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Atomic Absorption Spectrophotometry: Principles and Techniques, Exams of Nursing

University of CambridgeNursing

A concise overview of atomic absorption spectrophotometry (aas), a reference method for trace metal analysis. It explains the principles of aas, including how atoms absorb specific wavelengths of light to move electrons to higher energy orbitals, and how the amount of light absorbed is directly proportional to the concentration of the analyte. Essential components such as hollow cathode lamps, atomization methods (flame and graphite furnace), and techniques to address interferences like matrix effects and background absorbance. It also touches on inductively coupled plasma atomic emission photometry (icp-aes) as a reverse process for measuring trace elements. This material is useful for students and professionals in analytical chemistry and related fields.

Typology: Exams

2024/2025

Available from 11/09/2025

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Atomic Absorption Spectrophotometry
Atomic Absorption Spectrophotometry - correct answer A
reference method for trace metals such as lead
Atoms absorb - correct answer lines (single λs) of light and in
so doing an electron is moved to a higher energy orbital
The energy of the light absorbed equals - correct answer the
energy difference between electron orbitals
Light absorbed is directly proportional to - correct answer
concentration
When the atoms return to the ground state - correct answer
they emit light of the same wavelength
AA - correct answer more sensitive than absorption
spectrophotometry because all of the light passing through the sample can be
absorbed by the atoms
The Hollow Cathode Lamp - correct answer The source lamp
must supply sufficient light of one of the lines used by the element. This requires a
hollow cathode lamp
What is the cathode made of? - correct answer the element to
be measured
What is the current used for? - correct answer used to ionize
the Noble fill gas in the lamp
pf3
pf4
pf5

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Atomic Absorption Spectrophotometry

Atomic Absorption Spectrophotometry - correct answer A reference method for trace metals such as lead Atoms absorb - correct answer lines (single λs) of light and in so doing an electron is moved to a higher energy orbital The energy of the light absorbed equals - correct answer the energy difference between electron orbitals Light absorbed is directly proportional to - correct answer concentration When the atoms return to the ground state - correct answer they emit light of the same wavelength AA - correct answer more sensitive than absorption spectrophotometry because all of the light passing through the sample can be absorbed by the atoms The Hollow Cathode Lamp - correct answer The source lamp must supply sufficient light of one of the lines used by the element. This requires a hollow cathode lamp What is the cathode made of? - correct answer the element to be measured What is the current used for? - correct answer used to ionize the Noble fill gas in the lamp

What happens when the cations collide with the cathode - correct answer cause the atoms of the cathode to sputter off into the fill gas. Colllisions with the fill gas ions excite the atoms causing an outer shell electron to jump into a higher energy orbital. The excited atoms emit the wavelength of interest when they return to the ground state What must be removed by the monochromator? - correct answer Fill gas light emissions What must the sample be? - correct answer atomized (i.e., ions converted to ground state atoms) Flame (acetylene/air or nitrous oxide) - correct answer • Is less sensitive because most of sample is lost

  • Requires precise control of aspiration and distribution of sample into the flame − Greatly influenced by sample viscosity Furnace made of graphite is heated electrically - correct answer •Higher order of sensitivity that is needed for lead •Sample diluted and transferred directly into a graphite tube •L'vov platform prevents sample from clinging to the sides •Slower measuring process than flame atomization Graphite furnaces heat the sample in 3 or more stages - correct answer 1.) 100oC to dry the sample 2.) 1000oC to char the sample to dry ash and vaporize proteins (Ar injected to vent and dissipate proteins) 3.) 2600o to atomize Unwanted Reactions Can Occur - correct answer Formation of oxides, hydroxides and thermostable salts can interfere with atomization

Interferences - correct answer Matrix, chemical, ionization, background absorbance Matrix - correct answer viscosity and proteins are major factors that cause measurement error if samples are compared to aqueous standards

  • Use protein based standards to mimic plasma protein-binding
  • Dilute standards and unknowns to minimize viscosity differences Chemical - correct answer thermostable bond forms with anions (e.g. Ca+2 and Mg+2 with PO -3)
  • Use a chelator, La2O3 to bind the phosphate thus displacing Ca+ Ionization - correct answer too much energy causes ejection of an outer shell electron
  • Add easily ionized salt such as NaCl to the diluent Background absorbance - correct answer molecules absorb some of source light
  • Measure molecular absorption with wide bandpass uv light
  • Zeeman correction Deuterium background correction - correct answer Uses wide bandpass to measure molecular absorption

Zeeman background correction - correct answer Splits the source into side bands with a magnet