Analytical Techniques Flashcards
what happens to the molecules in the sample during mass spectrometry
The molecules in the small sample are bombarded with high energy electrons which can cause the molecule to lose an electron
This results in the formation of a positively charged molecular ion with one unpaired electron
One of the electrons in the pair has been removed by the beam of electrons
what type of fragment ions will be detected first
The smaller and more positively charged fragment ions will be detected first as they will get deflected the most and are more attracted to the negative pole of the magnet
what does the base peak correspond to
the most abundant ion
what does each fragment correspond to
a specific peak with a particular m/z value in the mass spectrum
what are isotopes
different atoms of the same element that contain the same number of protons and electrons but a different number of neutrons.
what is relative abundance of an isotope
proportion of one particular isotope in a mixture of isotopes found in nature
what can mass spectroscopy be used to find
the relative abundance of the isotopes experimentally
what does small m/z value correspond to
either small or have a high positive charge or a combination of both.
what is infrared spectroscopy
a technique used to identify compounds based on changes in vibrations of atoms when they absorb IR of certain frequencies
what does a spectrophotometer do
irradiates the sample with electromagnetic waves in the infrared region and then detects the intensity of the wavelength of IR radiation which goes through the sample
how do atoms vibrate when energies of radiation are absorbed
bonds between atoms will vibrate by stretching, bending and twisting
at what specific frequency to molecules vibrate at to stimulate larger vibration
The resonance frequency
explain time of flight mass spectrometry
I
A
I
D
ionisation: sample of an element is vaporised and injected into mass spectrometer where high voltage is passed over and electrons removed leaving +1 ions
acceleration: positively charged ions accelerated towards negatively charged detection plate
ion drift : ions are deflected by magnetic field into curved path which is dependant on mass and charge
detection: positive ions hit negative charged detection plate where they gain an electron producing flow of charge
what does a greater current during the detection phase produce
a greater abundance of that particular ion
how can you deduce the formula of the fragment from m/z
m/z is equal to molecular mass
