Using Electrospray-Assisted Laser Desorption/Ionization Mass Spectrometry To Characterize Organic Compounds Separated on Thin-Layer Chromatography Plates

Abstract

Electrospray-assisted laser desorption/ionization (ELDI), an ionization method that combines laser desorption and electrospray ionization (ESI), can be used under ambient conditions to characterize organic compounds (including FD&C dyes, amines, extracts of a drug tablet) separated in the central track on a thin-layer chromatography (TLC) plate coated with either reversed-phase C18 particles or normal-phase silica gel. After drying, the TLC plate was placed on an acrylic sample holder set in front of the sampling skimmer of an ion trap mass analyzer. The chemicals at the center of the TLC plate were analyzed by pushing the sample holder into the path of a laser beam with a syringe pump. The molecules in the sample spot were desorbed by continuously irradiating the surface of the TLC plate with a pulsed nitrogen laser. Then, the desorbed sample molecules entered an ESI plume where they were ionized through the reactions with the charged species (including protons, hydronium ions and their cluster ions, solvent ions, and charged droplets) generated by electrospraying a methanol/water solution. MS/MS analyses were also performed to further characterize the analytes. The detection limit of TLC/ELDI/MS is approximately 10(-6) M. This was evaluated by using FD&C red dye as the standard. A linear relationship was found for the calibration curve with the concentration of FD&C red dye ranged from 10(-3) to 10(-6) M.

Established and emerging atmospheric pressure surface sampling/ionization techniques for mass spectrometry

“…The observation of the typical multiply charged envelope of ions from LD/ESI of proteins indicates that at least some of the laser-desorbed protein is dissolved in the charged electrospray droplets and proceeds to form ions by the typical ESI route. 73 Using this technique, it was possible to perform direct characterization of chemical compounds like amines on TLC plates 74 and detect intact proteins in dried biological fluids (e.g. blood, tears, saliva, and serum), bacterial cultures, and tissue 73 without a chemical matrix added to the samples to enhance the desorption process.…”

Analysis of Amphiphilic Lipids and Hydrophobic Proteins Using Nonresonant Femtosecond Laser Vaporization with Electrospray Post-Ionization

“…dissolved in blood. Such ion suppression effects are common when performing post-ionization using ESI and have been observed in literature [8,29,30]. Despite the ion suppression effects, DHPC can still be vaporized, ionized, and analyzed from the whole blood sample.…”

Ambient in situ analysis and imaging of both hydrophilic and hydrophobic thin layer chromatography plates by electrostatic spray ionization mass spectrometry

“…Interfacing TLC with ambient ionization MS without much sample pretreatment prior to MS analysis is more convenient in the view of fast analysis. Recently, several ambient ionization methods, including electrospray ionization (ESI) based techniques, [21][22][23][24][25][26][27] APCI, 28 DART…”