Atomic Absorption Spectrometer Instrumentation - Part 1
21 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of the hollow cathode lamp in an atomic absorption spectrometer?

  • To atomize the analyte solution
  • To convert light signals to electrical signals
  • To emit resonance lines that match the absorption wavelengths of the analyte (correct)
  • To mix the flame gases with the analyte aerosol mist

    • Which component reduces the droplet size of the analyte solution in an atomic absorption spectrometer?

  • Signal processor
  • Mixing chamber
  • Nebulizer (correct)
  • Photomultiplier tube

    • What role does the monochromator play in the detection system of an atomic absorption spectrometer?

  • It converts light signals to readable formats
  • It emits high-temperature flames for atomization
  • It enhances the signal strength of the electrical signal
  • It selects resonance wavelengths for analysis while filtering out others (correct)

    • What is required to ensure that the analyte possesses a complete complement of valence electrons during atomization?

    <p>High temperature in the burner/flame</p> Signup and view all the answers

    Which component of the atomic absorption spectrometer is responsible for converting the light signal into an electrical signal?

    <p>Photomultiplier tube</p> Signup and view all the answers

    What is the role of Ar + ions in the sputtering process?

    <p>They strike the cathode to eject metal atoms.</p> Signup and view all the answers

    What happens to the excited gaseous metal after it emits photons?

    <p>It falls back to the ground valence energy level.</p> Signup and view all the answers

    What is contained in the equation Ca*(g) -----> Cao(g) + hc/λ?

    <p>It relates the energy emitted to the wavelength of the photon.</p> Signup and view all the answers

    What is the purpose of using a cup-shaped cathode in a hollow cathode lamp?

    <p>To ensure efficient redeposition of metal.</p> Signup and view all the answers

    In the reaction Ar +(g) + Cao(s) + e-s ----> Ar O(g) + Ca*(g), what is the result of the collision?

    <p>Production of excited gaseous ions.</p> Signup and view all the answers

    What is the primary emission wavelength for calcium?

    <p>422.7 nm</p> Signup and view all the answers

    What process occurs when gaseous metal redeposits onto the cathode?

    <p>Deposition</p> Signup and view all the answers

    What occurs during the energy transfer in sputtering?

    <p>Excitation of electrons in the cathode.</p> Signup and view all the answers

    What is the primary function of a Hollow Cathode Lamp (HCL)?

    <p>To emit narrow emission lines of analyte elements</p> Signup and view all the answers

    Which of the following components are part of the construction of a Hollow Cathode Lamp?

    <p>Pyrex body and cathode made of the element to be analyzed</p> Signup and view all the answers

    What type of lamp is generally more sensitive and accurate?

    <p>Single element lamp</p> Signup and view all the answers

    What occurs when an analyte in the flame absorbs part of the radiation produced by the HCL?

    <p>The intensity of radiation is reduced</p> Signup and view all the answers

    What gas is typically ionized in a Hollow Cathode Lamp to initiate the emission process?

    <p>Argon or Neon</p> Signup and view all the answers

    During the operation of the HCL, what happens to the electrons produced from the ionization process?

    <p>They are accelerated towards the anode</p> Signup and view all the answers

    Which symbol represents the intensity of radiation after it has passed through the sample in the HCL emission/absorption process?

    <p>P</p> Signup and view all the answers

    What does the HCL produce that results in a resonance absorption process in analytes?

    <p>Line spectrum with resonance wavelengths</p> Signup and view all the answers

    Study Notes

    Atomic Absorption Spectrometer Instrumentation - Part 1

    • The atomic absorption spectrometer uses a hollow cathode lamp (HCL) as the radiation source. This lamp emits specific wavelengths of light that match the absorption wavelengths of the analyte being measured.
    • The instrument utilizes a flame atomizer, including a nebulizer, mixing chamber, and burner/flame. The nebulizer reduces the analyte solution to an aerosol mist. Turbulent mixing occurs in the mixing chamber of the flame, followed by atomization and reduction within the burner or flame. The flame provides the high temperature necessary for atoms to be excited and absorb light.
    • The detection system in an AAS includes a monochromator
    • A monochromator selects the specific wavelength emitted by the HCL that corresponds to the analyte of interest.
    • The use of a photomultiplier tube (PMT) converts the light signal to an electrical signal.
    • A signal processor transforms the electrical signal into a readable format.

