Analysis of Bisphenol A in PET Granules Using the Agilent 8890/5977C GC/MS System

Analysis of Bisphenol A in PET Granules by GC/MS — Summary

Significance of the topic

Polyethylene terephthalate (PET) is widely used in food and beverage packaging, and recycled PET (rPET) is increasingly permitted for food contact applications under new regulatory frameworks. Monitoring low‑level contaminants that can migrate from packaging into products — including bisphenol A (BPA) — is essential to ensure consumer safety and to validate recycling/decontamination processes. Reliable analytical methods for identification and quantification of BPA in PET support compliance, quality control, and risk assessment in industry and regulatory laboratories.

Objectives and study overview

This application note demonstrates a GC/MS workflow for detecting and quantifying BPA extracted from PET granules. Main aims were to establish sample preparation and derivatization procedures, define instrumental conditions on an Agilent 8890 GC coupled to a 5977C single‑quadrupole MS, generate a calibration range, determine method repeatability, and evaluate recovery from spiked PET samples.

Methodology

• Sample preparation: Approximately 200 mg of finely ground PET was extracted using 5 mL tetrahydrofuran (THF) with vortexing and sonication at 60 °C for 2 hours, followed by addition of 5 mL n‑hexane and vortexing. The combined extract was filtered through a 0.2 µm syringe filter. A 1 mL aliquot of the filtered extract was derivatized with 100 µL of N,O‑bis(trimethylsilyl)trifluoroacetamide (BSTFA) at 70 °C for 1 hour to form the trimethylsilyl (TMS) derivative of BPA prior to GC/MS analysis.
• Standard preparation: Serial dilutions produced calibration standards covering 10–500 ng/mL (final highest point 500 ng/mL). Standards were converted to TMS derivatives with BSTFA under the same conditions as samples.
• Derivatization: BSTFA was used to convert BPA to its TMS derivative, improving GC volatility and chromatographic behavior.

Used instrumentation

• Gas chromatograph: Agilent 8890 GC.
• Mass spectrometer: Agilent 5977C single‑quadrupole GC/MS.
• Column: HP‑5ms, 30 m × 0.25 mm, 0.25 µm film thickness (Agilent p/n 19091S‑433UI).
• GC conditions: inlet 250 °C; injection 1 µL, split 10:1; helium carrier gas, 1.2 mL/min constant flow; oven program 90 °C (2 min) → 15 °C/min → 300 °C (hold 12 min); transfer line 300 °C.
• MS conditions: inertplus/extractor ion source at 250 °C; quadrupole 150 °C; acquisition in SIM/scan with quantifier and qualifier ions (m/z 357, 372, 358, 73) and full scan 45–450 m/z.

Main results and discussion

• Retention time and identification: Derivatized BPA eluted at ~13.49 minutes. Library matching (NIST) provided a match score reported at 88.4, supporting compound identification.
• Calibration and sensitivity: A linear calibration range from 10 to 500 ng/mL was established. Method limit of quantification (LOQ) for the PET matrix was demonstrated at 500 ng/g (expressed per gram of PET), corresponding to the highest calibration point after appropriate sample handling and dilution.
• Precision: Six replicate injections of a 100 ng/mL matrix‑based standard produced an area %RSD of 1.93%, indicating good instrumental repeatability under the described conditions.
• Recovery and matrix performance: A PET sample spiked at 500 ng/g gave a measured final concentration equivalent to ~506.7 ng/mL (post‑processing), corresponding to a recovery of 101.4%, demonstrating accurate quantitation at that spike level. Unspiked PET blank showed no detectable BPA peak under the applied conditions.
• Chromatographic qualifiers: Both quantifier and qualifier ions were used to confirm identity at lower concentrations (e.g., 50 ng/mL), and extracted ion chromatograms showed clear peaks for the derivatized BPA standard and spiked samples.

Benefits and practical applications of the method

• Applicability: The workflow is suitable for routine screening and quantification of BPA in PET granules for quality control, recycling validation, and regulatory compliance when LOQ ~500 ng/g is acceptable.
• Simplicity and robustness: The extraction/derivatization protocol uses common solvents and reagents (THF, n‑hexane, BSTFA) and standard GC/MS hardware, offering a pragmatic approach for many laboratories without high‑end HRMS equipment.
• Good analytical performance: Demonstrated linear calibration, low instrument %RSD, and acceptable recovery at the tested spike level indicate method reliability for the tested matrix and conditions.

Future trends and potential improvements

• Increasing sensitivity: For lower LOQs, consider larger sample mass or concentration steps, use of isotopically labeled internal standards, or switching to tandem MS (GC‑MS/MS) or LC‑MS/MS to improve selectivity and sensitivity.
• Automated/green sample prep: Adoption of automated extraction, dispersive SPE cleanups, or solvent‑minimizing techniques could improve throughput and reduce solvent use.
• Matrix‑matched calibration and validation: Full validation (accuracy, precision, LOQ/LOD determination, matrix effects across diverse PET sources) would strengthen routine application and regulatory acceptance.
• Broader contaminant panels: Integration of multi‑residue workflows to screen other common PET contaminants (aldehydes, benzene, limonene, etc.) could improve laboratory efficiency and provide comprehensive safety data for rPET.

Conclusion

The described Agilent 8890/5977C GC/MS workflow combined with BSTFA derivatization provides a straightforward, repeatable method for identification and quantification of BPA in PET granules. The method yielded a calibration range of 10–500 ng/mL, an LOQ demonstrated at 500 ng/g in PET, strong repeatability (%RSD ~1.93% for replicate standards), and recoveries around 101% at the 500 ng/g spike. This protocol is suitable for routine laboratory testing where the demonstrated sensitivity meets regulatory or quality requirements.

Reference

1. Zhang, Y.; Tan, L. P. Analysis of Aldehydes, Benzene, and Limonene in Recycled Polyethylene Terephthalate Using Headspace GC/MS. Agilent Technologies application note, publication number 5994‑8063EN, 2024.
2. Food Safety and Standards Authority of India. Guidelines for Acceptance of Recycled Polyethylene Terephthalate (PET) as Food Contact Material (FCM‑rPET). Ministry of Health and Family Welfare, 2025.