Question | Answer |
What governs the distribution of the solutes between the aqueous phase and the organic phase? | Their relative solubilities |
How can one ascertain whether a layer is the organic phase or the aqueous phase? | Add a drop of the mystery layer to 2 mL H2O; if it dissolves, it's aqueous; if not, it's organic |
Why must extraction mixtures be vented? | Organic solvents are volatile and evaporate quickly, generating pressure inside the separatory funnel |
What three advantages are associated with the thin-layer chromatographic technique? | 1) very small sample quantities are required, 2) great ease and rapidity with which experiment's performed, 3) good resolution's often obtained |
What two limitations are associated with gas-liquid chromatography? | 1) analysis is limited to small amounts of sample, 2) samples must consist of reasonably volatile compounds |
What are the six basic parts of a gas-liquid chromatograph? | 1) source of high-pressure pure carrier gas (e.g., helium or nitrogen), 2) gas flow controller, 3) heated injection port, 4) column and column oven, 5) detector, 6) recording device or data station |
What three pieces of information are provided in the data table of a gas chromatogram? | 1) peak retention times, 2) peak areas, 3) percent compositions |
What must be available in order for GC analysis to permit compound identification? | Authentic samples of the various components in the mixture being analyzed |
What are the six items that must be determined in order to establish the sequence of a peptide (or protein)? | 1) cleave all disulfide bridges and alkylate resulting thiol groups, 2) determine constituent amino acids, 3) identify N-terminal aa, 4) identify C-terminal aa, 5) fragmentation through partial hydrolysis, 6) identify locations of any disulfide bridges |
What conditions are employed to "completely" hydrolyze a peptide? | Digest peptide in 6 M HCl at 100 degrees C for 24 hours |
An enzyme that catalyzes the hydrolysis of a peptide bond at the end of the peptide chain is called? | Exopeptidase |