unit 1 mass spectrometry Flashcards
what is a mass spectrometer?
a useful instrument used to determine the relative atomic masses
what are the different stages in mass spectrometry?
- ionisation
- acceleration
- ion drift
- detection
- data analysis
what are the 2 types of ionisation?
- electron impact
- electrospray
what happens during electrospray ionisation?
the sample is dissolved in a volatile solution and forced through a small nozzle/needle making a high pressure jet. the tip of the needle is connected to a positive terminal of a high voltage supply, causing each sample particle to gain a H+ ion
What happens during electron impact ionisation?
the sample is vaporized and an electron gun fires high energy electrons at the sample. This knocks one electron off each sample particle, so they become 1+ ions.
What happens in the ion drift chamber?
It will measure the time it takes to cover the fixed distance of the ions to the detector
What happens in the acceleration stage?
the ions are accelerated in an electric field so they all have the same kinetic energy, in which the positively charged ions will repel the positive plate, and will attract the negative plate, in which they will move towards the TOF chamber. The acceleration ensures that all ions enter the mass analyzer at the same speed.
How does the mass of the isotope relate to the velocity?
The isotopes with smaller mass number will have a high velocity than the heavier ones, meaning It would take less time to cover the fixed distance
What is the role of the detector?
when ions hit the detector, an electric current is generated. This current can be measured to determine the number of ions arriving at the detector. The more ions that hit the detector, the larger the current. The spectrometer registers the number of ions detected at each mass-to-charge ratio over a range (spectrum) of values.
How does the mass spectrometer use the data?
The mass spectrometer produces a mass spectrum that shows the relative abundances of the isotopes present, based on the data collected from the number of ions detected at different mass-to-charge ratios.
what is molecular mass spectrometry?
method used to analyze the masses of molecules by ionizing chemical compounds to generate charged molecules or fragments and measuring their mass-to-charge ratio (m/z).
what are the different peaks in the molecular mass graphs?
-Molecular Ion Peak (M⁺)
-Fragmentation Peaks
-Isotope Peaks
What does the Molecular Ion Peak (M⁺) represent in the molecular mass graph?
The peak with the highest m/z value typically represents the molecular ion, which is the molecule with one electron removed. This peak gives the molecular mass of the compound.
What does the fragmentation peak represent in the molecular mass graph?
Smaller peaks at lower m/z values represent fragments of the molecule. These occur when the molecular ion breaks apart and can provide information about the structure of the molecule.
