Elimination Technique for Alkali Metal Ion Adducts from an Electrospray Ionization Process Using an On-line Ion Suppressor

Abstract

Herein, a macrolide immunosuppressive drug, tacrolimus, was selected as a model compound that can easily form the sodium adduct ion derived from the ESI process in the positive-ion mode. 19,20 In this report, an on-line ISP technique is described as a simple and new way to eliminate alkali metal ion adducts derived from the positive-ion ESI process.

Observation of CO2 and solvent adduct ions during negative mode electrospray ionization Fourier transform ion cyclotron resonance mass spectrometric analysis of monohydric alcohols

“…Figure 3(a) shows that the O3 and O4 ions are present in the mass spectrum. However, compared to Figure 3(a) shows that when using methanol as a solvent, the difference in elemental composition between O3 and O4 class species was [CH 4 O], and Fig. 3(b) shows that when using ethanol as a solvent, the difference in composition between O3 and O4 species was [C 2 H 6 O].…”

“…Each of the model compounds, octadecanol, cholesterol or squalanol, was dissolved in methanol, ethanol or acetonitrile. The final solution was doped with 20 μL of 28% NH 4 OH to facilitate deprotonation of the alcohols to yield high amount of ions.…”

“…In addition to the deprotonated ions, O3 class species were present in all three FT-ICR mass spectra and O4 class species were only present in the spectrum of squalanol. The difference in elemental composition between O3 and O4 class species was [CH 4 O] and between O3 and O1 class species was [CO 2 ].…”

“…When the collision voltage was 15 V, the O4 adduct ions were not observed. When the collision voltage was 20 V, the peak of [M-CH 4 ]…”

“…[2,3] When the ESI is not well controlled, facile adduct formation can lead to a large variation in MS analysis results. [4] Athough the newly developed method can be used to characterize the super-complex saturated hydrocarbons in heavy oils, [1] we found that the monohydric alcohols could form O3 and O4 adduct ions in negative ion ESI FT-ICR MS (the 'O3' and 'O4' in this paper are referred to the ions containing 3 and 4 oxygen atoms in addition to carbon and hydrogen atoms). The formation of these adduct ions could led to incorrect interpretation of ESI mass spectra.…”