As 𝛾 𝑖 is a function not only of temperature and pressure, but also of the mole fractions of all other components, it can be said that the vapor pressure of a compound (and therefore it's headspace concentration) is dependent on the it's concentration in the liquid phase, and of the liquid phase composition overall, including those components with a low vapor pressure. Furthermore, as the experiment progresses, and due to the incongruent evaporation, the headspace concentrations of the components can evolve in complicated ways. Lastly, due to the finite amount of charge imparted onto compounds in the APCI source, and the propensity for competitive ionisation leading to ion suppression and enhancement, or adduct formation, depending on the composition of the vapour phase, this may further make characteristic the profile of a compound's gas phase concentration, and may be used as a further authentication method.