Hydrocarbons, C1 – C8 - Analysis of air sample

Significance of the topic

Volatile hydrocarbons in ambient air influence air quality, human health and climate chemistry. A robust analytical method for separating and quantifying C1–C8 hydrocarbons enables environmental agencies and research laboratories to monitor pollutant levels, track emission sources and assess compliance with regulatory standards.

Objectives and study overview

This application note demonstrates gas chromatographic separation of 38 C1–C8 hydrocarbons in a 350 mL air sample collected at Bilthoven, The Netherlands. The aim is to achieve baseline resolution of light aliphatic and aromatic hydrocarbons within a 28 min runtime, covering a concentration range from low trace levels up to 14 µg/m3.

Methodology and instrumentation

Technique and column

• Capillary gas chromatography using an Agilent CP-Al2O3/KCl PLOT column (0.53 mm × 25 m, 10 µm film thickness)

Carrier gas and injector

• Helium at 40 kPa
• VOC-Air injector for direct air sampling

Detector

• Flame ionization detector at 275 °C for universal hydrocarbon response

Temperature program

• 50 °C initial, ramp to 75 °C at 5 °C/min
• Ramp to 125 °C at 10 °C/min
• Ramp to 200 °C at 15 °C/min, hold to 30 min total

Sample size and range

• 350 mL ambient air
• Quantitation from 0.02 to 14 µg/m3 for target analytes

Main results and discussion

The method achieved clear separation of 38 hydrocarbons, including methane fragments, alkenes, alkynes, cycloalkanes and aromatics, within 28 min. Early eluting species such as ethane and ethylene were resolved under low-temperature conditions, while higher-boiling compounds like toluene and xylenes eluted during the final temperature ramp. Peak shapes and retention time reproducibility met quality criteria for environmental analysis. No coelutions were observed among isomeric pairs such as cis-2-pentene versus trans-2-pentene.

Benefits and practical applications

• Comprehensive profiling of C1–C8 hydrocarbons in a single run improves laboratory throughput
• Low detection limits enable ambient monitoring at trace levels
• Robust column chemistry ensures consistent performance for routine environmental surveillance
• Applicability to urban, industrial and remote site investigations

Future trends and possibilities

Ongoing advances include coupling PLOT columns with mass spectrometric detectors for enhanced selectivity and identification of unknowns. Miniaturized sampling devices and portable GC systems may allow field-deployable hydrocarbon monitoring. Data science tools can integrate long-term datasets for source apportionment and trend analysis.

Conclusion

The described capillary GC method successfully separates and quantifies a broad range of C1–C8 hydrocarbons in ambient air within a 28 min analysis. Its sensitivity, resolution and reproducibility make it a valuable tool for environmental and industrial air quality monitoring.

Reference

Agilent Technologies Inc. Application Note: Hydrocarbons, C1–C8 Analysis of Air Sample. First published prior to 11 May 2010, printed October 30, 2015.