Ion mobility spectrometer and method for operating the same

A method for operating an ion mobility spectrometer to determine an ion mobility of a sample, the method comprising:

• setting first operating parameters of at least one of a local ionisation source, a drift gas supply for supplying air as drift gas, and a sample gas supply of the ion mobility spectrometer for generating NOX ions at the local ionisation source and for introducing the generated NOX ions into a drift chamber of the ion mobility spectrometer;
• measuring a first drift time tNOX of the NOX ions at the drift chamber temperature T;
• setting second operating parameters of at least one of the local ionisation source, the drift gas supply, and the sample gas supply to generate sample ions without formation of NOX ions at the local ionisation source and/or to avoid the introduction of NOX ions into the drift chamber;
• measuring a second drift time tP of the sample ions at the drift chamber temperature T;
• and
• determining a normalised ion mobility of the sample K0P(T) using the measured first drift time tNOX, the measured second drift time tP, and a normalised ion mobility of the NOX ions K0R(T) as reference according to K0P(T)=tNOX/tP*K0R(T).