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Dushyant Patel LC-MS/MS Method

S.K.P.C.P.E.R., Kherva 18 M .Pharm. Thesis

CHAPTER: 4 DEVELOPMENT AND VALIDATION OF

LC-MS/MS METHOD FOR ESTIMATION OF GABAPENTIN

IN HUMAN PLASMA

4.1 INTRODUCTION TO LC-MS/MS:

4.1.1 MASS SPECTROMETRY (MS):

¾ Mass spectrometry (MS) has an important place amongst the various spectrometric

techniques for molecular analysis. The phenomenon of deflection of ions in electric or

magnetic field first was proposed by Wien in 1898. A mass spectrometer for general

use however available after 1930 only. At present it is most sensitive method of

molecular analysis. Moreover, it has the potential to yield information on the relative

molecular mass and the structure of the analyte. The principle of MS is production of

ions that are subsequently separated or filtered according to their mass-to-charge (m/z)

ratio and detected. The resulting mass spectrum is a plot of the (relative) abundance of

the generated ions as a function of m/z ratio

. Thus MS is a very sensitive, highly

selective and quantitative analytical technique. Sample size is usually in microgram to

the nanogram range and fragmentation patterns are highly reproducible even for multi-

component mixtures.

¾ The Mass spectrometer nowadays is a highly sophisticated and computerized

instrument

1-4

. It basically consists of five parts: sample introduction, ionization, mass

analysis, ion detection and data handling. Sample introduction systems comprise

controlled leaks, through which a sample vapor is introduced from a reservoir, various

direct insertion probes for the introduction of solids and low-volatility liquid and

combination with various chromatographic techniques. The ionization of the analytes

can be performed in a number of ways the available ionization techniques can be

classified in four groups, i.e. electron ionization, chemical ionization, desorption

ionization and nebulization ionization

1,5

. Proton transfer, charge exchange,

electrophilic addition and anion abstraction reaction used to produce positively

charged ions , M

or MH

. Negative ions are produce by proton transfer or

abstraction and anion attachment. After the production of ions, these are analyzed

according to their m/z ratio in time or space with the mass analyzer. This means that a

singly charged molecule with molecular mass of 400 will give a peak at m/z 400,

while a molecule carrying 40 charges and a molecular mass of 16,000 will also give a

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Samsung RT34M Manuale Utente Pagina 30