    Atomic Absorption Spectrometer Components

    • The hollow cathode lamp (HCL) emits wavelength(s) which match absorption wavelengths precisely of the atoms of interest.
    • The atomizer, with the nebulizer's function to reduce the analyte to a mist and the burner/flame for atomization.
    • The detection system has a monochromator which isolates the specific wavelength of light emitted by the analyte via its resonance. This wavelength is then filtered to isolate it. The PMT converts the light signal into an electrical signal and then the signal processor converts the electrical signal into a readable format.

    Double Beam AAS Design

    • The design of a double beam atomic absorption spectrometer uses a beam splitter to direct the light beam through both reference and sample beams.
    • This allows for automatic compensation of fluctuations in the light source intensity; it's a reference beam.

    AAS Components: Line Source

    • The hollow cathode lamp (HCL) is used to generate light matching the absorption wavelength of the analyte element.
    • The HCL consists of a sealed glass cylinder with a quartz window, a cup-shaped cathode made of the element to be analyzed, and an anode wire.
    • A neon or argon gas is typically used within the lamp at low pressure. Single-element lamps are more sensitive and accurate than multi-element lamps.

    Hollow Cathode Lamp (HCL)

    • The components of the HCL include a quartz window and a Pyrex body.
    • The inside components include an anode and cathode.

    HCL Emission - Analyte Absorption Process

    • The hollow cathode lamp (HCL) emits line spectra matching the analyte element.
    • The sample (gas) atoms within a flame absorb radiation from the HCL's line spectrum.
    • The absorption of this light reduces the intensity of the light emitted from the HCL

    HCL Emission/Absorption Process

    • The HCL produces a line spectrum with resonance wavelengths.
    • The analyte in the flame absorbs a portion of the emitted radiation.
    • The intensity of radiation decreases after passing through the sample and reaches the detector.

    Emission Spectra for HCL

    • Single-element lamps (example: Pd) have a single characteristic emission spectrum at their characteristic wavelengths.
    • Multi-element lamps (example: Cd, Pb, Cu) have multiple characteristic emission spectra, each for the specific element.

    Hollow Cathode Lamp Operation

    • Ionization of inert gas (Argon or Neon): High voltage ionizing the inert gas which produces positively charged inert gas ions and negatively charged electrons.
    • Sputtering process causes the atoms of the element to be excited and ejected from the cathode, creating an atomic vapour of the element, leading to an emission of resonance lines by excited electrons.
    • Emission of resonance lines: Excited electrons in the gaseous metal atoms fall to their ground valence energy level and emit discrete wavelength photons matching their specific wavelengths. 
    • Redeposition of cathode metal: Gaseous metal atoms redeposit onto the cup-shaped cathode.

    HCL: Cup Shaped Cathode

    • The cup-shaped cathode design improves efficiency of metal deposition, preventing it from depositing onto the cooler glass walls around it (improving HCL function).
    • The cup shape concentrates the light emitted, making the radiation more focused.

    Next Up: In Depth Look at the Atomizer

    • The figure shows a double beam design including a beam splitter.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Unit 3.2 - AAS Instrumentation Part 1 PDF

    Description

    This quiz covers the basic principles and components of atomic absorption spectrometers, focusing on the role of the hollow cathode lamp, flame atomizer, and detection systems like monochromators and photomultiplier tubes. Understanding these components is essential for anyone studying analytical chemistry and instrumentation technology.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser