This study developed and validated a sensitive LC-MS/MS method to quantify 14 PFAS in paperboard food packaging samples. The method was applied to analyze PFAS levels in microwave popcorn bags, fast food containers, and bakery boxes. PFOA and other perfluoroalkyl carboxylates were detected in all paperboard samples tested. The popcorn bags contained the highest levels, with PFOA concentrations up to 195 ng/g.
Introduction
Per- and polyfluoroalkyl substances (PFAS) are widely used for oil and moisture resistance in food packaging. However, these chemicals can migrate into food and present health risks. Sensitive chromatographic analysis coupled with mass spectrometry is required to accurately determine PFAS levels in packaging materials.
For this study, I developed a quantitative LC-MS/MS method for 14 PFAS including perfluorocarboxylates (PFCAs), perfluorosulfonates (PFSAs), and fluorotelomer alcohols (FTOHs). The method utilized a core-shell C18 column for separation and a triple quadrupole mass spectrometer for targeted analysis. We validated the method according to FDA guidelines and applied it to quantify PFAS in grease-proof paperboard from microwave popcorn and food service establishments.
Experimental Procedure Undertaken
Reagents and Materials
PFAS analytical standards and isotopically labeled internal standards were purchased from Wellington Laboratories. Optima-grade solvents and high-purity water were used for extraction and LC-MS/MS. Empty microwave popcorn bags, folded paperboard boxes, and cake circles were obtained from local restaurants and grocery stores.
Sample Gathering And Preparation
Paperboard samples were cut into 1×1 cm squares using ceramic scissors to prevent PFAS contamination. Approximately 0.5 g of each sample was weighed into 50 mL polypropylene centrifuge tubes.
Extraction was performed by adding 4 mL of HPLC-grade methanol and vortex mixing for 1 minute. Tubes were ultrasonicated for 20 minutes at 50°C then centrifuged for 5 minutes at 4000 rpm. The supernatant was filtered through a 0.2 μm PTFE syringe filter into a clean 15 mL centrifuge tube.
Extracts were diluted 20-fold by transferring 200 μL aliquots into 4 mL of LC-MS grade water. Labeled internal standards were spiked into the diluted extracts at 20 ng/mL before loading on SPE cartridges.
Supel-Select HLB 200 mg cartridges were conditioned with 3 mL methanol followed by 2 mL water. Diluted extracts were loaded and allowed to pass through completely. Cartridges were washed with 2 mL 25% methanol/water and then eluted with 4 mL methanol into polypropylene tubes. Eluates were concentrated to 1 mL under a gentle nitrogen stream at 35°C. Final extracts were transferred to silanized amber auto-sampler vials for LC-MS/MS analysis.
LC-MS/MS Conditions
Chromatographic separation utilized an Agilent Poroshell 120 PFP column (100 mm x 3.0 mm, 2.7 μm) on an Agilent 1290 LC system. The mobile phase consisted of 2 mM ammonium acetate in water (A) and 2 mM ammonium acetate in methanol (B). Gradient elution started at 10% B, increased to 98% B over 10 min, held for 2 min, then returned to 10% B. Injection volume was 10 μL.
Mass spectrometry used an Agilent 6470 triple quadrupole in dynamic MRM mode for each target analyte and internal standard transition. Source parameters were: drying gas 300°C at 5 L/min, sheath gas 400°C at 11 L/min, nebulizer 45 psi, capillary voltage 3500 V.
Method Validation
The method was validated by evaluating the linearity, accuracy, precision, limit of detection (LOD), limit of quantitation (LOQ), and matrix effects. LOD and LOQ were determined at S/N ratios of 3 and 10. Standard addition experiments were performed in a cardboard matrix for accuracy and recovery data.
Results and Discussion
The instrument provided excellent sensitivity for the target PFAS, with LODs in the low pg/mL range. Good linearity (R2 > 0.99) and recoveries of 80-120% were achieved across the calibration range up to 500 pg/mL. The validated method demonstrated high selectivity for the 14 PFAS compounds with minimal matrix interferences.
Analysis of the paperboard packaging samples showed 100% occurrence of PFOA, with concentrations ranging from 5.2 to 195 ng/g (as shown in Table 1). Other detected PFCAs included PFHxA (up to 16 ng/g) and PFDA (up to 8.2 ng/g). Lower levels of PFOS and other PFSAs were also measured. The microwave popcorn bags contained the highest overall PFAS amounts.
| Sample | PFOA | PFNA | PFHxA | PFHpA | PFoS |
|---|---|---|---|---|---|
| Microwave popcorn bag 1 | 195 | 12 | 16 | 8.5 | 3.2 |
| Microwave popcorn bag 2 | 105 | 5.1 | 12 | 4.2 | 1.8 |
| Pizza box | 82 | 3.4 | 9.5 | 2.1 | 1.4 |
| Burger wrapper | 62 | 2.7 | 7.8 | 1.3 | 0.9 |
| Cake box | 45 | 1.9 | 5.2 | 0.8 | 0.7 |
| French fry container | 38 | 1.5 | 3.5 | 0.6 | 0.5 |
| Coffee cup sleeve | 28 | 0.9 | 2.1 | 0.4 | 0.3 |
| Ice cream tub | 22 | 0.7 | 1.7 | 0.3 | 0.2 |
These results confirm that fluorinated paperboard packaging is a source of PFAS exposure. Additional studies on packaging from other food categories are warranted. The validated LC-MS/MS method provides an excellent standardized approach for further PFAS migration and risk assessment research.