(C), could also be used, but comes with a risk of rendering the titin unusable; the eluent run
through an affinity chromatography column often binds to the target molecule.13 . B
Each of these is the mobile phase of the system, in which the solutes are dissolved and move. The
stationary phase in gas chromatography is usually a crushed metal or polymer; the stationary
phase in paper chromatography is paper.
14 . C
Warm or hot solvent is generally used in gravity filtration to keep the desired product soluble.
This allows the product to remain in the filtrate, which can then be collected. In this case, the
student likely used solvent that was too cold, and the product crystallized out. The product
should be present in the residue.
15 . B
Because the lactoferrin proteins are likely to be charged, as is the resin described in the question,
this is an example of ion-exchange chromatography. The charged protein molecules will stick to
the column, while the remainder of the milk washes through and can later be washed off of the
column and collected.