Membrane-Based Continuous Remover of Trifluoroacetic Acid in Mobile Phase for LC-ESI-MS Analysis of Small Molecules and Proteins

Abstract

We developed a "continuous" trifluoroacetic acid (TFA) remover based on electrodialysis with bipolar membrane for online coupling of liquid chromatography (LC) and electrospray ionization mass spectrometry (ESI-MS) using TFA containing mobile phase. With the TFA remover as an interface, the TFA anion in the mobile phase was removed based on electrodialysis mechanism, and meanwhile, the anion exchange membrane was self-regenerated by the hydroxide ions produced by the bipolar membrane. So the remover could continuously work without any additional regeneration process. The established LC-TFA remover-MS system has been successfully applied for the qualitative and quantitative analysis of small molecules as well as proteins.

Reversed-Phase Liquid Chromatography of Peptides for Bottom-Up Proteomics: A Tutorial

“…When liquid chromatography is online hyphenated to mass spectrometry, the advantages of using TFA for peptide separation quickly become significant disadvantages since the stable ion pairs and the increased surface tension of solutions with TFA prevent efficient ionization using electrospray. , Much effort has been spent on keeping TFA usable for LC-MS of peptides and proteins because of its superior chromatographic properties, particularly in RPLC of proteins, where it dramatically limits undesirable secondary interactions and maintain the compact structure of the analytes. − While the superior chromatographic performance of TFA, or recently its less fluorinated alternative difluoroacetic acid, added to the mobile phase at least in some percentage, may still predominate the signal suppression in protein LC-MS analyses, ,− modern stationary phases with reduced silanol activity and positive surface charge enable efficient separation of peptides only with formic acid.…”

Simultaneous Determination of 6 Antiallergic Components in Asarum sieboldii Using High-Performance Liquid Chromatography

“…Although the 3 types of acids did not differ significantly, we selected trifluoroacetic acid, which is a widely used mobile phase and is reported to have better resolution and peak shapes than other acids. [32][33][34] The most suitable conditions for quantitative analysis (detection wavelength of 290 nm) were obtained using a gradient elution of the mobile phase consisting of 0.1% (v/v) trifluoroacetic acid (A) and acetonitrile (B). The 6 compounds were separated within 30 minutes, and the retention times of echinacoside, vanillic acid, kakuol, methyl eugenol, sesamin, and asarinin were 8.2, 9.4, 19.7, 20.5, 21.4, and 22.6 minutes, respectively.…”

A stationary phase with a positively charged surface allows for minimizing formic acid concentration in the mobile phase, enhancing electrospray ionization in LC-MS proteomic experiments

“…6–9 Because of its appealing effects in the RPLC of peptides, various efforts have been undertaken to make TFA suitable for LC-MS proteomic analyses. 10–15…”