Advantages and disadvantages of different mass spectrometry analysis methods

Quadrupole mass spectrometer, QMS

QMS is the most common mass spectrometry instrument with outstanding quantitative ability, accounting for the vast majority in GC-MS.

Advantages:

Simple structure, low cost, and easy maintenance;

The quantitative ability of SIM function is strong, and it is an instrument and equipment used in most detection standards.

Disadvantages:

Lack of cross polarity ability and insufficient qualitative ability;

Low resolution (unit resolution), with interference from isotopes and other ions with m/z approximation;

Slow speed and low quality limit (less than 1200u).

Time of Flight Mass Spectrometer, TOFMS

TOFMS is the fastest mass spectrometer suitable for LC-MS applications.

Advantages:

It has good resolution, which is helpful for qualitative analysis of the difference between the m/z approximate ion and the ESI spray ion source;

Fast speed, with 2-100 high-resolution full scan (such as 50-2000u) spectra per second, suitable for fast LC systems (such as UPLC);

High quality limit (6000~10000u).

Disadvantages:

No string pole function, which limits further qualitative ability;

The selling price is higher than QMS;

More precise and requires careful maintenance.

Triple quadrupole mass spectrometer, QQ

QQ mass spectrometry provides a cascade function for quadrupole mass spectrometers while retaining the strong quantitative ability of QMS, enhancing the qualitative ability of mass spectrometry. It is often used as a confirmation detection method for QMS in detection standards.

Advantages:

Has string pole function and strong qualitative ability;

Very good quantitative ability, MRM has a higher signal-to-noise ratio than QMS's SIM;

It is a commonly used QMS result confirmation instrument;

In addition to the general sub ion scanning function, QQQ also has functions such as SRM, MRM, mother ion scanning, and Neutrality loss (ion trap not working);

Studying the structure of characteristic groups is of great help.

Disadvantages:

Insufficient resolution and susceptibility to ion interference from m/z approximation;

High selling price;

Careful maintenance is required.

Quadrupole ion trap, QTrap

Technically speaking, auxiliary RF has been added to the quadrupole of traditional QQ, which can be selectively excited; Or in terms of functionality, it provides QQ with multi-level cascade functionality.

Advantages:

Simultaneously equipped with MRM, SRM, neutral loss, and multi-level cascade functions, it is very suitable for structural analysis of unknown samples.

Disadvantages:

The resolution is still a bit low.

Ion trap mass spectrometer, ITMS

Ion trap mass spectrometer is the simplest tandem mass spectrometry commonly used for structural identification.

Advantages:

Cost lower than QQ, compact in size;

Having multi-level cascade capability, suitable for qualitative research in molecular structure, able to provide local structural information of molecules, better than QQ.