chem Flashcards
mass spectrometry stages in depth
all air of spectrometer is pumped out, sample of element or compound is injected into mass spectrometer in gaseous form and is bombarded with high energy electrons from electron gun ,causing the atoms to loose electrons and form positive ions, the positive ions can fragment into 2 or more particles where one is positive the other neutral ,the positive ions have charge so are accelerated by an electrical field then deflected by the field ,ions with the same charge but greater mass deflect less than ions with lower mass .the ions of lower mass are detected first ,the magnetic field gradually increases and ions of greater mass are then detected ,the detector is connected to a computer that calculates the m/z ratio of each positive ion ,and its relative abundance compared with the most abundant particle .this can then be converted into a percentage for each positive ion.
what are the 4 main stages of mass spectrometry
ionisation,acceleration,deflection,detection
what ionisation technique is mostly used and how does it work
electron impact ionisation -electrons are bombarded at gaseous atoms from electron gun with enough energy to cause atoms to loose electrons to form positive ions.
what does the peak with the highest m/z ratio represent
the peak with the highest m/z ration represents the molecular ion (m+) which corresponds to the molecular mass of the molecule
how can you calculate the relative molecular mass of a molecule from its mass spectra
identify its molecular ion which corresponds to the molecular mass(if molecules charge is higher than one multiply molecular mass by this number to get the molecular mass of the molecule)
what causes fragmentation peaks in the mass spectrum?
fragmentation occurs when ions break down into smaller ions these fragments are detected and create peaks with lower m/z ratio corresponding to fragment masses
how do isotopes affect the appearance of the mass spectrum
lead to multiple peaks for an element
how can mass spectrometry be used in phramacuetical industry
can be used to identify impurities and determine the molecular structure of a substances during drug development.
why is it important to calibrate a mass spectrometer before used
ensure it provides right m/z values
what does the tallest peak in the spectrum represent
the ion with the most abundance
what is the role of the detector in mass spectrometry
detects the number of ions that hits it and produces a signal corresponding to the m/z ratio which is then generated to the mass spectrum
what do positive ions fragment
a smaller positive ion and a neutral fragment
what do fragmentation patterns show
they help to identify the structure of the molecule by providing information about which bonds break and which fragments are formed
What does isoelectronic mean
2 ions have the same amount of electrons
What is meant by molar volume of gas
How much space is occupied by one mole of gas
