(i) the molecular ion peak (𝑀 "⋅ ) is contained in the spectrum, (ii) the abundance of 𝑀 "⋅ is greater than some minimum abundance (𝜖 $ ), (iii) peaks with mass greater than 𝑀 "⋅ must be explainable as isotope peaks, and (iv) nearby peaks with mass less than 𝑀 "⋅ must not be a result of "illogical" neutral losses