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In analytical chemistry a technique for determining the concentration of an element within a sample. |
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Atomic absorption spectroscopy in analytical chemistry is a technique for determining the concentration of an element within a sample. |
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Desolvation – the liquid solvent is evaporated, and the dry sample remains Vaporisation – the solid sample vaporises to a gas Volatilisation – the compounds making up the sample are destroyed, releasing free atoms. |
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#Desolvation – the liquid solvent? is evaporated?, and the dry sample remains #Vaporisation – the solid sample vaporises to a gas #Volatilisation – the compounds making up the sample are destroyed, releasing free atoms. |
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The flame is arranged such that it is laterally long (usually 10cm) and not deep. The height of the flame must also be controlled by controlling the flow of the fuel mixture. A beam of electromagnetic radiation is focussed through this flame at its longest axis (the lateral axis) onto a detector past the flame. |
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The flame is arranged such that it is laterally long (usually 10cm) and not deep. The height of the flame must also be controlled by controlling the flow of the fuel mixture. A beam of electromagnetic radiation is focussed through this flame at its longest axis (the lateral axis) onto a detector past the flame. |
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The frequency of the radiation in the beam is pre-set to a frequency that the element to be analysed is known to absorb at. The electrons of the atoms in the flame can be momentarily promoted to higher orbitals by absorbing a set quantity of energy (a quanta). This amount of energy is specific to a particular electron transition in a particular element. As the frequency of the radiation beam can be controlled, this amount of energy can be supplied in abundance. As the quantity of energy put into the flame is known, and the quantity remaining at the other side (at the detector) can be measured, it is possible to calculate how many of these transitions took place, and thus get a signal that is proportional to the concentration of the element being measured. |
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The frequency of the radiation in the beam is pre-set to a frequency that the element to be analysed is known to absorb at. The electrons of the atoms in the flame can be momentarily promoted to higher orbitals by absorbing a set quantity of energy (a quantum). This amount of energy is specific to a particular electron transition in a particular element. As the frequency of the radiation beam can be controlled, this amount of energy can be supplied in abundance. As the quantity of energy put into the flame is known, and the quantity remaining at the other side (at the detector) can be measured, it is possible to calculate how many of these transitions took place, and thus get a signal that is proportional to the concentration of the element being measured. |
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Interferences |
Interferences |
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Elements with very low ionisation? energies will cause interference by absorbing energy from the radiation beam that is not necessarily associated with the element that you are attempting to measure. Sodium is the most common cause of this interference. |
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Elements with very low ionisation? energies will cause interference by absorbing energy from the radiation beam that is not necessarily associated with the element that you are attempting to measure. Sodium is the most common cause of this interference. |
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Range of linearity |
Range of linearity |
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Fuel / oxidant mixtures |
Fuel / oxidant mixtures |
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:See also electromagnetic spectroscopy, spectroscopy, spontaneous emission |
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