ASTM D7675-22

5.1?Low operating temperature fuel cells such as proton exchange membrane fuel cells (PEM-FC) require high purity hydrogen for maximum material performance and lifetime. Analysis to 0.1 part per million (ppm(v)) concentration of THCs (measured as CH₄) in hydrogen is necessary for ensuring a feed gas of sufficient purity to satisfy fuel cell system needs as defined in SAE J2719 or as specified in regulatory codes.

5.2?Dynamic dilution techniques using highly accurate mass flow controllers can be used with test samples that have THC content exceeding the upper limit of the instruments linear range, without the need to recalibrate the instrument using higher levels of calibration standards. The sample can be diluted with a high purity grade of hydrogen (99.999 %, so long as it contains < 0.1 ppm(v) THCs) to achieve a result of the THC content by applying the appropriate dilution factor to the result. Samples that contain THC concentrations greater than 1000 ppm(v) may be determined, although results will likey be achieved with reduced precision and should be analyzed by the dilution method.

5.3?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 THC content determination. This can be achieved by using a zero gas and a calibration gas that consist of the same background gas as the actual sample. As an example, for the THC determination of nitrogen, the instrument zero point must be determined with a high purity grade of nitrogen (99.999 % and < 0.1 ppm(v) THCs) and the instrument calibration must be done with a certified standard of CH_{1.1?This test method describes a procedure for total hydrocarbons (THCs) measurement in hydrogen intended as a fuel on a methane (C1.2?This test method is a Flame Ionization Detector-based (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.}