If there is a reaction being carried out in an Ar atmosphere and M41 is the characteristic m/z of a target product while H2 is a by-product (such as chemical or electrochemical partial-reduction of propyne to propene), the production of an M41-corresponding analyte would make the M41 product being produced (e.g. propene) appear artificially high, thus distorting any analysis. When the reduced ionization energy (28 eV) was switched to the standard higher ionization energy (70 eV) in the Ar atmosphere, M41 also showed an increase (Figure ) similar to what is shown in Figure . This suggests that the occurrence of Chem-I between H2 and Ar is independent of applied EI energy.