Difference Between LC, LC-MS, LC-MS-MS, and HR-MS

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What is LC?

Liquid chromatography (LC) is 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 is Mass Spectrometry (MS) and LC-MS

Mass spectrometry is advanced substantial analytical technique becomes converted into ions in vacuum space to its mass to charge ratio (m/z) and quantify the magnitude of each ion and it produce mass spectra. This mass spectra gives vital details about molecular mass, structure, identity and quantity of sample which include qualitative and quantitative information. When the component exists in complex form then only MS is not do the separation because of identical molecular weight and fragmented pattern. Hence, MS with HPLC as a separation process is most suitable combination.

Moreover, in 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 LC detector. Hence, 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., Pharmaceutical, 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 HPLC instrument. In LC-MS-MS ions are isolated in first MS enters in collision cell and fragmented, this results into formation of ions called product ions which are separated in the second mass analyser and detected.

This instrument is very useful for complex sample matrix, very low amount of component 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 of 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?

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 by normal MS it is undistinguishable.

Earlier in large number conventional quadrupole and ion trap mass spectrometers 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:

  1. Time-of-flight MS (TOFMS),
  2. Orbitrap MS, and
  3. 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 produce 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 to the sequence of amino acids.

References

  1. De Hoffmann, J. Charette and V.Stoobant. “Mass Spectrometry, Principal & Applications,” John Wiley & Sons,
  2. 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,
  3. Ghaste, 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,
  4. Kumar, P. R., & Rini, R. (2016). LCMS-A REVIEW AND A RECENT UPDATE.
  5. Parasuraman, S., Anish, R., Balamurugan, S., Muralidharan, S., Kumar, K. J., & Vijayan, V. (2014). An Overview of Liquid Chromatography-Mass Spectroscopy Instrumentation. Pharmaceutical Methods.

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