Atom spectrophotometry Flashcards
What is atomic spectrophotometry
it is the use of the absorption or emission of visible light to.
What is atomic absorption
It is when light is shone unto a metal and they take the amount / wave length of energy the require to vibrate.
Beer lambert law applies
More sensitive than atomic emission
what is atomic emission
It is when electrons are given light and when the release energy they give OUT the light
What are the uses of atomic emissions
Detection and quantification of alkali and some alkaline earth metals (group 1 and 2)
>K+, Na, calcium in dialysis
>Measuring calcium in vaccines (e.g. Diphtheria and tetanus).
> Measuring of sodium and potassium in urine.
Advantages of atomic emission spec
Robust, cheap and selective way to quantify some metals.
can be both quantitative and qualitative
How is the atomic emission measure (instrumentation)
> Sample is drawn into or placed in the flame.
Flame is generated by acetlene/compressed air (~2500oC).
Radiation emitted is filtered (to remove interference from flame or other components) or placed through a monochromator.
The intensity of emitted light is detected using a photosensitive cell.
What are the limitation of Atomic emission spect (AES)
Ionisation: At high temperatures atoms may completely lose an electron rather than it just get excited
> Reduces sensitivity
>Strotium chloride added
Viscosity: Rate of the liquid when drawn up is different based on viscosity
>Ethanol added to reduce viscosity to prevent false reading
>Sucrose can be added to make it more viscous
Anionic interference: sulphates and phosphate can cause formation of salts which are involatile
>Latium chloride added to precipitate the sulphur and phosphate
Why is strontium chloride added into the solution
This is because it is more easily ionised and so takes supresses ionisation of the sample.
What is standard addition and why is it used
The standards are in a different solution to the samples
Adding increasing volumes of standard solution to a fixed volume of sample to form a calibration series
What are the uses of atomic absorption spec
Detection and quantification of metallic elements in broader range than AES.
>Determining metal residues remaining from chemical manufacturing of drugs >tests such as zinc analysis in zinc insulin suspension;silver analysis in cisplatinum; and calcium, magnesium, mercury and zinc analysis in water used for diluting haemodialysis solutions
What are the strengths of AAS
More sensitive that AES. Highly specific
what is the instrumentation of AAS
> Similar to AES, but uses a hollow cathode lamp which emits light specific to metal under analysis.
Sample atomised by a flame or other method (e.g. graphite furnace).
Radiation from cathode lamp passes through atomised sample and a monochromator to a detector where absorption of the specific wavelength related to the metal is detected
What is inductively coupled plasma emission spectroscopy
emission spectroscopy that uses a very high temperature plasma (7000oC)
At such high temperatures all metals will emit radiation as they are excited and then return to ground state.
Sometimes ICP is coupled to MS, since part of the process creates ions which can be detected by MS.
What is lanthum chloride used for
Stop anionic interference (salt formation)
