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forensic toxicology - analytical techniques - gas chromatography - Statistics
General Stats
- This quiz has been taken 5 times
- The average score is 5 of 48
Answer Stats
| Hint | Answer | % Correct |
|---|---|---|
| what is the mobile phase of gas chromatography? | a carrier gas such as helium or hydrogen | 80%
|
| what are the most common types of detector used in gas chromatography? | flame ionisation detector (FID) | 60%
|
| what is gas chromatography used for? | the analysis of compounds that can be vaporised (without decomposition) into a gas state | 60%
|
| it is then inserted into the injector of the gas chromatogram where the analytes are volatised | 40%
| |
| Quick | 40%
| |
| what is the most important parameter to consider in selection of the column for gas chromatography? | the polarity of the sample | 40%
|
| what is QuEChERS, and what does it stand for? | a multistep extraction process for sample preparation | 20%
|
| Cheap | 20%
| |
| Easy | 20%
| |
| Effective | 20%
| |
| extraction into a volatile solvent (e.g. methanol) | 20%
| |
| what does it involve? | initial extraction with solvent (acetonitrile) | 20%
|
| mass spectrometer | 20%
| |
| how does separation primarily occur in gas chromatography? | on the basis of differences in boiling point | 20%
|
| Rugged | 20%
| |
| Safe | 20%
| |
| thermal conductivity detector (TCD) | 20%
| |
| what is the most common column chosen for gas chromatography? | 5% phenyl 95% methyl-polysiloxane (5ms column) | 0%
|
| what does it involve? | a fibre coated with an extraction phase (e.g. liquid polymer or solid sorbent) | 0%
|
| what is the stationary phase of gas chromatography? | a layer of liquid or polymer contained within a column made of glass or metal | 0%
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| TCD | analyte elution causes a drop in thermal conductivity, that can be detected | 0%
|
| FID | as organic compounds elute, they are pyrolysed (incinerated) in the flame, forming cations & electrons | 0%
|
| chemical treatment | 0%
| |
| cleaning using dispersive solid-phase extraction | 0%
| |
| how do these work? | electrodes are placed next to a hydrogen or air generated flame at the end of the column | 0%
|
| how must samples be prepared for gas chromatography? | in a liquid or gas state | 0%
|
| what will choosing the appropriate column give you? | increased separation and resolution | 0%
|
| how does gas chromatography use temperature to separate the sample? | isothermal analysis (temperature stays the same) | 0%
|
| how does it work? | it injects the sample into a heated chamber | 0%
|
| it is inserted into a liquid or gas sample & analytes are extracted onto the fibre | 0%
| |
| partitioning using a salt mixture | 0%
| |
| what is the relationship between the rate at which the sample passes through the column and the temperature of the column? | proportional | 0%
|
| what is SPME? | solid-phase microextraction | 0%
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| which part of the inlet pushes all the sample into the column? | splitless (split mode is used to analyse only part of the sample (e.g. 10%)) | 0%
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| what are the most common type of inlet in gas chromatography? | split/splitless (S/SL) inlet | 0%
|
| what is derivatisation? | the addition of non-polar groups to a molecule to reduce its boiling point | 0%
|
| the carrier gas (e.g. Helium) sweeps the sample into the column | 0%
| |
| then | 0%
| |
| what is the inlet of gas chromatography? | the syringe that injects the sample into the gas flow | 0%
|
| they need to be volatile at the temperature of the inlet (e.g. 300°C) | 0%
| |
| this causes | 0%
| |
| FID | this generates a current between the electrode, that is detected | 0%
|
| what is the purpose of a column oven? | to maintain precise temperature control | 0%
|
| what does derivatisation allow us to do? | use gas chromatography on molecules that would otherwise not be possible | 0%
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| using a temperature gradient (most common method) | 0%
| |
| how do we perform data analysis? | using the peak area of a chromatogram | 0%
|
| how do we achieve this if the samples do not meet these requirements? | vaporisation | 0%
|
| volatisation of the sample | 0%
|
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