilution factors (reducing injector/liner contamination), and shortens instrument maintenance intervals.
Benefits and practical applications

• Regulatory compliance: Efficiently supports quantitative workflows required by EU and other region-specific allergen labeling rules.
• Throughput and cost efficiency: Reduces analysis time per sample by consolidating multiple targeted methods into one GCxGC-TOFMS run.
• Analytical confidence: Superior separation and high-fidelity full-scan spectra improve identification certainty and quantitation in complex matrices.
• Flexibility: Single-run ability to add or retrospectively monitor additional targets without re-running samples.

Used instrumentation

• GC×GC platform: LECO GCxGC with QuadJet thermal modulator (liquid nitrogen cooled).
• GC columns: VF-35ms (60 m × 0.25 mm × 0.25 µm) first dimension; MEGA-WAX-HT (0.6 m × 0.15 mm × 0.15 µm) second dimension.
• Injector: 1 µL split (1:100), inlet 280 °C, Topaz Low Pressure Drop Precision liner.
• Carrier gas: Helium, 1.30 mL/min ramped to 1.6 mL/min.
• TOFMS: LECO Pegasus BTX 4D, ion source 250 °C, transfer line 270 °C, mass range 35–400 m/z, 150 spectra/s acquisition.
• Software: ChromaTOF for deconvolution, quantitation, and library matching.

Summary of figures and tables (key points)

• Contour plots (Figures): Demonstrate clear 2D separation of the complete allergen list and of a complex fragrance sample where GCxGC resolves first-dimension coelutions.
• Calibration plots and spectra (Figure examples): Representative calibration curves and library matches confirm linearity and spectral fidelity for selected allergens.
• Precision/accuracy plots: Replicate injection data show RSDs below 5% at two concentration levels, supporting method precision and repeatability.
• Appendix table: Provides quantifier/qualifier masses and per-compound R2 values for the 57-target panel (most R2 values ≥0.997), supporting the reported quantitation performance.

Future trends and potential applications

• Broader validation: Extension of the workflow to additional matrices (skin products, ingredients, natural extracts) and inter-laboratory validation for regulatory adoption.
• Automation and data pipelines: Integration with automated sample preparation and targeted reporting templates to further reduce analyst time.
• Advances in modulation: Development of cryogen-free modulators or alternative thermal modulation approaches to simplify operation and reduce LN2 dependence.
• Higher-resolution/AI-driven processing: Coupling high-speed acquisition with advanced deconvolution, chemometrics, and library-search algorithms to expand non-target discovery and reduce manual review.
• Regulatory harmonization: Alignment of multi-region target lists using retrospective TOFMS datasets to simplify compliance across export markets.

Conclusion
The demonstrated GCxGC-TOFMS workflow on the LECO Pegasus BTX 4D provides a compelling single-run strategy for comprehensive fragrance allergen analysis. It achieves high chromatographic resolution, robust quantitation across a wide dynamic range, and preserves full-scan capabilities for non-target screening and retrospective analysis. The method reduces total instrument runs and manual data reconciliation relative to conventional multi-run GC-MS approaches, offering practical benefits for laboratories tasked with routine allergen compliance and complex matrix characterization.
Reference

1. Regulation (EC) No 1223/2009 of the European Parliament and of the Council on cosmetic products (consolidated texts and updates reflected in Regulation (EU) 2023/1545).
2. Dutriez T., et al. Method of resolving allergens in perfume ingredients. WO2017207467A1, 2016.
3. International Fragrance Association, Analytical Working Group. Analytical Method to Quantify 57 Suspected Allergens (and isomers) in Ready to Inject Fragrance Materials by Gas Chromatography and Mass Spectrometry. 2016.