An ion drift-chemical ionization mass spectrometry (ID-CIMS) technique has been developed to detect andquantify trace gases, including volatile organic compoundsand inorganic species. The trace species are chemicallyionized into positive or negative product ions with a well-controlled ion−molecule reaction time. The ID-CIMSmethod allows for quantification of the trace gases withoutthe necessity of performing calibrations with authenticstandards for the trace gases. Demonstrations of theability of ID-CIMS to accurately quantify isoprene andHNO3 in a laboratory setting are presented. The resultsillustrate that the ID-CIMS technique facilitates detectionand quantification of organic and inorganic species inlaboratory kinetic investigations and field measurements.