Mass Spectrometry & Purification Techniques
Open Access

The Use of Ionic Liquids in Mass Spectrometry and Their Limitations

John Ragab^{* *}Correspondence: John Ragab, Department of Chemistry, Cleveland State University, Cleveland, USA, Email:

Author info »

Description

Room-Temperature Ionic Liquids (RTIL) are molten salts with melting points less than 100 degrees Celsius. Because of their particular qualities, they have been employed in catalysis, separations, mass spectrometry, and other applications. They have been used as an ion coupling reagent for electrospray ionization mass spectrometry (ESI-MS), a solvent for liquid-liquid extraction, stationary phases for chromatography, and electrochemical solvents. Several features of the materials boosted and improved the analysis utilizing spectrometry.

In general, a mass spectrometer has five parts: a sample intake, an ion source, an analyzer, a sensor, and a vacuum. Ionic liquids' primary purposes in mass spectrometry are to increase analyte ionization, as a solvent, and as an ion-pairing reagent for ESI-MS. The article is an instructional piece for researchers interested in the use of ionic liquids in mass spectrometry.

The article mostly discusses Electrospray Ionization Mass Spectrometry (ESI-MS), Matrix Aided Laser Desorption/ Ionization Mass Spectrometry (MALDI-MS), and Desorption Corona Beam Ionization (DCBI) and Desorption Corona Beam Ionization Mass Spectrometry (DCBI-MS). Mass spectrometry is an analytical method that relies on the ionization of the subject under investigation. Ionization could occur via Electron Impact Mass Spectrometry (EIMS), Fast Atom Bombardment Mass Spectrometry (FAB-MS), Secondary Ion Mass Spectrometry (SIMS), Electrospray Ionization (ESI), Laser Desorption/ Ionization (LDI), Plasma Desorption (PD), and Matrix Assisted Laser Desorption/Ionization (MALDI) Hard ionization procedures, such as Electron Impact- Mass Spectrometry (EI-MS), gave important information for elucidating chemical structure. Soft ionization techniques, on the other hand, gave superior ionization for thermally labile materials such as protein, peptides, biomolecules, DNA, and so on (no fragmentations). Several aspects of laser desorption/ionization mass spectrometry, are promising. This approach may be used to analyse solid materials as well as surfaces. The latter use is critical for direct biochip analysis, thin film and Thin Liquid Chromatography (TLC).

The direct desorption/ionization utilizing the laser (Laser Desorption/Ionization Mass Spectrometry, LDI-MS) has numerous limitations; it is confined to analytes with high laser energy absorption. It also produced analyte fragmentation and used a lot of laser energy. As a result, a tiny organic molecule (matrix) was employed to absorb laser energy and aid in the desolvation process. The matrices allowed for proton transfer with the analyte under study. Thus, the general requirements for effective MALDI matrices are: 1) They must disintegrate and cocrystallize with the target, 2) They must have suitable chromophoric groups that strongly absorb the laser radiation, 3) They must be stable for storage, 4) They must be steady under high-vacuum circumstances, 5) They must inhibit both chemical and thermal deterioration of the analyte, and 6) They must help the sample's dielectric breakdown process. After ionization, the ions were isolated in petrol phase using m/z. As a result, the desorption/ionization process is affected by the laser wavelength. UV-MALDI (255 or 337 nm) is the most often used laser.

Most of these criteria do not apply to nanoparticle applications (Surface Assisted Laser Desorption/Ionization Mass Spectrometry (SALDI-MS). Because of the large number of undesired adducts, organic matrices frequently have low spectra quality. They generated inhomogeneous sample locations. In addition, certain of these matrices are unstable in water. Before laser shots, benzoic acid matrices were sublimed and removed from the sample. This disadvantage revealed variance in the sample analysis over time. Due of these disadvantages, a variety of ILs were used.