why cant we use ionic liquid in LCMS because first the liquid passed through the LC column which have similar principle of HPLC and then only we are passing the sample in MS part.
We know that ionic liquids at times comprise of complex cations with alkyl group attached to it of variable length and nations. The separation of components in the sample takes place by virtue of interactions between analyte - stationary phase followed by analyte - mobile phase (ionic liquid) and the complex nature of the later description or partition of the analyte May be getting difficult. MS comes in the later stage after separation and quantification for identification of analyte. A suitable column in HPLC is required for the purpose. The viscosity of ionic liquid liquid is also a determining factor in the separation process.
Well one reason I can think of is the ionic liquid is made up of ions and therefore would show up in the mass spec in great excess compared to everything else.
"When a mass spectrometer is used as the LC detector (LC-MS), the mobile phase must be volatile, because one of the functions of the LC-MS interface is to vaporize the mobile phase. This means that the most popular buffer for LC-UV work, phosphate, cannot be used. Ammonium acetate is sufficiently volatile for LC-MS use, but we are left with the 2.0
The problem lies in the low volatility of the ILs. Unless they are covalently bound to the column resin, they will sooner or later eluate and end up in the MS, which because of their non volatility is problematic. There are a few ILs, that under high vacuum and high temperature might be volatile enough, but those usually are split into their comprising starting materials in the gas phase and then recombine on cooling to form the IL again.
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