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