Mass Spectroscopy Flashcards
What is the definition of mass spec?
a technique used to measure the relative mass of molecules which requires the generation of analyte ions followed by ion detection and mass analysis
What are the major areas of application of Mass Spectrometry?
verification of drug identity, confirming presence of particular drug in formulated products, verifying presence of drug in clinical samples, identifying unknown drug metabolites, quality control of recombinant proteins, helps in sequencing of proteins, peptides etc and used in drug discovery
What are the principles and processes involved in MS?
molecules of sample ionized then identified according to mass, mass spectrum is a plot of intensity against mass to charge ratio, mass spectrometer is a device for producing and weighing ions
What are the key stages in performing experiments?
sample vaporization, ion generation, ion separation according to m/z ratios and ion detection
How can sample volatilization/ vaporization be achieved?
heat, placing sample in a vacuum or using fast atom bombardment
What are some ionisation techniques?
electron impact ionisation, matrix assisted laser desorption ionisation, atmospheric pressure chemical ionisation, fast atom bombardment, electroscopy ionisation and chemical ionisation
What are the components of a mass spectrometer?
vacuum chamber, ionisation chamber, magnetic sector, detector
Describe the method of electron impact ionisation
sample is vapourised by heat, ionisation achieved by bombarding volatilized molecules with electron beam, positive fragments produced are accelerated under vacuum through a magnetic field into deflection chamber
Describe the method of chemical ionisation
a stream of electrons used to ionize a reagent gas (ammonia or methane), results in production of strong acid , results in generation of protonated ions
What are some adv and disadv of EI and CI?
cheap and easy but produce a lot of fragments
Describe the process of fast atom bombardment
an analyte sample suspended in a viscous matrix is bombarded with a beam of fast moving Xe atoms , energy transfer from Xe atoms to matrix, break IM bonds and ionisation, desorption of analyte ions into the gas phase
What is the importance of the matrix in fast atom bombardment?
helps protect analyte from fragmentation, without it direct bombardment would lead to extensive fragmentation
1Describe the process of electrospray ionisation
soft ionisation technique which proceeds via protonation or deprotonation mechanism, analyte dissolved in mixture of org solvents, pH modifier used to produce ion
What is atmospheric pressure chemical ionisation?
similar to ESI but the gas phase ionisation is more effective than ESI for analyzing less polar species
What are the differences between matrix assistant laser desorption and fast atom bombardment?
the energy beam is transferred to matrix from a laser beam and the matrix must have a chromophore absorbing energy at wavelength of laser
