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56 Cards in this Set
- Front
- Back
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How can you get from diazepam to oxazepam? |
Diazepam (CYP3A4) -> Temazepam (CYP2C19) -> Oxazepam OR Diazepam (CYP2C19) -> Nordazepam (CYP3A4) -> Oxazepam |
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Which enzyme catalyses the conversion of codeine into morphine? |
CYP2D6 |
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Why do molecules with a chiral centre display two signals? |
Because they exist as stereoisomers around the alpha carbon |
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What happens during chromatography? |
Mixture in the mobile phase reacts with the molecules in the stationary phase, which causes separation |
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What are the five different types of chromatography? |
-Adsorption -Partition -Ion-exchange -Gel permeation -Affinity |
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What are the features of adsorption chromatography, and what are some examples? |
Stationary phase is solid (eg: silica, alumina)
-TLC -Column |
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What are the features of Partition Chromatography and name an example? |
Both stationary and mobile phase are liquids -HPLC |
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What is the main feature of Ion-Exchange Chromatography? |
Stationary phase is an ion-exchange resin |
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What is Gel Permeation Chromatography? |
Size-exclusion chromatography: Separation based on size of gel particles, the smaller particles are separated from other particles. |
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What is Affinity Chromatography? |
Ligand immobilised on solid, stationary phase |
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What happens during TLC? |
Silica stationary phase: non-polar compounds eluted first and will travel further up the plate. QUALITATIVE |
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What can you use to visualise TLC? |
-UV -Iodine -Sulphuric Acid -Molybdate |
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What happens during 'Lab-Scale' Column Chromatography? |
-Separation of organic compounds on an inert stationary phase -Column packing method can affect results -Gravity columns driven by the solvent head -Have to do TLC first-> not analytical |
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What are the different types of Quantitative Analytical Techniques? |
-Gas chromatography or High performance liquid chromatography (mobile phase can be a gas or a liquid) |
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What happens during Quantitative Analytical Techniques? |
Analytes are separated based on differing affinities for the stationary and mobile phases. |
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What does the small peak on a chromatogram represent? |
The peak due to the solvent |
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What does t0 stand for on a chromatogram? |
Dead time- the time it takes for the dead volume to get through, before the sample enters |
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What does tr stand for on a chromatogram? |
Retention time-> the time for the material to travel and leave after injection |
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What does the large peak represent on a chromatogram? |
The signal of the analyte |
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Where do you measure the width on a chromatogram, and what does this give you? |
-Measure width at half height (W0.5) -Gives you the resolution |
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How can you quantify data from a chromatogram? |
Measure the peak area under the signal |
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What does k stand for on a chromatogram? |
Retention factor: tr-t0 k= -------- t0 |
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What does α stand for on a chromatogram? |
Separation factor: k2 tr,2-t0 α= ----- = --------- k1 tr,1-t0 |
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What value must the separation factor, α, be in order to achieve separation? |
Greater than 1. |
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What happens if the separation factor, α, is less than 1? |
You get overlapping peaks that don't go to the base line. |
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What does N stand for in Chromatography? |
Column efficiency/ Plate number |
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What does a higher N value represent? |
A narrower signal and therefore a better resolution, due to more plates |
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What does As stand for in Chromatography? |
Asymmetry factor b As= ---- a Measure a and b at 10% of peak height (a= width of left side, and b= width of right side of curve)
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What is the acceptable range for the asymmetry factor? |
0.9->1.2 |
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What does an As >1 mean? |
Graph is tailing |
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What does an As <1 mean? |
Graph is fronting |
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What does R stand for in chromatography? |
Resolution (A quantitative measure of separation) |
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What three things must be met to achieve resolution? |
-Peaks retained on column, K>0 -Peaks separated α>1 -Column must develop a minimum limit of N |
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What are the steps of Gas Chromatography? |
-Sample is injected onto column -Column heated to release volatile components -Mixture separated on the column and detection methods used |
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What are the steps of High Performance Liquid Chromatography? |
-Sample injected as solution on to the column -Mobile phase flows constantly through the pump, column and detector -Injection valve introduces the sample to this flow -Mixture separated on the column and components detected |
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What does typical HPLC apparatus consist of? |
Mobile phase reservoir, high pressure pump, injection valve, sample loop, column and detector |
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What are the features of HPLC columns? |
-Stainless steel to withstand high pressures and wide range of solvents -!0cm in length with an internal diameter of 4.6mm -Stationary phase packed under high pressure -Stationary phase made of silica particles with 5mm diamter (as small as 1.7microm) |
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What is reverse phase HPLC? |
Where silica has been modified to make it less polar, by the addition of C18 alkyl groups to the silica surface (octadecylsilyl, ODS) |
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What causes a higher retention time in HPLC and why? |
A higher Log P of the molecule: it interacts with the ODS stationary phase more |
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What causes a lower retention time in HPLC and why? |
A lower Log P of the molecule: it interacts with the ODS stationary phase less |
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When is poor retention/peak shape observed in RP-HPLC? |
When using ionised analytes |
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In what form should a molecule predominantly be for analysis with RP-HPLC? |
A non-ionised form |
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How can you ensure that 90% of an acidic analyte is in the non-ionised from? |
Adjust the pH of the mobile phase to 1 pH unit below the pKa of the analyte |
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What is the effect of pH on a basic analyte during reverse phase HPLC? |
Retention factor reduced at low pH (ionised) Retention factor increased at high pH (unionised) |
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What is the effect of pH on an acidic analyte during reverse phase HPLC? |
Retention factor increased at low pH (unionised)Retention factor reduced at high pH (ionised) |
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What are the six different type of detectors you can use after chromatography? |
-Mass Spectrometry -Flame Ionisation -UV/Vis detector: flow-through cell -Diode array detector: flow-through cell -Fluorescence detector: flow-through cell -Apparatus linked to some other means of analysis |
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What things is HPLC used for? |
-Drug discovery -Pre-formulation -Impurity testing of API and excipients -Formulation -Quality Assurance testing -Pharmacokinetic and drug metabolism studies -Separation and quantification of chiral API isomers |
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What are the three different hyphenated techniques? |
GC-MS LC-MS MS-MS |
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What is LC-MS |
-HPLC coupled with mass spectrometry -More difficult than GC because analyte already in inert gaseous phase -Mobile phase must be removed before MS -Analyte/s ionised prior to entering MS |
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When is LC-MS used? |
When the identity of the analyte is unknown, or it shows poor intensity using other detectors |
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What are the five different soft ionisation techniques? |
-Chemical Ionisation (fragmentation) -Fast Atom Bombardment (FAB) -Electrospray Ionisation (ESI) (No vacuum) -Matrix-Assisted Laser Desorption Ionisation (MALDI) -Atmospheric Pressure Chemical Ionisation (APCI) |
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What is the Molecular Ion on a mass spectrum? |
-The radical cation formed from the compound of interest -The highest observable ion, but not the most intense peak |
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What is the base peak? |
The peak with maximum intensity, 100% |
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What is the nitrogen rule? |
Even m/z molecular ion = even number of N
Odd m/z molecular ion= odd number of N |
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Front (Term) |
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