Ambient Infrared Laser Ablation Mass Spectrometry (AIRLAB-MS) of Live Plant Tissue with Plume Capture by Continuous Flow Solvent Probe

Abstract

A new experimental setup for spatially resolved ambient infrared laser ablation-mass spectrometry (AIRLAB-MS) that uses an infrared microscope with an infinity-corrected reflective objective and a continuous flow solvent probe coupled to a Fourier transform ion cyclotron resonance mass spectrometer is described. The efficiency of material transfer from the sample to the electrospray ionization emitter was determined using glycerol/methanol droplets containing 1 mM nicotine and is ∼50%. This transfer efficiency is significantly higher than values reported for similar techniques. Laser desorption does not induce fragmentation of biomolecules in droplets containing bradykinin, leucine enkephalin and myoglobin, but loss of the heme group from myoglobin occurs as a result of the denaturing solution used. An application of AIRLAB-MS to biological materials is demonstrated for tobacco leaves. Chemical components are identified from the spatially resolved mass spectra of the ablated plant material, including nicotine and uridine. The reproducibility of measurements made using AIRLAB-MS on plant material was demonstrated by the ablation of six closely spaced areas (within 2 × 2 mm) on a young tobacco leaf, and the results indicate a standard deviation of <10% in the uridine signal obtained for each area. The spatial distribution of nicotine was measured for selected leaf areas and variation in the relative nicotine levels (15–100%) was observed. Comparative analysis of the nicotine distribution was demonstrated for two tobacco plant varieties, a genetically modified plant and its corresponding wild-type, indicating generally higher nicotine levels in the mutant