1. Principles and Practices¶
a very brief and general introduction to mass spectrometers¶
Mass spectrometers come in various flavors. Layout of a typical mass spectrometer is shown in Figure 1.1 below. Its major components include:
a. a sample inlet: for introducing the sample into the mass spectrometer, can be direct injection, or eluate of a gas or liquid chromatograph;
b. an ion source: for generating gas-phase ions of analytes in the sample;
c. an m/z analyzer: for separating analyte ions (formed in the previous step) on the basis of their m/z values;
d. a detector: for generating a signal for the ions that hit it, and recording their m/z values and abundances (as intensities); and
e. a data acquisition and analysis system: for operating the mass spectrometer to acquire data; and for post-processing of raw data
Figure 1.1: Layout of a typical mass spectrometer showing its major components: a sample inlet; an ion source; an m/z analyzer; a detector; and a data acquisition and analysis system.¶
There are different options (or designs) available for all parts of a mass spectrometer, but not every design of each part is compatible with every design of the other parts, and so mass spectrometers of different configurations are available from various instrument manufacturers. When buying a mass spectrometer, the applications (or purposes) for which it is needed is a major criterion influencing the choice of configuration.
I would like to build a low cost chromatography/mass spectrometry system as proof of concept, and as an exercise to learn different skills that go into instrumentation building. Cost, both initial and operational, is a major criterion influencing buying decision when considering such instrumentation. A simple liquid chromatography-electrospray ionization-triple quadrupole mass spectrometer (LC-ESI-QqQ MS) can easily cost USD 150,000 - USD 200,000. For a lot of laboratories, and purposes, such initial costs can be prohibitively expensive, and so, I am particularly interested in building a low cost electrospray ionization-(single) quadrupole mass spectrometer (ESI-Q MS) (Figure 1.2).
