TY - JOUR
T1 - Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture/Electrospray Ionization
AU - Cahill, John F.
AU - Kertesz, Vilmos
AU - Ovchinnikova, Olga S.
AU - Van Berkel, Gary J.
N1 - Publisher Copyright:
© 2015 American Society for Mass Spectrometry (outside the USA).
PY - 2015/9/8
Y1 - 2015/9/8
N2 - Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed noncontact liquid-vortex capture probe has been used to efficiently collect material ablated by a 355 nm UV laser in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appears to be classic electrospray ionization spectra; however, the 'softness' of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. In this work, a series of benzylpyridinium salts were employed as thermometer ions to compare internal energy distributions between electrospray ionization and the UV laser ablation/liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. These data, along with results from the analysis the biological molecules bradykinin and angiotensin III indicated that the ions or their fragments formed directly by UV laser ablation that survive the liquid capture/electrospray ionization process were likely to be an extremely small component of the total ion signal observed. Instead, the preponderate neutral molecules, clusters, and particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream, then electrosprayed, were the principal source of the ion signal observed. Thus, the electrospray ionization process used controls the overall 'softness' of this technique. [Figure not available: see fulltext.]
AB - Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed noncontact liquid-vortex capture probe has been used to efficiently collect material ablated by a 355 nm UV laser in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appears to be classic electrospray ionization spectra; however, the 'softness' of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. In this work, a series of benzylpyridinium salts were employed as thermometer ions to compare internal energy distributions between electrospray ionization and the UV laser ablation/liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. These data, along with results from the analysis the biological molecules bradykinin and angiotensin III indicated that the ions or their fragments formed directly by UV laser ablation that survive the liquid capture/electrospray ionization process were likely to be an extremely small component of the total ion signal observed. Instead, the preponderate neutral molecules, clusters, and particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream, then electrosprayed, were the principal source of the ion signal observed. Thus, the electrospray ionization process used controls the overall 'softness' of this technique. [Figure not available: see fulltext.]
KW - Electrospray ionization
KW - Internal energy
KW - Laser ablation
KW - Liquid capture
KW - Mass spectrometry imaging
KW - Surface sampling
KW - Thermometer ions
UR - http://www.scopus.com/inward/record.url?scp=84938795829&partnerID=8YFLogxK
U2 - 10.1007/s13361-015-1195-x
DO - 10.1007/s13361-015-1195-x
M3 - Article
AN - SCOPUS:84938795829
SN - 1044-0305
VL - 26
SP - 1462
EP - 1468
JO - Journal of the American Society for Mass Spectrometry
JF - Journal of the American Society for Mass Spectrometry
IS - 9
ER -