spectrometers Flashcards
(18 cards)
What is the Mass Spec
A mass spectrometer is a scientific instrument used to determine isotopic composition, separate isotopes of a given element and calculate the relative atomic mass
Vaporisation
Sample gets affected by heat and gets turned into gaseous form
Ionisation
Vaporised sample, gets bombarded with a high energy electron beam.
(Gaseous sample loses 1 or 2 electrons in their valence shells forming +1 and +2 ions.)
Accelaration
The current ions are accelerated by an electric field forming a high speed beam of positive ions
Deflection
Positive ions encounter a magnetic field, Individual ions are deflected in circular paths of radius based to their mass to charge ratio.
How does degree resemble the mass?
The heaver the isotope the larger the degree of mass
Detection
Detects the intensity and radius of deflection.
The detector count resembles the isotopic abundance
The degree of deflection resembles the mass of the isotope
AAS
A qualitative method used to determine the concentration of an element (mainly a metal or metalloid) in a mixture through absorption
Hollow cathode Lamp
A beam of light from the H.C.L (made from the same metal being analysed so that the metal can absorb the same wavelength of light being produced), is passed through the sample.
Atomiser
Atomiser turns ions into atoms in its flame, as the light from the HCL hits the metal being analysed it is known to be absorbed. The degree of light absorbance is proportional to the concentration of metal in the sample.
Monochromator
Selects a specific wavelength of light being absorbed.
Detector
Measure the intensity of light being produced and the degree that it has been absorbed.
Why does the mass spec only accept ions
As Ions can be passed around by magnetic and electric fields
Why does the AAS only accept metals
- Metals have a unique light absorption patterns
- Metals can form ions easily
Can the AAS analyse more than one metal at a time
No, as the wavelength of the metal being analysed have to match the wavelengths of the metal being absorbed.
Flame test
The flame test is a simple experiment used to identify unknown metal ions based on the colour they produce in a flame.
Flame test theory
- heat from the flame is supplied as energy towards the electrons, electrons absorb the energy making them become excited allowing them to jump to a higher energy level.
- As the electrons are at a higher energy level they are known to be very unstable.
- Electrons then fall back emitting energy in the form of photons.
- these photons have a specific wavelength that corresponds to a particular colour of light that is also known to be unique to each given element.
Calibration curve
Used to determine the unknown concentration of an element in a mixture/ solution.
a graph of concentration versus absorbance, plotted with specific points, drawn with the line of best fit, added to establish the relationship.
absorbance on the y axis and concentration on the x axis
