30 Questions
What is the primary purpose of radio-frequency spectroscopy of nuclei in a magnetic field?
To visualize the internal soft tissue of the body
What type of spectroscopy was used to discover the three-degree blackbody radiation?
Microwave spectroscopy
Which of the following is a characteristic of potentiometry?
Measuring electric potential while maintaining a constant current
Which of the following is a characteristic of amperometry?
Monitoring electric current while keeping the potential constant
What is the primary purpose of electroanalytical methods?
To apply an electrical signal to an electrode while measuring a different electrical property
What is the primary purpose of conductometry?
To measure conductance (the ability of a solution to carry an electric current) while a constant alternating-current (AC) potential is maintained between the electrodes
What is the first step in the process of chemical analysis?
Define the problem
What is the purpose of method modeling and plan in chemical analysis?
To develop a model representing the complex steps of the analytical method
What step is typically the most time-consuming in the implementation of an analytical method?
Sample preparation
What is the purpose of performing replicate measurements in chemical analysis?
To establish the precision of the method
What step involves comparing the analyte's signal to standards of known concentration and a calibration blank solution?
Compare results with standards
What information must be presented in every analytical result?
The precision of the analytical method
What is the purpose of an atomizer in atomic absorption spectroscopy?
To break analytes into free atoms
Which type of lamp emits many narrow emission lines in atomic absorption spectroscopy?
Hollow cathode lamp
What is the purpose of a monochromator in atomic absorption spectroscopy?
To isolate a single resonance emission line
In Flame Atomic Absorption Spectroscopy (FAAS), where does atomization of the sample occur?
In the presence of a gaseous mixture of an oxidant and a fuel
What is the function of the graphite tube in Graphite Furnace Atomic Absorption Spectroscopy (GFAAS)?
To atomize the sample as its temperature rises
What does the detector do in Graphite Furnace Atomic Absorption Spectroscopy?
Determines the absorbed fraction of the analytes
What is the main purpose of the quadrupole mass analyzer described in the text?
To allow only ions with a specific m/z or range of m/z to transmit through
What is the advantage of using a quadrupole as the first part of a tandem mass spectrometer?
It can act as a mass selector
What is the purpose of using selected reaction monitoring (SRM) in a tandem mass spectrometer with a quadrupole?
To quantitate analytes by selecting a precursor ion and its fragment ion
How is an ion trap mass spectrometer different from a quadrupole mass spectrometer?
It can store and manipulate ions
What is the advantage of an ion trap mass spectrometer over a quadrupole for full scan mode?
It is more sensitive
What is the purpose of the second analyzer in a tandem mass spectrometer with a quadrupole?
To act as a collision cell, allowing all the products to be transmitted to a third analyzer
What technique was popular in the 80's to early 90's for ionizing non-volatile compounds?
Fast Atom Bombardment (FAB)
What were the two most common matrices used in FAB?
Glycerol and 3-nitrobenzoic acid
What types of adducts could form with the analyte ions in FAB?
Protons, sodium ions, potassium ions, or ammonium ions
What technique involved replacing the atom beam in FAB with a beam of ions, typically cesium ions?
Secondary Ion Mass Spectrometry (SIMS)
What is the principle behind Electrospray Ionization (ESI)?
Creating a spray of charged droplets by applying a high voltage to a liquid flow
What process occurs in ESI to eject the ions from the charged droplets?
The ions are ejected by a combination of heat, vacuum, and acceleration into gas by voltages
Study Notes
Methods of Chemical Analysis
- The objective of chemical analysis is to provide information to solve a problem or make a decision, whether using classical (wet chemical) or instrumental methods.
Steps of Chemical Analysis
- Define the problem, requiring understanding of analytical techniques, problem-solving skills, experience, and intuition.
- Model the method, including a specific statement of the problem, information about the sample and analyte.
- Obtain and store the sample.
- Prepare the sample, which usually requires the largest investment of time.
- Perform measurements, including replicates to establish precision.
- Compare results with standards, involving a proper comparison of the analyte's signal to that of appropriate standards.
- Refine data and perform statistical treatment, presenting the precision of the analytical method.
Radiation Sources
- Deuterium lamps (DL) and electrodeless discharge lamps (EDL) are popular radiation sources.
Atomizers
- Atomizers break analytes into free atoms to analyze elements for their atomic constituents.
- Flame atomizers and graphite tube atomizers are commonly used in atomic absorption spectroscopy.
- Flame Atomic Absorption Spectroscopy (FAAS) involves nebulizing a solution of the sample into a flame.
- Graphite Furnace Atomic Absorption Spectroscopy (GFAAS) involves atomization in an open-ended graphite tube.
Monochromators
- A monochromator isolates a single resonance emission line from the hollow cathode lamp's many narrow emission lines.
- It collects light with many wavelengths and selects a narrow wavelength band.
Quadrupole Mass Analyzer
- A quadrupole mass analyzer uses a combination of radio-frequency (RF) and direct current (DC) voltages to select ions with a specific m/z or range of m/z.
- It is a low-resolution analyzer, often used in GC-MS and LC-MS applications.
- Quadrupole mass analyzers can be used in tandem mass spectrometry with selected reaction monitoring (SRM).
Ion Trap Mass Spectrometer
- Ion trap mass spectrometers are a type of three-dimensional quadrupole that can store and manipulate ions.
- They are more sensitive than simple quadrupole mass analyzers and can acquire tandem mass spectra.
Electroanalytical Methods
- Electroanalytical methods measure electrical signals or properties of a solution.
- Techniques include potentiometry (measuring electric potential), amperometry (measuring electric current), and conductometry (measuring conductance).
Fast Atom Bombardment (FAB) and Secondary Ion Mass Spectrometry (SIMS)
- FAB involves bombarding a sample with a beam of atoms, typically Ar or Xe, to ionize non-volatile compounds.
- The sample is mixed with a matrix, such as glycerol or 3-Nitrobenzoic acid, which allows the sample to refresh itself.
- SIMS replaces the atom beam with a beam of ions, typically cesium ions.
Electrospray Ionization (ESI)
- ESI creates an electrospray by applying a high voltage to a flow of liquid at atmospheric pressure, sometimes assisted by a concurrent flow of gas.
- The created spray is directed into the vacuum system of the mass spectrometer, where the droplets are de-solvated and ions are ejected and accelerated into the mass analyzer.
Learn about the steps involved in chemical analysis, from defining the problem to method modeling and planning. Understand the objectives behind performing chemical analysis using classical or instrumental methods.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
