A portable system (10) is disclosed for collecting a sample from exhaled breath of a subject. Drug substance in the exhaled breath are detected or determined. The sample is collected for further analysis using mass-spectroscopy. The system comprises a sampling unit (14) and a housing (12) arranged to hold the sampling unit (14), the sampling unit (14) is adapted to collect non-volatile and volatile compounds of the at least one drug substance from the exhaled breath from the subject. The housing (12) has at least one inlet (15) for the subject to exhale into the housing (12) to the sampling unit (14) and at least one outlet (16) for the exhaled breath to exit through.
