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Dushyant Patel LC-MS/MS Method

S.K.P.C.P.E.R., Kherva 20 M .Pharm. Thesis

(A) For small volatile molecules

• Electron Ionization (EI).

• Chemical Ionization (CI).

(B) For small or non-volatile molecules

• Electrospray ionization (ESI).

• Matrix-assisted Laser Desorption Ionization (MALDI)

• Field desorption (FD).

• Fast Atom Bombardment (FAB).

Instrumentation:

Figure 4.1 Schematic diagram of Mass spectroscopy

¾ The mass spectrometer consists of an ionization source, ion guides, triple-stage mass

analyzer, and ion detection system. The ion guides, mass analyzer, ion detection system,

and part of the ionization source are enclosed in a vacuum manifold. Ionization of the

sample takes place in the ionization source. The specific process used to ionize the

sample is referred to as the ionization mode. The ions produced in the ionization source

are transmitted by the ion guides into the mass analyzer, where they are separated

according to their mass-to-charge ratio. The polarity of the potentials applied to the

lenses in the ionization source and ion guides determines whether positively charged ions

or negatively charged ions are transmitted to the mass analyzer. It can analyze positively

or negatively charged ions (called the positive or negative ion polarity mode).

¾ The ions produced in the ionization source are filtered according to their mass-to charge

ratios (mass analyzed) by the triple-stage mass analyzer, which can perform either one or

two stages of mass analysis. When the system is operated as a conventional mass

spectrometer with one stage of mass analysis, the sample is ionized in the ion source and

the ion products are subjected to mass analysis in the first rod assembly. The resulting

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