Question

What is selected reaction monitoring? Why is it also called MS/MS? Why does it improve the signal-to-noise ratio for a particular analyte?

Short answer

The process of selected ion montoring is also called mass spectrometry / mass spectrometry (MS/MS) or tandem mass spectrometry because the process inciuded mass filtration in two of its quadrupoles.

Step-by-step solution

 Selected reaction monitoring

Selected reaction monitoring happens after ion pass through the skimmer, right before it reaches the detector. This type of monitoring is divided into three parts, each quadrupole having a different function.

 Answering the above mentioned question

Selected reaction monitoring happens after ion pass through the skimmer, right before it reaches the detector.

This type of monitoring is divided into three parts, each quadrupole having a different function.

The first quadrupole, functions as a filter for the ions from the skimmer. It only lets precursor ions with a certain m/z into the second quadrupole.

The second quadrupole is called collision cell the precursor inos are bombarded by N₂ or Ar at 10^-3to 10^-1 Pa. This bombarded causes the precursor ions to break into fragment a phenomenon that can be called “collisionally activated dissocitation “

The fragment of the precursor ions now called product ions, are then filtered by the third quadrupole before it reaches the detector. This quadrupole could filter out certain range of m/z, or allow passage for ions with certain m/z.

Because of the increase in selectivity for the analyte of interest, the single-to-nolse ratio is improved.

The process of selected ion montoring is also called mass spectrometry / mass spectrometry (MS/MS) or tandem mass spectrometry because the process inciuded mass filtration in two of its quadrupoles .