Desorption/ionization efficiencies of triacylglycerols and phospholipids via EASI‐MS

Abstract

Knowledge of the major effects governing desorption/ionization efficiency is required for the development and application of ambient mass spectrometry. Although all triacylglycerols (TAG) have the same favorable protonation and cationization sites, their desorption/ionization efficiencies can vary dramatically during easy ambient sonic-spray ionization because of structural differences in the carbon chain. To quantify this somewhat surprising and drastic effect, we have performed a systematic investigation of desorption/ionization efficiencies as a function of unsaturation and length for TAG as well as for diacylglycerols, monoacylglycerols and several phospholipids (PL). Affinities for Na(+) as a function of unsaturation level have also been assayed via comprehensive metadynamics calculations to understand the influence of this phenomenon on the ionization efficiency. The results suggest that dipole-dipole interactions within a carbon chain tuned by unsaturation sites govern ionization efficiency of TAG and PL.

Observation of electrochemically generated nitrenium ions by desorption electrospray ionization mass spectrometry

“…The spray droplets hit the surface of the thin film of electrolyte solution, now thinner than 1 mm due to the N 2 nebulizing gas pressure, on the surface of the working electrode. Much like in DESI-MS and easy ambient supersonic spray 28–30 MS, tinier secondary microdroplets are directed into the mass spectrometer 31,32 and are analyzed with an LTQ Orbitrap XL hybrid mass spectrometer (Thermo Fisher Scientific, San Jose, CA) where the m / z ratio is determined utilizing the high mass accuracy and high resolving power of the Orbitrap mass analyzer. 33 …”

Detection of the Short‐Lived Radical Cation Intermediate in the Electrooxidation of N,N‐Dimethylaniline by Mass Spectrometry

“…The spray droplets hit the surface of the thin film of electrolyte solution, now thinner than 1 mm owing to the N 2 nebulizing gas pressure, on the surface of the working electrode. Much like in desorption electrospray ionization DESI‐MS15, 16 and easy ambient supersonic spray MS17–19, tinier secondary microdroplets are directed into the mass spectrometer20, 21 and are analyzed with an LTQ Orbitrap XL hybrid mass spectrometer (Thermo Fisher Scientific, San Jose, CA), where the m / z ratio is determined by utilizing the high mass accuracy and high resolving power of the Orbitrap mass analyzer 22…”

Detection of the Short‐Lived Radical Cation Intermediate in the Electrooxidation of N,N‐Dimethylaniline by Mass Spectrometry

“…500 nm radius) and is collected on aP ts ubstrate (5 mmr adius) separated from the Pt tip by af ew hundred nanometers.B yv arying the separation, the dimerization process was shown to follow second-order kinetics with arate constant of 2.5 10 8 m À1 s À1 .S ECM experiments could be performed at DMA concentrations as high as 0.4 mm in acetonitrile,u nder which conditions the half-life is 10 ms. At greater concentrations,the dimerization is reported to be too fast to obtain good collection efficiency. Thes pray droplets hit the surface of the thin film of electrolyte solution, now thinner than 1mmo wing to the N 2 nebulizing gas pressure,o nt he surface of the working electrode.M uch like in desorption electrospray ionization DESI-MS [15,16] and easy ambient supersonic spray MS [17][18][19] ,t inier secondary microdroplets are directed into the mass spectrometer [20,21] and are analyzed with an LTQOrbitrap XL hybrid mass spectrometer (Thermo Fisher Scientific,San Jose,CA), where the m/z ratio is determined by utilizing the high mass accuracya nd high resolving power of the Orbitrap mass analyzer. [1] This study suggests that many other short-lived electrochemical intermediates could be identified and studied by this means since MS is ageneral detector with high chemical specificity,unlike electrochemical detectors.…”

“…Thes pray droplets hit the surface of the thin film of electrolyte solution, now thinner than 1mmo wing to the N 2 nebulizing gas pressure,o nt he surface of the working electrode.M uch like in desorption electrospray ionization DESI-MS [15,16] and easy ambient supersonic spray MS [17][18][19] ,t inier secondary microdroplets are directed into the mass spectrometer [20,21] and are analyzed with an LTQOrbitrap XL hybrid mass spectrometer (Thermo Fisher Scientific,San Jose,CA), where the m/z ratio is determined by utilizing the high mass accuracya nd high resolving power of the Orbitrap mass analyzer. Thes pray droplets hit the surface of the thin film of electrolyte solution, now thinner than 1mmo wing to the N 2 nebulizing gas pressure,o nt he surface of the working electrode.M uch like in desorption electrospray ionization DESI-MS [15,16] and easy ambient supersonic spray MS [17][18][19] ,t inier secondary microdroplets are directed into the mass spectrometer [20,21] and are analyzed with an LTQOrbitrap XL hybrid mass spectrometer (Thermo Fisher Scientific,San Jose,CA), where the m/z ratio is determined by utilizing the high mass accuracya nd high resolving power of the Orbitrap mass analyzer.…”

“…electrode and the counter electrode is on the order of kiloohms.Above the rotating waterwheel system, ac ustom spray probe directs astream of sample microdroplets to the surface of the working electrode.N oh igh voltage is applied to the sample spray to minimize in-source oxidation. Thes pray droplets hit the surface of the thin film of electrolyte solution, now thinner than 1mmo wing to the N 2 nebulizing gas pressure,o nt he surface of the working electrode.M uch like in desorption electrospray ionization DESI-MS [15,16] and easy ambient supersonic spray MS [17][18][19] ,t inier secondary microdroplets are directed into the mass spectrometer [20,21] and are analyzed with an LTQOrbitrap XL hybrid mass spectrometer (Thermo Fisher Scientific,San Jose,CA), where the m/z ratio is determined by utilizing the high mass accuracya nd high resolving power of the Orbitrap mass analyzer. [22] DMA is proposed to electrochemically dimerize (Scheme 1) through electrooxidation to first form DMAC + .Tw oD MAC + units react to form the dimer, N,N,N',N'tetramethylbenzidine (TMB).…”