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:

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hexamethyldisiloxane (L2);

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octamethyltrisiloxane (L3);

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decamethyltetrasiloxane (L4);

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dodecamethylpentasiloxane (L5);

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hexamethylcyclotrisiloxane (D3);

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octamethylcyclotetrasiloxane (D4);

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decamethylcyclopentasiloxane (D5);

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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 %.