Depending on the GC being used, the required amount of gas sample varies, but typically around 100 µL are sufficient. It is advantageous to perform a four-point calibration with a reference gas containing H2 (ideally in argon) before measuring the sample to ensure accurate quantification. Details on the calibration procedure can be found in the Supplementary Section 3. Also, sample measurements should be carried out in duplicate or triplicate to ensure accuracy and reproducibility.