Question

Elaborate about the principle, advantages and where do we widely use of

1) MALDI-TOF/TOF

2) LC-MS/MS

Answer 1

MALDI /TOF ( Matrix-Assisted Laser Desorption Ionization Time-Of-Flight) mass spectrometry

In MALDI TOF system, the matrix is prepared by mixing or coating of sample with solution of an energy-absorbent, organic compound. On drying the matrix will crystallize. The sample will also entrap within the matrix by co-crystallization. Laser beams are used in this method. The sample within the matrix is ionized in an automated mode with a laser beam. Singly protonated ions from analytes are generates by desorption and ionization with the laser beam. The protonated ions are then accelerated at a fixed potential, where these separate from each other on the basis of their mass-to-charge ratio (m/z). The charged analytes are then detected using time of flight (TOF) analyzer. In this MALDI-TOF analysis, the m/z ratio of an ion is measured by determining the time required for it to travel the length of the flight tube. Ions with smaller m/z value (lighter ions) and more highly charged ions move faster.

The main advantage is to analyse the biomolecules such as DNA, Protein, peptides, sugars and also big organic molecules like polymers, dendrimers and macromolecules etc.

It is often utilized in tandem with other analysis and spectroscopy techniques in the diagnosis of diseases.

It is used in Biochemistry, Organic chemistry, Polymer chemistry, Microbiology, and Medicinal field.

LC/MS (Liquid Chromatographic Mass Spectroscopy)

Liquid chromatography (LC) separates the components of a sample based on differences in their affinity (or retention strength) for the stationary phase or mobile phase, then detects the separated components using UV, fluorescence, or electrical conductivity based on their properties. These separated compounds are sprayed on the mass spectrometry. In the mass spectrometry there is different type of ionization technique. Electron sprays ionization (EI), atmospheric pressure chemical ionization (APCI) etc. Here all the sprayed compounds are converted in to ions. The mass analyser will sort the ions based on the m/z ratio. The detector will count and give the signal generated from each ion.

LC/MS is using widely in analytical field.

It can analyse sample over a wide polarity range including ionic compounds.

It has no upper molecular weight limit. It can be used to analyse many thousands of Dalton.

It allows specific compound identification.

It is very sensitive as well as very selective.

It is used in Pharmacokinetic, Bioanalysis, Forensic science, Agrochemistry, Food analysis, Petrochemistry, Cosmetics etc.