Laser ablation coupled to a flowing atmospheric pressure afterglow for ambient mass spectral imaging.
A plasma-based ambient desorption/ionization mass spectrometry (ADI-MS) source was used to perform molecular mass spectral imaging. A small amount of sample material was ablated by focusing 266 nm laser light onto a spot. The resulting aerosol was transferred by a nitrogen stream to the flowing afterglow of a helium atmospheric pressure glow discharge ionization source; the ionized sample material was analyzed by a Leco Unique time-of-flight mass spectrometer. Two-dimensional mass spectral images were generated by scanning the laser beam across a sample surface. The total analysis time for a 6 mm (2) surface, which is limited by the washout of the ablation chamber, was less than 30 min. With this technique, a spatial resolution of approximately 20 microm has been achieved. Additionally, the laser ablation configuration was used to obtain depth information of over 2 mm with a resolution of approximately 40 microm. The combination of laser ablation with the flowing atmospheric pressure afterglow source was used to analyze several sample surfaces for a wide variety of analytes and with high sensitivity (LOD of 5 fmol for caffeine).
Shelley
Jacob T
JT
Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
Ray
Steven J
SJ
Hieftje
Gary M
GM
D001274:Atmospheric Pressure; D007834:Lasers; D013058:Mass Spectrometry / Q000295:instrumentation* / Q000379:methods*; D015394:Molecular Structure; D013696:Temperature