The world's smallest GC-ITMS instrument is fast, accurate, and reliable. The system features a low thermal mass gas chromatograph with ballistic temperature programming and a toroidal ion trap mass spectrometer with mass range from 50 to 400 Daltons. Samples are injected using a novel SPME fiber custody syringe. The system weighs less than 20 pounds, is battery operated, and hand-portable. This miniature GC-ITMS system is ideal for rapid (~3 min) screening of chemical agents, explosives, and hazardous substances.