What is LC?
Liquid chromatography (LC) is a fast and effective separation technique for the constituent of a mixture and purification of compounds. It is based on differential migration of the various components of a mixture through a stationary phase under the effect of a mobile phase.
What are Mass Spectrometry (MS) and LC-MS?
Mass spectrometry is an advanced substantial analytical technique that becomes converted into ions in vacuum space to its mass to charge ratio (m/z) and quantifies the magnitude of each ion and produces mass spectra. These mass spectra give vital details about molecular mass, structure, identity, and quantity of sample which include qualitative and quantitative information. When the component exists in the complex form then only MS is not doing the separation because of identical molecular weight and fragmented pattern. Hence, MS with HPLC as a separation process is the most suitable combination.
Moreover, in a combination of liquid chromatography with mass spectrometry, mass spectra molecular mass and structural information and LC provides qualitative information about retention time and quantifying analyte or constituent by using an LC detector. Hence, a combination of LCMS provides exceptional separation resolution of LC with the outstanding qualitative measurements of MS. LC-MS is used in various applications, e.g., pharmaceuticals, biochemicals, food, water, soil, forensic, environmental, petrochemicals, cosmetics, industrial, clinical research, and atomic physics.
What is LC-MS-MS?
LC-MS-MS instrument is the two mass spectrometry detectors connected to the HPLC instrument. In LC-MS-MS ions are isolated in the first MS enter in collision cell and are fragmented, this results in the formation of ions called product ions which are separated in the second mass analyzer and detected.
This instrument is very useful for complex sample matrices, a very low amount of components,s, and when the resolution is inadequate for both chromatography and its mass-to-charge ratio. Therefore, this technique provides a higher selectivity, specificity, and sensitivity which provides supplementary unique data on the mass and structure of the selected required component. It is very much useful in new chemical entity development, identification, and quantitation study of metabolites, polysaccharides, and proteins.
What is HR-MS?
In high-resolution mass spectrometry (HRMS) the mass can be measured to many decimal places. Normal MS is supposed to measure nominal mass and HRMS can measure exact mass so precisely that it can detect the minute differences in mass between two complexes whereas normal MS is indistinguishable.
Earlier a large number of conventional quadrupole and ion trap mass spectrometers were used. Now instruments such as Fourier-transform ion cyclotron resonance (FTICR) and modern orbitrap and Q-TOF systems are used. There are three types of HRMS:
- Time-of-flight MS (TOFMS),
- Orbitrap MS, and
- Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry.
Overall HRMS, the mass accuracy is below 5 ppm. The mass resolution specifies a capability to discriminate peaks, and a more resolution produces more separation. Considering the qualitative analysis TOFMS is exceptional on the basis of mass accuracy and more resolution.
This is a very significant technique for determining the structure of molecules and for finding the peptide mass data that states the sequence of amino acids.
References
- De Hoffmann, J. Charette and V.Stoobant. “Mass Spectrometry, Principal & Applications,” John Wiley & Sons,
- Breitkopf, SC, et al. “A relative quantitative positive/negative ion switching method for untargeted lipidomics via high-resolution LC-MS/MS from any biological source,” Metabolomics,
- Taste, M, et al. “Applications of Fourier transform ion cyclotron resonance (FT-ICR) and Orbitrap-based high-resolution mass spectrometry in metabolomics and lipidomics,” Int. J. Mol. Science,
- Kumar, P. R., & Rini, R. (2016). LCMS-A REVIEW AND A RECENT UPDATE.
- Parasuraman, S., Anish, R., Balamurugan, S., Muralidharan, S., Kumar, K. J., & Vijayan, V. (2014). An Overview of Liquid Chromatography-Mass Spectroscopy Instrumentation. Pharmaceutical Methods.
