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AAS Flash
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- 1What is ion separation?It is the process of separating ions based on their m/z ratio.
This is done by applying an electric or magnetic field to an ionised sample. - 2What are mass resolution and high mass resolution?Mass resolution describes the ability of a mass spectrometer to distinguish between ions of similar m/z ratios.
High mass resolution allows for more accurate identification and quantification of individual ions in a complex mixture. - 3What is a quadrupole mass analyser?It is a type of mass spectrometer that uses an oscillating electric field to separate ions based on their m/z ratio.
Four parallel rods are arranged in a square pattern. Ions enter the quadrupole and are subjected to RF (radio frequency) and DF applied to the rods. The RF voltage causes the rod to oscillate.
Only ions with a specific m/z ratio will have a stable trajectory through the quadrupole and others will be ejected. By adjusting the RF voltage applied to the rods, different m/z ranges can be selected and transmitted to the detector. - 4What is a magnetic sector?It is a type of mass analyser used to separate ions based on their m/z ratio.
It contains a curved magnetic field causing ions to flow in a curved path. As ions pass through the magnetic field, they experience a Lorentz force.
This force causes ions with different m/z ratios to follow different paths through the magnetic field and exit the sector at different positions.
By adjusting the strength of the magnetic field and the size of the sector, different m/z ranges can be selected and transmitted to the detector. - 5What are the advantages of a quadrupole over a magnetic sector?- Low cost and simplicity
- Higher scan speed
- Flexibility
- Tandem mass spectrometry - 6What is FTMS (Fourier Transform Mass Spectrometry?It is a type of mass spectrometry that uses Fourier transform techniques to obtain high mass resolution.
Ions are trapped in a magnetic field like an ion cyclotron resonance cell where they oscillate at different frequencies based on their m/z ratios.
RF is applied to the cell to the maintain oscillation of the ions. - 7What are the advantages of FTMS?- High mass resolution and accuracy
- High sensitivity
- Can obtain structural info on molecules
- Can measure the relative abundance of isotopes in a sample.
- High dynamic range which means it can detect and measure ions over different concentrations.
- Can be used with a variety of ionisation sources. - 8What is Tandem mass spectrometry (MS/MS)?It is a technique that involves two or more stages of mass spectrometry to provide additional information on the structure and composition of molecules.
A specific ion is selected and then fragmented by collision-induced dissociation (CID).
Then the fragmented pattern is analysed to provide info on the molecular structure and composition of the ion. - 9What is GC-MS?It's an analytical technique that separates, identifies and quantifies volatile and semi-volatile compounds in complex mixtures.
- 10What is LC-MS?It's an analytical technique that separates, identifies and quantifies NON-volatile complex mixtures.
- 11What are the sources of ionisation in LC-MS and GC-MS?GC-MS - Electron impact
LC-MS - Electrospray (ESI) - 12What are the basic components of a Mass Spectrometer?- Ion source - where the sample is ionised.
- Mass analyser - where the ions are separated based on their m/z ratio.
- Detector - where the separated ions are detected and converted into an electrical signal.
- Data system - where the electrical signal is processed and converted into a spectrum. - 13What is an Isotope?Atoms of the same element with the same number of protons but a different number of neutrons.
Same chemical properties but different atomic mass.
e.g. Carbon-12, 13, 14. - 14What is an Isobar?Atoms of different elements that have the same atomic mass but different atomic numbers.
Different numbers of protons and electrons but the same neutrons.
e.g. carbon-14, nitrogen-14. - 15What is an Isotone?Atoms of different elements that have the same number of neutrons but different numbers of protons and electrons.
Different atomic masses and numbers but the same neutrons.
e.g. carbon-14, nitrogen-15. - 16What is nuclear stability?The ability of the atomic nucleus to remain intact without undergoing decay or breaking apart into fragments.
- 17What factors affect nuclear stability?- Number of protons and neutrons in the nucleus.
- Nuclear binding energy
- Strength of the nuclear force that holds nucleus together - 18What are alpha and beta decay?Two types of radioactive decay
Alpha decay - Atomic nucleus emits an alpha particle with two protons and neutrons. The process reduces the atomic number by two and the atomic mass by four.
Beta decay - Atomic nucleus emits an beta particle which can be a beta - or a beta +.
Beta decay occurs when there is instability in the ratio of neutrons to protons.
In beta -, a neutron is converted into a proton.
In beta +, a proton is converted into a neutron. - 19what is Gas ionisation?When a crystal emits light when it is exposed to ionising radiation like gamma rays or X-rays.
- 20What is a scintillation detector?It consists of a scintillating crystal like sodium iodide, coupled with a photodetector.
When radiation enters the crystal, it interacts with the atoms in the crystal and produces scintillation light which is then detected by the photodetector. - 21What are liquid scintillation detectors?They are types of scintillation detectors that use a liquid scintillator instead of a crystal e.g. benzene.
The liquid scintillator is contained in a glass vial along with the sample. The ionising radiation interacts with the sample in the liquid scintillator and produces scintillation light which is then detected by the light detector. - 22What are the analytical uses of radionuclides? (4 Uses)- Chemical pathway studies - Using a radioactive tracer to study the pathway of chemical reactions to find out the final product.
- Radioisotope dilution method - Adding a known quantity of a radioactive isotope to a sample and then measure the concentration of the isotope in the mixture.
- Environmental monitoring - Can be used to monitor pollution.
- Radioimmunoassay (RIA) - Measures the concentration of specific molecules like hormones. - 23What are the advantages and disadvantages of applications like drugs, steroids, and polypeptide hormones?Adv
- Sensitivity
-Specificity
- Simplicity
Disadv
- Difficulty in producing binding agent
- Cross-reactions with molecules
- Limited precision. - 24How is DSC carried out? (Differential Scanning Calorimetry)- Sample holder contains the drug sample.
- Reference holder contains a sample that is known to have no thermal effects.
- Both are placed in a heating chamber.
- The temperature is controlled by feedback system.
The sample and reference sample are heated or cooled at a controlled rate.
The difference in heat flow is measured by the thermocouple.
If the sample is pure it will show a well-defined melting point or temperature confirming its purity.
If the sample is impure, the transition will be broadened and will show impurities.
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- Year 3 Advanced Analytical Science Flashcards Karteikarten am AAS Flash, erstellt von Legend of LOTR am 07/05/2023.
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