Trace sulfur and hydrocarbon contaminants in beverage grade carbon dioxide

Significance of the Topic

Beverage-grade carbon dioxide is a critical component in the production of carbonated drinks. Even trace levels of sulfur gases or hydrocarbons can affect taste, safety, and shelf life. Ensuring the high purity of CO2 prevents consumer health issues and maintains product quality in food and beverage industries.

Objectives and Overview of the Study

This work describes the development of a gas chromatography (GC) method capable of detecting sulfur gases (hydrogen sulfide, carbonyl sulfide, sulfur dioxide) at approximately 0.1 ppm and trace hydrocarbons (acetaldehyde, benzene, light hydrocarbons) down to sub-ppbv levels in beverage-grade CO2. A dual-analysis approach integrates direct injection for sulfur compounds and preconcentration for hydrocarbons.

Methodology and Used Instrumentation

A two-task GC setup was employed:

• Pulsed flame photometric detector (PFPD) for sulfur gases, using a capillary column (CP-SilicaPLOT, 0.32 mm × 30 m), helium carrier at 2 mL/min, and a 100 µL direct injection.
• Sample preconcentration trap (SPT) for hydrocarbons, loading 100 mL of CO2 onto Tenax TA at ambient temperature, followed by thermal desorption (190 °C) to a PoraPLOT Q capillary column (0.53 mm × 30 m) and detection by FID.

All sample lines utilized deactivated Silcosteel to minimize adsorption, especially of H2S.

Main Findings and Discussion

• Sulfur gases were resolved at ~0.2 ppm with retention time precision below 0.5 %RSD and area precision under 6.5 %RSD at 1 ppm.
• Preconcentration of hydrocarbons achieved detection of aromatics (benzene, toluene, ethylbenzene, o-xylene) at 50 ppbv with area precision ~1.2 %RSD and retention time below 0.02 %RSD.
• Acetaldehyde was measured at 0.5 ppmv following the same trap and thermal desorption protocol.

These results demonstrate reliable quantitation of both classes of contaminants in a single GC system with suitable sensitivity for industry requirements.

Benefits and Practical Applications

• Supports quality control in beverage production by verifying CO2 purity.
• Enables rapid screening for odor‐ or taste‐impacting sulfur compounds and health‐relevant hydrocarbons.
• Reduces risk of consumer complaints and product recalls by early detection of trace contaminants.

Future Trends and Potential Applications

Advances may include automated sample handling, integration with mass spectrometric detectors for expanded analyte coverage, and real‐time monitoring systems for continuous CO2 quality assurance. Adaptation of similar protocols to other industrial gases and compressed air systems could further broaden applications.

Conclusion

The described GC method, combining direct injection PFPD analysis for sulfur gases and preconcentration–FID analysis for hydrocarbons, provides a robust, sensitive, and practical solution for monitoring trace contaminants in beverage‐grade CO2. This dual approach meets industry demands for safety, quality, and regulatory compliance.

References

No specific literature references were provided in the original application note.