D L1: Sample Preparation Flashcards
what are the different types of biological samples?
Blood Tissue Urine Vitreous humour cerebrospinal fluid
what molecules are found in biological samples?
Deoxyribonucleic acid (DNA)
Proteins
Lipids
Metabolites
what is sample extraction?
term used to describe the removal of the analyte from a matrix
what is sample digestion?
term used to describe the destruction of the matrix to release the analyte
whats the extraction equation?
(analyse)p1 arrow (analyse)p2
How can equilibrium be changed?
by heat and solvents
what’s a partition ?
analytes moving from one phase to another without any chemical changes
what can k equal too ?
K= [𝐴𝑛𝑎𝑙𝑦𝑡𝑒]𝑃2/[𝐴𝑛𝑎𝑙𝑦𝑡𝑒]𝑃1
what is k?
‘K’ is a ratio of the concentration of the analyte in Phase 2 to Phase 1
Value of K depends on ______ of the analyte for each phase
affinity
what are the phases?
Polarity (“like dissolves like”) Volatility (headspace) Hydrogen-bonding interactions Ion-ion interactions Ion-dipole interactions Dipole-dipole interactions
when you have the structure of your analyte what can you guess?
guess at predicting its polarity and hence choosing an appropriate solvent system
polarity of organic molecules are ….
dictated by their functional groups
Functional groups contain …..
contain polarised bonds which make the compounds polar
whats headspace?
partition between liquid and gas
whats Passive headspace
?
Equilibrium is constant or not disrupted
whats Dynamic headspace ?
Equilibrium is disrupted (arrow) analytes driven into gas phase (or vapour phase)
when is headspace analysis useful?
the separation of most volatiles from non-volatile liquids/solids
what equipment is neededd for headspace analysis?
airtight container
airtight syringe
what is the sample in headspace analysis?
vapour in the space above the liquid
whats LLE?
liquid liquid extraction
what does LLE give a measure of?
hydrophobicity
whats the LLE equation?
KOW = [Analyte]octanol/[Analyte]water=[A]o/[A]w
what usually reported from LLE?
Log Kow
Octanol and Water are not _______
micible
if log k ow is less than zero whats the phase?
hydrophilic, more in aqueous phase
if log k ow is equal to zero whats the phase?
equal distribution between two phases
if log k ow is greater than zero whats the phase?
hydrophobic (lipophilic), more in organic phase
what can blood be classed as?
tissue
can drugs be found in tissue?
yes
How is the protein removed form the tissue?
removed by precipitation
what are the 3 main methods of percipitating protein?
Organic solvents
Salting out
Isoelectric point
what stops a protein from aggregating?
hydrophilic amino acids on surface create a hydration sphere
how does organic solvent precipitation work?
- needs to be miscible in water
- disrupts hydration sphere
- proteins aggregate
how does salting out precipitation work?
- add electrically neutral salt to sample
- reduces hyrdatation sphere, increases protein-protein interaction
- [rotein aggregates
How does isoelectric point precipitation work?
- diff value for proteins
- adjust pH with acid/base
- isoelectric point forces cancel out
- attractive force dominates, protein aggregates
- selectively remove proteins
Volatiles in a liquid (or solid) can be extracted using …..
Liquid (solid)-Gas extraction
Non-volatile analytes can often be extracted by ?
liquid-liquid extraction or by removal of the proteins
