This document describes a gas chromatography – ion mobility spectroscopy (GC-IMS) method for the determination of the concentration of siloxanes in biomethane. The method is applicable to the following siloxanes:

—     hexamethyldisiloxane (L2);

—     octamethyltrisiloxane (L3);

—     decamethyltetrasiloxane (L4);

—     dodecamethylpentasiloxane (L5);

—     hexamethylcyclotrisiloxane (D3);

—     octamethylcyclotetrasiloxane (D4);

—     decamethylcyclopentasiloxane (D5);

—     dodecamethylcyclohexasiloxane (D6).

This document describes suitable calibration and measurement strategies to quantify siloxanes in (bio)methane around and above the 0,3 mg m^-3 (14 µmol mol^-1) level and applies to analyses within absolute pressure ranges of 1 bar – 2 bar, temperatures of 0 °C – 40 °C and relative humidity < 90 %.