Comparison of Screening Method (Py-GC/MS) and Quantitative Method (Solvent Extraction–GC/MS) for Phthalate Esters Analysis

Importance of the Topic

Phthalate esters are widely used as plasticizers in PVC materials but pose reproductive toxicity risks. From 2019, four phthalates (DIBP, DBP, BBP, DEHP) became restricted under the amended RoHS Directive for electrical and electronic equipment. Accurate and efficient screening is critical for regulatory compliance and environmental safety.

Study Objectives and Overview

This study compares a pyrolysis–GC/MS screening system (Py-Screener) with a conventional solvent extraction–GC/MS quantitative method. The goal was to evaluate whether the rapid, solvent-free Py-GC/MS approach yields equivalent quantitative results at the regulatory threshold of 1000 mg/kg.

Methodology and Instrumentation

Certified reference material (KRISS CRM 113-03-006) and two black rubber samples (A and B) were analyzed.

Used Instrumentation

• Pyrolysis System: EGA/PY-3030D multi-shot pyrolyzer
• GC-MS Platform: Shimadzu GCMS-QP2010 Ultra
• Columns: Ultra ALLOY-PBDE (15 m×0.25 mm ID, 0.05 µm) for Py-GC/MS; HP-5MS (30 m×0.25 mm ID, 0.25 µm) for solvent extraction
• Sample Preparation (Solvent Extraction): THF dissolution, acetonitrile precipitation, anthracene-d10 internal standard
• Calibration: Single-point at 1000 mg/kg for Py-GC/MS; five-point (0.5–10 µg/mL) with internal standard for conventional GC/MS

Main Results and Discussion

• Certified Reference Material: Recoveries ranged from 92.9 % to 109.0 %, confirming accuracy of the Py-Screener method.
• Sample A (DEHP): Py-GC/MS reported 3923 mg/kg vs 3162 mg/kg (solvent extraction), a 124 % relative ratio. Repeatability (%RSD) was 5.1 % (Py-GC/MS) and 6.2 % (solvent extraction).
• Sample B (DBP, BBP, DEHP, DINP, DIDP): Quantitative ratios to solvent extraction were 108 % (DBP), 71 % (BBP), 68 % (DEHP), 104 % (DINP) and 100 % (DIDP). Py-GC/MS precision (%RSD) was 3.3–5.5 %, compared to 4.2–16.6 % for solvent extraction.
• Screening Performance: Single-point calibration at the 1000 mg/kg action level provides clear pass/fail decisions. High boiling phthalates near the calibration point showed good agreement; low-boiling compounds exhibited larger deviations.
• Limitations: Single-point calibration is not suitable for measurements far outside the regulatory threshold or for full quantitative profiling. In such cases, follow-up analysis with solvent extraction GC/MS is recommended.

Benefits and Practical Applications

The Py-Screener offers rapid, solvent-free sample preparation and automated data processing. It reduces analysis time and solvent waste, making it ideal for high-throughput screening of phthalates in compliance testing under RoHS requirements.

Future Trends and Opportunities

• Development of multi-point calibration protocols to extend quantitative range.
• Application to additional regulated plasticizers and emerging contaminants.
• Integration with automated sampling and data management for higher throughput.
• Combination with complementary techniques (e.g., LC-MS) to analyze nonvolatile additives.

Conclusion

The Py-Screener Py-GC/MS method provides equivalent screening accuracy to traditional solvent extraction–GC/MS at the 1000 mg/kg regulatory level. Its minimal sample preparation, reduced solvent use, and fast turnaround make it a valuable tool for routine phthalate compliance testing. For comprehensive quantitation across wider concentration ranges, a combined workflow with solvent extraction GC/MS is advised.

References

1. Commission Delegated Directive (EU) 2015/863 of 31 March 2015 amending Annex II to Directive 2011/65/EU.
2. Ministry of Health and Welfare Notification No. 370: Specifications and Standards for Food and Food Additives.
3. EN 14372:2004, Child Use and Care Articles – Cutlery and Feeding Utensils.
4. ASTM D3421-75, Recommended Practice for Extraction and Determination of Plasticizers from PVC.
5. CPSC-CH-C1001-09.3, SOP for Determination of Phthalates.
6. ISO 8124-6:2014, Safety of Toys – Certain Phthalate Esters.
7. ISO 14389:2014, Textiles – Determination of Phthalate Content (THF Method).
8. ASTM D7823-14, Test Method for Low-Level Regulated Phthalates in PVC by Thermal Desorption–GC/MS.
9. Maruyama F. et al., Anal. Sci., 2015, 31(3).