Objective To establish a gas chromatography-mass spectrometry (GC-MS) method for the qualitative and quantitative analysis of eight common siloxanes in biomethane, addressing the need for product quality control.

Method A DB-5MS capillary column was employed, achieving complete separation of the siloxane components through an optimized temperature program. Detection was performed using a single quadrupole mass spectrometer.Qualitative analysis was conducted by matching against the National Institute of Standards and Technology mass spectral library and retention time, while quantitative analysis was performed using the external standard method. The developed method was systematically evaluated for its limit of detection (LOD), repeatability, and accuracy, and subsequently applied to the analysis of actual biomethane samples.

Result The method demonstrated high sensitivity, with LODs for the eight siloxanes ranging from 0.17×10⁻⁹ to 5.35×10⁻⁹. Excellent repeatability was observed, with relative standard deviations for seven consecutive measurements ranging from 1.7% to 3.4%. The accuracy met the requirements for trace analysis, as relative deviations between measured and certified reference values were controlled within −14.6% to 11.1%. The proposed method successfully detected D3 and D5 in real biomethane samples.

Conclusion The established analytical method is sensitive, accurate, and reliable. It provides an effective technical solution for detecting trace siloxane content in biomethane, offering crucial support for ensuring product quality and the safe operation of downstream equipment.