AA Review

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Author:
saitclt
ID:
186965
Filename:
AA Review
Updated:
2012-12-05 13:49:03
Tags:
INST390 SAIT CLT2
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Description:
Cynthia's review of Atomic Absorption Terms and major concepts
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  1. AA requires the analytes to be a ___ state
    free atomic
  2. Each element absorbs in only one particular wavelength (True/False)
    False.  One particular element has many different possible electronic transitions and therefore many specific wavelengths it absorbs
  3. The ___ electrons undergo transitions when an atom absorbs light in AA
    outer shell
  4. What type of peaks result from atomic absorption?
    Very well defined, sharp peaks
  5. An atomic absorption spectrum is also referred to as a
    line spectrum
  6. A molecular absorption spectrum is also referred to as 
    • A continuous, or band spectrum
    • It is a broad peak
  7. Two types of line broadening
    • Doppler broadening
    • pressure broadening
  8. This type of broadening can be minimized by adjusting the flow rate
    Doppler broadening
  9. This type of broadening is worse at higher temperatures
    Pressure broadening
  10. If you're getting unwanted molecular spectral lines, what can you do? What species are likely causing them?
    • Change wwavelength 
    • Use a higher temperature fflame
    • Caused by OH-, CN-, other radicals 
  11. The line spectrum from the HCL is ____ than the atomic vapor spectra
    Sharper, since the HCL is at a lower temperature and pressure than the flame
  12. What element can't be used in a HCL?
    Mercury ( it would pour out)
  13. EDL
    Electrodeless discharge lamp
  14. An EDL uses the __ of a metal, which is ionized when an ___ is excited by ____
    • Salt
    • inert gas
    • RF field
  15. A ___ has a higher light intensity (10-100x) but is less stable than ___
    • EDL
    • HCL
  16. A chopper splits the light, which corrects for
    • Electronic noise
    • variations in lamp intensity
  17. The process by which a sample is vaporized and decomposed to its atoms
    Atomization
  18. The formation of a fine suspension of liquid droplets
    Nebulization
  19. Only about ___ of the sample actually reaches the flame
    5% or less
  20. Name three types of flameless AA
    • Graphite ffurnace
    • Hydride generation
    • Cold vapor
  21. Name two types of burners
    • Total consumption burner
    • laminar flow premix burner (what we've used)
  22. Which type of flame tends to be noisier?
    Nitrous oxide
  23. Name three zones of the flame, which one is usually used for the AA light beam?
    • Primary combustion zone
    • interconal region, most common, hottest area
    • outer cone
  24. Burner height has an affect on
    Absorbance
  25. As temperature increases, the number of atoms in ground state...
    Decreases
  26. As wavelength increases, atoms in ground state...
    Decrease
  27. Two ways to control flame temperature
    • Adjust air flow or fuel flow
    • switch fuel type or air type
  28. GFAA
    Graphite furnace atomic absorbance
  29. Two ways in which matrix modifiers work
    • Cause the interferences to vaporize before the analyte
    • Keep the interferences tied up so that the analyte vaporizes first
  30. Why can't you simple heat up your sample in the graphite furnace as fast as possible?
    The sample will splatter, making threport ductilereport ductile
  31. Graphite furnace is a good technique for which elements?
    Metalloids (almost metals) such as As, Se, Te, also lead
  32. HGAAS
    Hydride generation atomic absorption spectrometry
  33. Order the following from lowest to highest detection limit: ICP, Hydride Generation, Flame AA, Graphite Furnace
    • Hydride Generation (0.2 ppb)
    • Graphite Furnace (1 ppb)
    • ICP (40 ppb)
    • Flame AA (100 ppb)
  34. Does HGAAS use a nebulizer?
    No
  35. Does the oxidation state of the metalloid matter for hydride generation?
    Yes, it is crucial
  36. What is dangerous about the waste from HGAAS?
    It is strongy acidic
  37. What moves the generated hydride gas into the optical cell?
    An inert purge gas pushes it through
  38. Is time from chemical reaction to the optical cell important in HGAAS?
    Yes, shorter time is best and it must be consistent
  39. Cold Vapor AA is useful for what element?
    Mercury (Hg)
  40. Why can mercury be analyzed with Cold Vapor AA?
    It has a high vapor pressure
  41. What are some advantages of Cold Vapor AA?
    • Fewer matrix interferences
    • Fewer spectral interferences
    • Improved detection limits
  42. What chemical reactions must occur to prepare the mercury for analysis by Cold Vapor AA?
    • Oxidation (releases Hg from its compounds)
    • Reduction (converts all Hg ions to elemental Hg)
  43. Why is a scrubber needed after Cold Vapor AA analysis?
    Because the mercury vapors are toxic
  44. What are 2 disadvantages of Cold Vapor AA?
    • Intensive sample prep
    • Hg contamination in the lab
  45. If another element in your sample absorbs at the same wavelength as your analyte, what could you do?
    • Choose a different wavelength
    • Do sample prep before analysis to separate the interfering species
  46. Which emits a broader band - deuterium lamp or the HCL?
    Deuterium (its a molecule)
  47. Name 2 limitations of deuterium correction
    • Udercorrection or overcorrection can occur
    • The HCL and D2 lamp must be aligned perfectly
  48. The term for the splitting of electronic energy levels using a magnetic field so that several absorption lines are formed for each electronic transition.
    Zeeman Effect
  49. The Zeeman effect is mainly used for what AA technique?
    Graphite Furnace
  50. Name two types of chemical interferences
    • Formation of unwanted compounds
    • Ionization
  51. Two ways to deal with interferences caused by unwanted molecules forming with your analyte
    • Releasing Agent - add something which reacts with the interferant more than your analyte does, thus freeing up the analyte
    • Protective (Masking) Agent - Forms a complex with the analyte preventing anything else from getting to it
  52. Which type of flame is ionization more of a problem with?
    Nitrous
  53. What can you do if you're experiencing ionization interferences?
    Add an ionization suppressor such as K
  54. EIE
    Easily Ionizable Element
  55. What element may cause ionization problems (by being greedy for electrons)?
    Aluminum
  56. Mercury typically has a ___ hold time than other elements.  Why?
    • Shorter (Hg has a 26 day hold time instead of 6 months)
    • It's more volatile

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