Unattended Quantitative Determination of VOCs in Food Packaging Samples Using a Robotic Sampler for Standard Addition and Analysis

Significance of topic

The analysis of volatile organic compounds (VOCs) in food packaging is essential to ensure consumer safety and regulatory compliance. Headspace sampling combined with gas chromatography–mass spectrometry (GC–MS) is a standard approach, but manual sample preparation can be laborious and susceptible to error. Automating both the dilution and standard addition steps promises to improve throughput and reproducibility, particularly when dealing with complex solid matrices where matrix effects complicate quantification.

Objectives and Study Overview

This study explores the feasibility of a fully unattended, quantitative headspace GC–MS method for VOC determination in packaging materials. A robotic autosampler performs automated standard additions directly in the sampling sequence, addressing matrix-induced biases without manual intervention. The workflow was tested using mixtures of common residual solvent standards and a real croissant packaging sample.

Methodology

• Standard solution preparation: Two residual solvent mixtures from Sigma-Aldrich were combined and diluted 1:1000 in water.
• Automated standard addition: The TriPlus RSH autosampler delivered variable volumes (1–7 µL) of standard into empty vials, compensating with water to maintain constant volume.
• Sample vials: Packaging film from a commercial croissant was cut into 48 cm² pieces and placed in headspace vials; five vials were prepared for standard addition levels.
• Headspace conditions: Incubation at 80 °C for 15 min; 1000 µL sample loop; syringe at 120 °C; split injection.
• Chromatographic separation: TRACE 1310 GC with TG-624 capillary column (60 m × 0.25 mm, 1.4 µm); single quadrupole ISQ MS detection.
• Detection modes: Total ion current for compound identification and selected ion monitoring (SIM) at m/z 31, 43, 45, 55, 56, 59, 91.

Used Instrumentation

• Thermo Scientific TriPlus RSH robotic autosampler
• Thermo Scientific TRACE 1310 Gas Chromatograph
• Thermo Scientific ISQ single quadrupole mass spectrometer
• Thermo Scientific Xcalibur software (version 2.1)
• TraceGOLD TG-624 capillary column

Main Results and Discussion

The automated standard addition approach yielded excellent linearity (R² > 0.999 for 1-propanol and isopropyl acetate) across the 1–7 µL addition range. Limits of quantification were below 0.01 mg/m² for most VOCs, with slightly higher values for ethanol, tetrahydrofuran, and ethoxy ethanol. In the real packaging sample, 2-propanol 1-methoxy and 1-propanol emerged as the predominant residual solvents, each under 0.1 mg/m². Other detected VOCs were quantified at or below 0.01 mg/m². Automated dilution and addition reduced manual variability and error.

Benefits and Practical Applications

• Enhanced throughput by integrating sample preparation and analysis in a single sequence.
• Improved quantification accuracy in complex matrices via automated standard addition.
• Reduced labor and error by eliminating manual dilution steps.
• Sensitivity sufficient for trace-level residual solvent monitoring in packaging compliance.

Future Trends and Possibilities for Application

• Expansion to broader classes of analytes such as semi-volatiles or flavor compounds.
• Integration with high-resolution mass spectrometry for comprehensive screening.
• Application in other fields: pharmaceuticals, environmental monitoring, and materials testing.
• Advancements in software-driven decision making for real-time compliance reporting.

Conclusion

A fully unattended headspace GC–MS workflow employing robotic standard addition demonstrates reliable quantification of VOCs in food packaging. The method achieves high linearity, low quantification limits, and reduced operator intervention. This approach can streamline quality control processes and support regulatory compliance in the packaging industry.