Podcast
Questions and Answers
Which component of an ICP-OES system disperses emitted radiation into different directions?
Which component of an ICP-OES system disperses emitted radiation into different directions?
- Torch
- Polychromator (correct)
- Nebulizer
- Detector
A monochromator is capable of analyzing multiple wavelengths simultaneously.
A monochromator is capable of analyzing multiple wavelengths simultaneously.
False (B)
What gas is used to create the plasma in an ICP-OES?
What gas is used to create the plasma in an ICP-OES?
Argon
The _____ is responsible for introducing a liquid sample into the ICP-OES system.
The _____ is responsible for introducing a liquid sample into the ICP-OES system.
Match the detector types with their features:
Match the detector types with their features:
Which light source is commonly used in Atomic Absorption Spectroscopy (AAS)?
Which light source is commonly used in Atomic Absorption Spectroscopy (AAS)?
Flame Emission Spectroscopy (FES) is more sensitive than Atomic Absorption Spectroscopy (AAS).
Flame Emission Spectroscopy (FES) is more sensitive than Atomic Absorption Spectroscopy (AAS).
What is the primary purpose of nebulization in sample introduction?
What is the primary purpose of nebulization in sample introduction?
The ________ is responsible for providing the required heat to atomize the sample in AAS.
The ________ is responsible for providing the required heat to atomize the sample in AAS.
What is a limitation of Atomic Absorption Spectroscopy (AAS)?
What is a limitation of Atomic Absorption Spectroscopy (AAS)?
Flame Nebulization involves mixing the sample mist with air and combusting it with _____ gas.
Flame Nebulization involves mixing the sample mist with air and combusting it with _____ gas.
Match the detector types with their characteristics:
Match the detector types with their characteristics:
Name one alternative to the Hollow Cathode Lamp for light sources.
Name one alternative to the Hollow Cathode Lamp for light sources.
What is the primary purpose of a monochromator in analytical chemistry?
What is the primary purpose of a monochromator in analytical chemistry?
The presence of anions in a sample can lead to anionic interference that improves the detection of the analyte.
The presence of anions in a sample can lead to anionic interference that improves the detection of the analyte.
What type of detector is often used in analytical instruments due to its sensitivity in detecting low light intensities?
What type of detector is often used in analytical instruments due to its sensitivity in detecting low light intensities?
A ______ flame can achieve higher temperatures than an air/acetylene flame.
A ______ flame can achieve higher temperatures than an air/acetylene flame.
Match the following types of interference with their causes:
Match the following types of interference with their causes:
What effect does ionization have on measurement sensitivity?
What effect does ionization have on measurement sensitivity?
A detector measures light intensity after it has been directly sourced from the flame.
A detector measures light intensity after it has been directly sourced from the flame.
Name a treatment method used to correct for viscosity interference in samples.
Name a treatment method used to correct for viscosity interference in samples.
Flashcards
ICP-OES Principle
ICP-OES Principle
ICP-OES uses an argon plasma to excite atoms. Excited atoms emit specific wavelengths (light) which identify the elements. The light intensity relates to the element's concentration.
ICP-OES Nebulizer
ICP-OES Nebulizer
The nebulizer turns liquid samples into a mist to enter the plasma.
ICP-OES Torch Function
ICP-OES Torch Function
The torch converts argon gas into a plasma using radio waves, to excite the sample's atoms.
