Laser desorption sample transfer for gas chromatography/mass spectrometry

C. A. Seneviratne, S. Ghorai & K. K. Murray, Rapid Commun. Mass Spectrom. in press
DOI: 10.1002/rcm.7419

Schematic representation of the experimental configuration for laser desorption sample transfer to SPME fiber. The heated transfer line is held 1 mm above the sample surface and the SPME fiber is inserted into a tee in the tube and exposed to the flow.
Schematic representation of the experimental configuration for laser desorption sample transfer to SPME fiber. The heated transfer line is held 1 mm above the sample surface and the SPME fiber is inserted into a tee in the tube and exposed to the flow.

RATIONALE: 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 80 capture on a solid-phase microextraction (SPME) fiber for injection into a gas chromatography/mass spectrometry 81 (GCMS) system.

METHODS: 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 84 on a SPME fiber. The collected material was injected into a GC/MS instrument for analysis.

RESULTS: 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 87 standards, a mixture of nitroaromatic explosives, and collected cigarette smoke.

CONCLUSIONS: 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 90 1000 ng. Laser desorption ambient sampling of complex mixtures was accomplished using SPME GC/MS.