Analysis of natural gas - Silicon content of biomethane - Part 1: Determination of total silicon by atomic emission spectroscopy (AES) (ISO/FDIS 2613-1:2023)
This document is applicable to the determination of the total silicon content in gaseous matrices such as biomethane, biogas and landfill gas. Silicon is present in a gas phase contained predominantly in siloxane compounds, trimethylsilane and trimethylsilanol. The analytical form of the silicon measured in liquid phase after conducted sampling and derivatization procedure is soluble hexafluorosilicate anion stable in slightly acidified media. Total silicon is expressed as a mass of silicon in the volume of the analysed gas. This document is applicable to all stated gas matrices with silicon concentrations up to 5 mg/m3, and it is prevalently intended for the biomethane matrices containing (0,1 to 0,5) mg/m3. It can be used for higher concentration but then the absorption efficiency of the bubblers/impingers should be checked before the results can be regarded as valid. The detection limit of the method is estimated as 0,05 mg/m3 based on a sample volume of 0,020 m3. All compounds present in the gas phase are volatile at the absorption and derivatization temperature and gaseous siloxanes are trapped in absorbance media and derivatized into analytical silicon specie are measured by this method. The concentration of the silicon is measured in diluted derivatization media using atomic emission spectrometer upon atomisation/ionisation in microwave or inductively coupled plasma.