ASTM International

Standard Test Method for Determination of Total Hydrocarbons in Hydrogen by FIDBased Total Hydrocarbon (THC) Analyzer
 N D7675

Annotation

This test method describes a procedure for total hydrocarbons (THC) measurement in hydrogen intended as a fuel for fuel cells on a methane (C1) basis. The determination of total hydrocarbons on a C1 basis is an analytical technique where all of the hydrocarbons are assumed to have the same response as methane. Sensitivity from 0.1 part per million (ppm(v), mole/ mole) up to 1000 parts per million (ppm(v), mole/mole) concentration are achievable. Higher concentrations can be analyzed using appropriate dilution techniques. This test method can be applied to other gaseous samples requiring analysis of trace constituents provided an assessment of potential interferences has been accomplished.

This test method is an FID-based hydrocarbon analysis method without the use of separation columns. Therefore, this method does not provide speciation of individual hydrocarbons. Several varieties of instruments are manufactured and can be used for this method.

This method provides a measure of total hydrocarbons “as methane,” because all hydrocarbon species are quantified the same as methane response, which is the sole species used for calibration. Magnitude of the FID response to an atom of carbon is dependent on the chemical environment of this atom in the molecule. This method provides the total hydrocarbon result as if all carbon atoms are from aliphatic, aromatic, olefinic, or acetylenic compounds, where the detector response caused by these atoms are approximately relative to the number of carbon atoms present in the molecule. Other types of molecules, including those containing oxygen or chlorine atoms will respond differently and usually much lower than the corresponding aliphatic hydrocarbon. Therefore other methods (Test Methods D7653, D7892, or equivalent) must be utilized to determine the exact constituents of the total hydrocarbon response determined by this method.