QUESTION 1
What is are the differences between frontal and displacement chromatography?
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QUESTION 2
You load a chromatography column with a solution whose concentration is c0 at time 0 in the form of a step change. Assuming that the column resin reaches equilibrium fast enough compared to the flow, what will be the saturation value of the resin. The Langmuir isotherm is valid with the maximum loading of qm and the binding affinity constant is K0.
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QUESTION 3
In the above example, if the total column volume is V0 and the gel has been estimated to have an overall density in the column of r_gel (including the intergel void space), determine the amount of solute adsorbed.
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QUESTION 4
A Gaussian peak was determined in a chromatography pulse experiment. The peak had a width of 4 mL (volume). The mid-point of this peak occurred at a volume of 75 mL. Determine the HETP for this column based on the van Deemter equation if the column length was 75 cm.
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QUESTION 5
Which chromatography do you bind at low salt and elute at high salt? Explain why? In what cases would you reverse this?
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QUESTION 6
Explain the principle of size exclusion chromatography and where it is used.
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QUESTION 7
Explain the difference between a cocurrent and a countercurrent cascade. Which one is more effficient and why?
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QUESTION 8
Explain the concept of critical flux in membrane filtration.
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QUESTION 9
What is limiting flux in ultrafiltration?
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QUESTION 10
Explain membrane fouling in microfiltration. How can you control it?
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Part B
QUESTION 1
A laboratory column separating a plant protein showed a linear breakthrough curve with a slope of 1/15 min, centered about 30 min. If the column was 1 cm in diameter and 10 cm in height, and the feed flow was 1 ml/min, what will be the breakpoint time in a column that is 1 m in diameter and 2 m height?
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QUESTION 2
Recently a system of Polyethylene Glycol and Poly Acrylic Acid (PAA) have been investigated as aqueous two phase systems. The following data were obtained to determine the binodal curves.
Plot the data in a phase diagram showing the binodal curve.
Fit the curve to a hyperbolic equation and determine its constants.
The partition coefficient of BSA (protein) as given as a 2nd order polynomial in the tie-line length. Give an expression for the partition coefficient.
0.1
0.9
0.2
0.8
0.3
0.7
0.4
0.6
Tie Lines – x coordinates given above for the two end points.
0.1
0.944297
0.2
0.294752
0.3
0.17463
0.4
0.124068
0.5
0.096211
0.6
0.07857
0.7
0.066396
0.8
0.057488
0.9
0.050688
x
y
QUESTION 3
Sometimes adsorbents are used to strip low level contaminants from a product solution. One such is a soluble surfactant called C-TAB (cetyl- Trimethyl Ammonium Bromide) which is cationic. If an ion exchange column is to be used for stripping CTAB from an aqueous solution, determine the bed capacity given the following: bed volume = 20 l; Stot = 16 mg/ml; Keq = 20 ml/mg and CTAB is at 52 ug/ml (micro-grams). Plot this bed capacity as a function of CTAB concentration in the feed solution for inlet concentrations between 1 ug/ml and 100 ug/ml.
QUESTION 4
Laboratory filtrations were conducted by applying constant pressure to filter a cell lysate suspension along with filler particle materials. The filter area was 880 cm2, the mass of solid per unit volume of filtrate was 47 g/l and the temperature was 20 C. Evaluate the specific filtration resistance and the medium resistance given the following data of filtrate volume at different times. The applied pressure was 1 atg.
Time, s
5
11.5
19.8
30.1
42.5
56.8
73.0
91.2
111
133
V, l
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
During production, it was found that the specific filtration resistance increases
due to compression of the cake. The pressure in the production unit is 2.5 atm(g)
and the filtration resistance is a power-law function of pressure drop with the
power index of 0.30. Determine the new cake resistance under the production
conditions.
QUESTION 5
A pilot disc-stack centrifuge (Alfa Laval Model BTPX 205) is being used for cell harvesting of E. coli, which has a diameter of nearly 1 μm. For intracellular product recovery after cell disruption this centrifuge can be used to remove most of the cell debris particles before proceeding to further product purification.
Highly expressed foreign proteins in E. coli form inclusion bodies that have a Stokes’ diameter of 0.5-1.7 μm and a density of 1.4 g/cm3. The high density of inclusion bodies allows them to be separated from most cell debris particles using a disk-stack centrifuge. By running the centrifuge at an appropriate throughput, almost all of the inclusion bodies are recovered in the heavy phase of the centrifuge while most of the cell debris particles remain in the light phase.
What effective area (Σ) is necessary for E.coli recovery if the disk-stack centrifuge throughput is 300 L/hr?
At what throughput would you run the centrifuge if you wanted to separate inclusion bodies from cell debris?
Assume that the broth viscosity increases by a factor of 2 after cell disruption because of the release of nucleic acids & state all your other assumptions.
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