ICP-OES Polychromator
ICP-OES Polychromator
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ICP-OES High Sensitivity
ICP-OES High Sensitivity
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Atomic Absorption Spectroscopy (AAS)
Atomic Absorption Spectroscopy (AAS)
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Flame Emission Spectroscopy (FES)
Flame Emission Spectroscopy (FES)
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Hollow Cathode Lamp
Hollow Cathode Lamp
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Nebulization
Nebulization
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Graphite Furnace Atomization
Graphite Furnace Atomization
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Trace Element Detection
Trace Element Detection
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Quantitative Analysis
Quantitative Analysis
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Sample Matrix
Sample Matrix
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Flame Atomization
Flame Atomization
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Monochromator Function
Monochromator Function
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Ionization Interference
Ionization Interference
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Ionization Suppressors
Ionization Suppressors
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Viscosity Interference
Viscosity Interference
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Spectral Interference
Spectral Interference
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Anionic Interference
Anionic Interference
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Detector Function
Detector Function
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Study Notes
Electromagnetic Radiation (EMR)
- EMR is radiant energy released through electromagnetic processes
- Covers a range of frequencies called the electromagnetic spectrum
- UV/VIS spectroscopy uses specific parts of the spectrum (UV: 200-400nm; Visible: 400-700nm) to analyze matter
Spectroscopy vs. Spectrometry
- Spectroscopy studies the interaction between matter and radiated energy
- Spectrometry is the quantitative measurement of the spectrum (light intensity vs. wavelength)
- Spectrophotometry measures how much light is reflected or transmitted by a sample at different wavelengths
Principle of UV/VIS Spectroscopy
- UV/VIS spectroscopy measures the absorbance of ultraviolet (UV, 185-400 nm) and visible (VIS, 400-700 nm) light by a sample
- Light passing through the sample is partly absorbed; remaining light is transmitted
- Each compound absorbs light at a specific wavelength (the analytical wavelength), revealing its concentration and composition
- Absorption is due to electron excitation in chromophores (molecular regions) from a lower to a higher energy state
- Absorbance (A) follows the Beer-Lambert law: absorbance is proportional to the concentration of absorbing species in the sample
How UV/VIS Spectroscopy Works
- Radiation passes through a solution; bonding electrons become excited
- Excited electrons occupy a higher quantum state, absorbing some energy from the radiation
- The lower the electron's energy in the bonds, the longer the wavelength of absorbed energy
- Transmitted light is measured; unabsorbed light passes through the sample solution
Interactions of UV/VIS Radiation with Chromophores
- Chromophores are functional groups within molecules responsible for light absorption
- These groups have specific energy gaps between orbitals that align with visible light
- Alternating double bonds affect color by absorbing specific wavelengths and transmitting others
- Isolated chromophores absorb at specific wavelengths
- Conjugated chromophores absorb at longer wavelengths (bathochromic shift) and are more intense (hyperchromic effect)
- Examples of chromophores include the amine group (-NH2) and the nitro group (-NO2)
General Applications of UV/VIS Spectroscopy
- Quantitative Analysis: Determines compound concentration using Beer-Lambert law
- Qualitative Analysis: Identifies compounds based on their absorption spectrum
- Monitoring Reactions: Tracks changes in absorbance over time to study reaction kinetics
- Purity Testing: Detects impurities in pharmaceuticals, chemicals, and biological samples
Strengths and Limitations of UV/VIS Spectroscopy
- Strengths*
- Non-destructive and simple to use
- Quick, providing fast results
- Can be used for qualitative and quantitative analysis
- Inexpensive compared to other advanced techniques (NMR, MS)
- Limitations*
- Limited structural information (can only determine chromophore presence)
- Spectral overlap in mixtures can complicate analysis
- Requires samples to have chromophores for light absorption
Instrumentation Components
- Light Source (UV/VIS): Deuterium (UV) or Tungsten (Visible) lamp
- Monochromator: Disperses light into its component wavelengths
- Slits: Control beam width - narrow for higher resolution but reduced light intensity)
- Optics: Lenses/mirrors (often achromatic) to focus light onto/from the sample
- Sample Cells: Quartz (UV) or glass (visible) - cuvettes for samples
- Detector: Photomultiplier tubes (PMTs), or photodiode arrays (PDAs) to convert light into an electrical signal (higher sensitivity preferred)
Light Intensity and Beer-Lambert Law
- Transmission (T): Ratio of transmitted light intensity to incident light intensity
- Absorbance (A): Logarithmic measure of light absorbed by the sample (A = -logT)
- Beer-Lambert Law: Relates absorbance to concentration and path length (A = εcl, where ε = molar absorptivity, c = concentration, l = path length)
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