Continuous-flow extractive desorption electrospray ionization coupled to normal phase separations and for direct...

Area of Science:

• Analytical Chemistry
• Separation Science
• Mass Spectrometry

Background:

• Normal phase liquid chromatography (NPLC) is widely used for chiral separations, particularly for drug intermediates like chiral amines.
• Electrospray ionization mass spectrometry (ESI-MS) offers high sensitivity but faces challenges with organic eluents common in NPLC, leading to poor ionization efficiency.
• Existing interfaces struggle to efficiently couple NPLC with ESI-MS due to eluent composition.

Purpose of the Study:

• To develop and demonstrate a novel interface for coupling NPLC with ESI-MS.
• To overcome the ionization efficiency limitations of traditional ESI with organic NPLC eluents.
• To enable sensitive detection of chiral amines and phospholipids using NPLC-MS.

Main Methods:

• Implementation of continuous-flow extractive desorption electrospray ionization (CF-EDESI) by introducing NPLC eluents via a hypodermic needle into the electrospray plume.
• Analysis of aromatic amine-functionalized enantiomers using NPLC coupled with CF-EDESI-MS.
• Direct infusion of bacterial cell extracts for phospholipid monitoring using CF-EDESI-MS.

Main Results:

• CF-EDESI successfully interfaced NPLC with MS detection, overcoming poor ionization efficiency in organic solvents.
• The method demonstrated sensitivity comparable to or exceeding ultraviolet detection for chiral amine enantiomers.
• Sensitive detection of phospholipids in bacterial cell extracts was achieved, even from non-ESI-friendly solvents, with tunable ion forms.

Conclusions:

• Continuous-flow extractive desorption electrospray ionization is an effective technique for interfacing normal phase liquid chromatography with mass spectrometry.
• This approach significantly enhances sensitivity for analyzing challenging analytes like chiral amines and phospholipids.
• CF-EDESI offers a versatile solution for sensitive molecular analysis in complex biological samples.