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16 Cards in this Set
- Front
- Back
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What type of radiation is used in AAS (Atomic Absorption Spectroscopy) ?
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Visible Light
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List the 5 components of an AAS?
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1. Light Source (hollow cathode lamp)
2. Atomiser 3. Monochromator 4. Detector 5. Read Out |
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What are the reasons for using AAS?
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To detect metals and metalloids.
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What is the basis of analysis of AAS?
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Electrons become excited when light is absorbed.
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List the chemical principles of AAS?
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AAS uses the absorption of light to measure the concentration of metal ions. The technique is based on the interaction of vaporised atoms with visible light from a cathode lamp. Atoms of a particular element when energised in a flame will absorb light from an emission lamp containing that same element. Electrons are promoted from low to high energy levels when light energy is absorbed. Different substances have different energy levels and the energy and wavelength of light required to promote electrons varies. |
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List the applications of AAS?
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- To detect the presence of metal ions
- Used to monitor the concentrations of micro-nutrients in soils - Used to detect excess or deficiency of metals in blood or urine samples. |
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State one advantage and one disadvantage of AAS?
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Advantage: The technique is rapid, allowing large numbers of samples to be measured in a short period of time.
Disadvantage: Only one element at a time –need a specific cathode lamp for specificmetal |
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What type of radiation is used for UV-Visible Spectroscopy?
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UV-Visible Light
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List the 5 components of the UV-Visible Spectroscopy?
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1. Light source
2. The Monochromator/Slit 3. Sample solution 4. Light detector 5. Recorder |
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List the 5 steps involved in the operations of AAS?
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1. Solutions of known concentrations are analysed first, then the solution to be tested follows.
2. The lamp emits light of certain wavelength required to excite electrons. 3. The solution of sample is then sprayed into the flame. 4. Monochromator selects light of a particular wavelength. 5. The amount of light absorbed by the flame is measured --> determination of the concentration of the analyte. |
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What are the reasons for using UV-Vis?
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UV-Vis measures the absorption of light at a particular frequency. Different substances can be analysed: eg: proteins, metal ions, inorganic compounds as long as they can absorb light in the UV-vis range. |
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What is the basis of analysis of UV-Vis?
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UV-Vis radiation excites bonding electrons which then emit light |
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What are the chemical principles of UV-Vis?
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UV-visible spectroscopy looks at the interaction of molecules or ions with visible and ultraviolet light.
Many substances absorb light of characteristic wavelengths. Light of a specific frequency or wavelength (nm) is used. When light passes through a compound, electrons absorb light energy which causes them to jump from lower energy levels to higher energy levels. The frequency/wavelength at which this happens can be used to distinguish between substances. |
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List the applications of UV-Vis?
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- Clinical analysis, measuring the concentration of organic compounds or coloured metal ions in blood or urine – Hb or sugar in blood.
- Determining amount of coloured dye in plastics, paints or household products. - Analysis of DNA and proteins. - Levels of glucose in a sample of urine. Measurement of the maximum absorbance at a specific wavelength. Creates a unique fingerprint spectrum. |
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List one advantage and one disadvantage of using UV-Vis.
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Advantage: Useful for a wide variety of chemicals. e.g. proteins, metal ions, inorganic compounds
Disadvantage: Only suitable for low molecular mass substances. |
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What are the 5 steps involved in the operation of UV-Vis?
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1. A light source produces radiation of all wavelengths and is shone through a slit to create a very narrow beam of light.
2. The light is then shone through a monochromator, which selects a specific wavelength of light to be passed through the sample. 3. The specific wavelength of light passes through the sample solution, which excites the electrons to higher energy levels. 4. The detector then measures the amount of light passed through the sample. 5. The results are then recorded and displayed. |
