A method of detecting specific gas species in an ion trap, the specific gas species initially being a trace component of a first low concentration in a volume of gas, the method comprising: i) ionizing the gas including the specific gas species, thereby creating specific ion species; ii) producing an electrostatic potential in which the specific ion species are confined in the ion trap to trajectories, at natural oscillation frequencies, in an electrode structure that includes first and second opposed mirror electrodes and a central lens electrode therebetween; iii) exciting confined specific ion species with an AC excitation source having an excitation frequency; iv) scanning the excitation frequency of the AC excitation source to eject the specific ion species from the ion trap; and v) detecting the ejected specific ion species, the method further comprising increasing the concentration of the specific ion species within the ion trap relative to the first low concentration prior to scanning the excitation frequency that ejects the ions of the specific gas species; characterized in that the method further comprises increasing the concentration of the specific gas species by either: a) selective removal of gas species other than the specific gas species by selective sorption of the gas species other than the specific gas species with a non-evaporable getter; or b) selective sorption of the specific gas species with a non-evaporable getter, followed by desorption of the specific gas species from the non-evaporable getter. i) ionizing the gas including the specific gas species, thereby creating specific ion species; ii) producing an electrostatic potential in which the specific ion species are confined in the ion trap to trajectories, at natural oscillation frequencies, in an electrode structure that includes first and second opposed mirror electrodes and a central lens electrode therebetween; iii) exciting confined specific ion species with an AC excitation source having an excitation frequency; iv) scanning the excitation frequency of the AC excitation source to eject the specific ion species from the ion trap; and v) detecting the ejected specific ion species, the method further comprising increasing the concentration of the specific ion species within the ion trap relative to the first low concentration prior to scanning the excitation frequency that ejects the ions of the specific gas species; characterized in that the method further comprises increasing the concentration of the specific gas species by either: a) selective removal of gas species other than the specific gas species by selective sorption of the gas species other than the specific gas species with a non-evaporable getter; or b) selective sorption of the specific gas species with a non-evaporable getter, followed by desorption of the specific gas species from the non-evaporable getter. a) selective removal of gas species other than the specific gas species by selective sorption of the gas species other than the specific gas species with a non-evaporable getter; or b) selective sorption of the specific gas species with a non-evaporable getter, followed by desorption of the specific gas species from the non-evaporable getter.