ASTM D7675-11

Low operating temperature fuel cells such as proton exchange membrane fuel cells (PEFCs) require high purity hydrogen for maximum material performance and lifetime. Analysis to 0.1 part per million (ppm) concentration of total hydrocarbons (measured as methane) in hydrogen is necessary for assuring a feed gas of sufficient purity to satisfy fuel cell system needs as defined in SAE TIR J2719 or as specified in regulatory codes.

Although not intended for application to gases other than hydrogen, techniques within this test method can be applied to other non-hydrocarbon gas samples requiring total hydrocarbon content determination.

1.1 This test method describes a procedure for total hydrocarbons (THC) measurement in hydrogen intended as a fuel for fuel cells on a C1 Basis. Total Hydrocarbons on a C1 basis is an analytical technique where total carbon is determined and all of the hydrocarbons are assumed to have the same response as Methane. Sensitivity from 0.1 part per million (ppm, µmole/mole) up to 1000 parts per million (ppm, µmole/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.

1.2 This test method is a FID based hydrocarbon analysis method without the use of separation columns, therefore, this method does not provide speciation of individual hydrocarbons. Varieties of instruments are manufactured and can be used for this method.

1.2.1 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. Therefore C2 and above hydrocarbons are quantified relative to the number of carbon atoms present in the molecule.

1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.