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31 Cards in this Set
- Front
- Back
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What is a flame photometer?
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an instrument that burns sample and measures the light emission intensity at a given wavelength.
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What occurs in flame photometry?
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analytes are excited by flame, then the emit light while returning to ground state.
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what are the 5 components of a flame photometer?
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1. Flame
2. Atomizer 3. Monochromator 4. Detector 5. Readout |
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What is the Flame used for?
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1. As the sample holder
2. As the light source- emission is proptnl to analyte concent. |
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What are 3 requirements of the flame?
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1. Constant/proper temp
2. Can't interfere w/ emission spectra. 3. Must be steady, within location by the detector. |
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Where on the flame is emission monitored?
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at the middle of the flame where the temp is hottest.
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What is used for the flame?
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Propane and air at 1900 deg C
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What is the atomizer for?
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making fine mist droplets of the sample, and introducing it into the flame.
This decreases cooling of flame |
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what are 2 types of atomizers?
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1. Total consumption burner
2. Premixing burner |
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What "effect" is used by both types, and what does it do?
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Venturi effect - it pulls the sample up into the flame by negative force.
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What is the diffnc between a total consumption and a premixed burner?
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The premixed has sample entering flame in a fine mist, heavy materials go to waste chamber.
-Total consumpt introduces sample directly into flame via a CAPILLARY TUBE - not really an atomizer is it. |
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why is a monochromator used in flame photom?
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to eliminate spectral interference.
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what are 2 types of monochrom. used?
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1. Spectrophotometric isolation - it's uncommon.
2. Common: Filter w/ relativ. good bpss, but not highgrade. |
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What types of detectors can be used in flame photometers?
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1. Phototube
2. PMT |
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what is used for the readout?
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LED digital display
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what 2 types of instrument setups could be used?
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1. Single beam
2. Double beam in space |
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Why use a double beam?
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because single beam will give an unstable readout due to variation in the falme.
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what else must be used in flame photometry if it uses a double beam in space setup?
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AN INTERNAL STANDARD!
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what is an internal standard?
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1. Chemical added to unknown solution in known conc, and analyzed AT SAME TIME as unkn.
2. Unknown signal compared to the known signal. 3. Random flame fluctuations affect both to same degree, so gives a STABLE readout. |
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What are the criteria for the internal standard?
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-Must know the concentration
-Pure -Must have similar chemical/ physical properties as unknown -Must have excitation potentl similar to unknown -Must be on the same order of magnitude in concentration. -Emission spectra can't overlap w/ patient - shouldn'tbe in a patient normally. |
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What substances are used as internal standards?
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-Lithium
-Cesium |
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What are the advantages of the flame photometer's internal standard?
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-Eliminates flame temp fluctuat.
-Eliminates aspiration/atomizer errors. -Eliminates photodiode fluctuations when voltage changes. |
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What two problems are associated with flame photometers?
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1. Molecular interference
2. Operational error |
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How many kinds of molecular interferences can occur?
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5 - they are:
1. Background 2. Spectral 3. Chemical 4. Ionization 5. Self absorption |
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What is background?
How does it affect results? How is it corrected? |
the contribution of flame and sample diluent to emission signal. Increases the measrmnt.
to correct, zero the instrument with only diluent and internal standard. |
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what is spectral interference?
How does it affect results? How is it corrected? |
when 2 or more analytes have adjacent/overlapping emission spectra. Results are increased. To correct, use relatively narrow bpass filters.
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What is chemical interference?
How does it affect results? How is it corrected? |
ions combining with test analyte to form salts/acids/solids that change emission intensity.
Results are decreased; to correct take out the ree atoms. |
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What is ionization?
How does it affect results? How is it corrected? |
the excitation of an atom resulting in LOSS of electrons -can't give a signal then.
Decreases results; to correct, reduce the flame temp or make calibrators similar to biological sample. |
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What is self absorption?
How does it affect results? How is it corrected? |
the absorptoin of emitted light by another analyte inst. of detector. Decreases results; to correct dilute to an optimal concentration.
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what are 2 operational problems that can occur?
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1. Run out of gas - to correct, change the tank dummy.
2. Irregular aspiration rate due to clogs in probe - to correct remove the clog einstein. |
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What are 2 clinical applications of flame photometry?
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1. Serum-urine electrolyte panels for sodium and potassium
2. Lithium for therapeutic drug monitoring. |
