Laser desorption sample transfer for gas chromatography/mass spectrometry.

Ambient mass spectrometry can detect small molecules directly, but complex mixtures can be a challenge. We have developed a method that incorporates small molecule separation based on laser desorption with capture on a solid-phase microextraction (SPME) fiber for injection into a gas chromatography/mass spectrometry (GC/MS) system. Samples on a metal target were desorbed by a 3 µm mid-infrared laser focused to a 250 µm spot and 1.2 mJ pulse energy. The desorbed material was aspirated into a metal tube suspended 1 mm above the laser spot and captured on a SPME fiber. The collected material was injected into a GC/MS instrument for analysis. We have developed a versatile approach for ambient laser desorption sampling onto SPME for GC/MS analysis. The performance of the laser desorption SPME capture GC/MS system was demonstrated for small molecule standards, a mixture of nitroaromatic explosives, and collected cigarette smoke. The utility of ambient laser desorption sampling onto SPME for GC/MS was demonstrated. The performance of the method was evaluated by preparing calibration standards of caffeine over a range from 200 to 1000 ng. Laser desorption ambient sampling of complex mixtures was accomplished using SPME GC/MS.