UV/VIS Spectroscopy Overview

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson
Download our mobile app to listen on the go
Get App

Questions and Answers

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.

False (B)

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.

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

Match the detector types with their features:

<p>Photomultiplier tubes = Measures light intensity Laser induced fluorescence = Uses lasers for detection Charge-coupled device (CCD) = Captures image and spectrum Mass spectrometer = Analyzes ions based on mass-to-charge ratio</p> Signup and view all the answers

Which light source is commonly used in Atomic Absorption Spectroscopy (AAS)?

<p>Hollow Cathode Lamp (C)</p> Signup and view all the answers

Flame Emission Spectroscopy (FES) is more sensitive than Atomic Absorption Spectroscopy (AAS).

<p>False (B)</p> Signup and view all the answers

What is the primary purpose of nebulization in sample introduction?

<p>To transform the liquid sample into a fine mist.</p> Signup and view all the answers

The ________ is responsible for providing the required heat to atomize the sample in AAS.

<p>Flame and Burner</p> Signup and view all the answers

What is a limitation of Atomic Absorption Spectroscopy (AAS)?

<p>It only provides quantitative analysis. (B)</p> Signup and view all the answers

Flame Nebulization involves mixing the sample mist with air and combusting it with _____ gas.

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

Match the detector types with their characteristics:

<p>Flame Spectroscopy = Simple and cost-effective for visible light Atomic Absorption Spectroscopy = Highly sensitive for trace amounts Graphite Furnace Atomization = Improved sensitivity for trace detection Flame Nebulization = Uses a burner and flame to atomize</p> Signup and view all the answers

Name one alternative to the Hollow Cathode Lamp for light sources.

<p>Electrodeless Discharge Lamps (EDL)</p> Signup and view all the answers

What is the primary purpose of a monochromator in analytical chemistry?

<p>To select a specific wavelength of light (D)</p> Signup and view all the answers

The presence of anions in a sample can lead to anionic interference that improves the detection of the analyte.

<p>False (B)</p> Signup and view all the answers

What type of detector is often used in analytical instruments due to its sensitivity in detecting low light intensities?

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

A ______ flame can achieve higher temperatures than an air/acetylene flame.

<p>nitrous oxide</p> Signup and view all the answers

Match the following types of interference with their causes:

<p>Ionization = High temperatures causing partial ionization Viscosity = High viscosity leading to incomplete atomization Anionic Interference = Presence of phosphate ions complexing with analyte Spectral Interference = Overlapping absorption or emission lines</p> Signup and view all the answers

What effect does ionization have on measurement sensitivity?

<p>Decreases sensitivity (B)</p> Signup and view all the answers

A detector measures light intensity after it has been directly sourced from the flame.

<p>True (A)</p> Signup and view all the answers

Name a treatment method used to correct for viscosity interference in samples.

<p>Advanced instruments like double-beam spectrometers or background correction methods.</p> Signup and view all the answers

Flashcards

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

The nebulizer turns liquid samples into a mist to enter the plasma.

ICP-OES Torch Function

The torch converts argon gas into a plasma using radio waves, to excite the sample's atoms.

ICP-OES Polychromator

The polychromator separates the light from the plasma into various wavelengths (colors of light).

Signup and view all the flashcards

ICP-OES High Sensitivity

ICP-OES can detect very low amounts of elements (ppm, ppb, ppt).

Signup and view all the flashcards

Atomic Absorption Spectroscopy (AAS)

A technique that measures the absorption of light by atoms in a sample, used for detecting trace elements.

Signup and view all the flashcards

Flame Emission Spectroscopy (FES)

A technique that measures the emission of light by atoms when heated, used for analyzing elements that emit visible light.

Signup and view all the flashcards

Hollow Cathode Lamp

A light source in AAS that emits specific wavelengths of light corresponding to the element being analyzed.

Signup and view all the flashcards

Nebulization

The process of transforming a liquid sample into a fine mist for introduction into a flame or furnace.

Signup and view all the flashcards

Graphite Furnace Atomization

A sample introduction method in AAS that uses a graphite tube to atomize the sample at high temperatures, increasing sensitivity.

Signup and view all the flashcards

Trace Element Detection

Identifying very small amounts of elements in a sample.

Signup and view all the flashcards

Quantitative Analysis

Measuring the amount of a substance in a sample.

Signup and view all the flashcards

Sample Matrix

The materials surrounding the element of interest in a sample that can interfere with analysis.

Signup and view all the flashcards

Flame Atomization

Uses a flame (usually air/acetylene) to heat a sample to its atomic state for analysis.

Signup and view all the flashcards

Monochromator Function

Isolates a specific wavelength of light (color).

Signup and view all the flashcards

Ionization Interference

High flame temperatures cause elements to become ions, reducing free atoms for accurate measurement.

Signup and view all the flashcards

Ionization Suppressors

Added to flames to prevent ionization errors and improve sensitivity.

Signup and view all the flashcards

Viscosity Interference

High sample viscosity in methods like graphite furnaces can cause incomplete atomization, leading to background interference.

Signup and view all the flashcards

Spectral Interference

Overlapping absorption/emission lines from sample components or instrument parts, creates wrong readings.

Signup and view all the flashcards

Anionic Interference

Anions in the sample can complex with the analyte, affecting accurate measurements.

Signup and view all the flashcards

Detector Function

Measures the intensity of light after it passes through the flame, indicating element concentration

Signup and view all the flashcards

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)

Studying That Suits You

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

Quiz Team

Related Documents

UV-Visible Spectroscopy PDF

More Like This

Mastering UV-VIS Spectroscopy
10 questions

Mastering UV-VIS Spectroscopy

EruditeStarlitSky avatar
EruditeStarlitSky
UV Spectroscopy Quiz
5 questions

UV Spectroscopy Quiz: Test Your Knowledge of UV-Vis Spectroscopy

ExcellentNovaculite4988 avatar
ExcellentNovaculite4988
Analytical Chemistry Chapter 2: Spectroscopy Overview
15 questions

Analytical Chemistry Chapter 2: Spectroscopy Overview

ProgressiveBasilisk avatar
ProgressiveBasilisk
UV/Vis Spectroscopy Overview
20 questions

UV/Vis Spectroscopy Overview

TrustworthyYellow5490 avatar
TrustworthyYellow5490
Use Quizgecko on...
Browser
Open
Browser
Browser