High-Resolution Accurate-Mass (HRAM) Phthalate Screening using Direct Analysis in Real Time (DART) Ambient Ionization

Importance of the Topic

Phthalic acid diesters (phthalates) are prevalent plasticizers in toys, flooring, personal care items, and food packaging. Classified as semi-volatile organic compounds with potential reproductive and carcinogenic effects, their regulatory limits demand reliable, rapid screening methods. Ambient ionization with high-resolution accurate mass (HRAM) detection offers a minimal-preparation approach that reduces cross-contamination and accelerates analysis.

Aims and Study Overview

This study demonstrates a direct analysis in real time (DART) ambient ionization source coupled to a Thermo Scientific Q Exactive Orbitrap mass spectrometer for rapid screening of phthalate esters. The workflow integrates full-scan HRAM detection with targeted single ion monitoring (SIM) and higher-energy collision-induced dissociation (HCD) MS2 to distinguish isomers and confirm positive findings.

Used Methodology and Instrumentation

• Sample Introduction: Stainless steel mesh screens loaded with standard or commercial material extracts; direct placement at fixed distance from the DART SVPA source.
• DART SVPA Ion Source: Operated at 200 °C with helium carrier gas to ionize analytes without solvent or glassware contact.
• Mass Spectrometer: Thermo Scientific Q Exactive orbitrap in positive ion mode. Full scan (m/z 100–1000, resolution 140 000, AGC target 1×10^6), SIM (isolation width 2 u, AGC target 1×10^5), MS2 (isolation width 2 u, AGC target 2×10^5, HCD with normalized collision energy 10).
• Acquisition Method: One 1.2 min method including 0.3 min blank for background monitoring, followed by sample introduction and sequential full scan, SIM, and MS2 events.

Main Results and Discussion

• Background Control: Ambient phthalate ions monitored prior to sample to prevent false positives due to laboratory contamination.
• Accurate-Mass Screening: Full-scan analysis provided <2 ppm mass accuracy for [M+H]+ ions of phthalate standards, enabling deconvolution of co-eluting species.
• MS2 Fingerprinting: HCD fragmentation produced characteristic product ions (e.g. m/z 149 as base peak for most diesters; absence of m/z 167 distinguishes DNOP). Fragment assignments confirmed with Mass Frontier software within 2 ppm deviation.
• Sample Survey: Thirty-six consumer items (lid gaskets, food packages, bags, shoes, wallets, sports gear) screened in under 2 min each. No regulated phthalates (DEHP, DBP, DiBP, BBP) detected; alternative plastic additives (ATBC, DEHA, AcPG, erucamide) were identified.

Benefits and Practical Applications

• Speed: Entire screening completed in approximately 1.2 minutes per sample without chromatography.
• Minimal Contamination: Direct sampling avoids solvents and glassware, reducing phthalate carry-over.
• High Confidence: HRAM full scan and MS2 fragmentation enable isomer discrimination and compound confirmation.
• Utility: Suitable for QA/QC laboratories, regulatory screening of food contact materials, and rapid on-site testing.

Future Trends and Potential Applications

• Quantitative Extension: Development of calibration protocols with defined reference materials for accurate quantitation.
• Method Integration: Coupling ambient ionization with microfluidic devices or in-line sampling for automated workflows.
• Expanded Libraries: Building spectral libraries of phthalates and related additives to support large-scale screening and data-mining by AI models.

Conclusion

The DART-Orbitrap HRAM approach provides a rapid, robust, and contamination-minimized workflow for comprehensive phthalate screening. Combining accurate-mass full scan, targeted SIM, and MS2 fingerprinting achieves confident compound identification in under two minutes per sample, supporting regulatory compliance and quality assurance in material analysis.

Reference

• The Federal Environment Agency, Germany.
• FDA Docket 02d-0325-c000018-02-vol1.pdf.
• Kamrin MA. Phthalate risks, phthalate regulation, and public health: a review. J Toxicol Environ Health B Crit Rev. 2009;12(2):157–74.
• Self RL et al. Rapid qualitative analysis of phthalates added to food and nutraceutical products by DART/Orbitrap mass spectrometry. Food Control. 2012;25:13–16.
• Rothenbacher T, Schwack W. Rapid and nondestructive analysis of phthalic acid esters in PVC toys by DART single-quadrupole mass spectrometry. Rapid Commun Mass Spectrom. 2009;23:2829–35.
• Kuki A et al. Fast identification of phthalic acid esters in PVC samples by DART tandem mass spectrometry. Int J Mass Spectrom. 2011;303:225–28.