Continuous Flow Atmospheric Pressure Laser Desorption/Ionization Using a 6–7-µm-Band Mid-Infrared Tunable Laser for Biomolecular Mass Spectrometry

Abstract

A continuous flow atmospheric pressure laser desorption/ionization technique using a porous stainless steel probe and a 6–7-µm-band mid-infrared tunable laser was developed. This ion source is capable of direct ionization from a continuous flow with a high temporal stability. The 6–7-µm wavelength region corresponds to the characteristic absorption bands of various molecular vibration modes, including O–H, C=O, CH3 and C–N bonds. Consequently, many organic compounds and solvents, including water, have characteristic absorption peaks in this region. This ion source requires no additional matrix, and utilizes water or acetonitrile as the solvent matrix at several absorption peak wavelengths (6.05 and 7.27 µm, respectively). The distribution of multiply-charged peptide ions is extremely sensitive to the temperature of the heated capillary, which is the inlet of the mass spectrometer. This ionization technique has potential for the interface of liquid chromatography/mass spectrometry (LC/MS).

Carbonized Hybrid Micro/Nanostructured Metasurfaces Produced by Femtosecond Laser Ablation in Organic Solvents for Biomimetic Antireflective Surfaces

“…The NIR–MIR reflectance spectrum of CuZn exhibits numerous small peaks at 2.92, 3.38–3.44, 4.58, 5.22, 5.76, 6.35, 7.04, 7.90, and 8.56 μm (Figure h) corresponding to wavenumbers of 3424, 2959–2906, 2183, 1915, 1736, 1574, 1266, and 1168 cm –1 . These are associated with adsorbed −OH, CH x , CO, NO, CH, carboxylate anions, the degenerated bending vibration of CH 3 , the asymmetric stretching mode of the carbonate O–C–O group, and the rocking mode of CH 3 groups generated during FLAMOS. These peaks provide additional evidence for the occurrence of the coking process.…”

Substrate-Mediated Laser Ablation under Ambient Conditions for Spatially-Resolved Tissue Proteomics

“…Desorption and ionization can also be decoupled when molecules are first ejected, and then captured and subsequently ionized. The capture is commonly achieved by a spray of charged solvent droplets that are delivered under ESI conditions, allowing for direct analysis of the sampled material by MS. Techniques using this procedure are Laser Desorption Electrospray Ionization (LDESI) 8 9 , Matrix-Assisted Laser Desorption Electrospray Ionization (MALDESI) 10 11 , Electrospray Laser Desorption Ionization (ELDI) 12 , Laser Electrospray Mass Spectrometry (LEMS) 13 14 or Laser Ablation Electrospray Ionization (LAESI) 15 . Alternatively, ejected molecules can be captured into neutral solvent droplets followed by indirect MS analysis for Laser Ablation/Droplet Capture (LADC) 16 17 18 19 or be captured by a continuous flow of solvent for direct MS analysis 20 21 .…”