
 Posts: 6
 Joined: Thu Jan 12, 2017 1:43 pm
Hi guys,
I'm having trouble answering this question after a practical i did on reversed phase HPLC and was wondering if perhaps any of you could help me.
Qs; "The retention in this form of chromatography can be approximated by the equation:
log k = log k(w)  S theta
where theta is the volume fraction of organic solvent in mobile phase
k = retention factor
k(w) = a constant related to the retention time of the substance if pure water was used as mobile phase
S is a constant for the compound on a given column with a given binary aqueous/organic mobile phase
Explain whether this eq holds for your results by plotting an appropriate graph for toluene? If so, use the graph to estimate the retention time of toluene in 40% methanol/ 60% water."
No values for the constant have been given and have one chromatogram of Toluene with mobile phase of 80% methanol/20% water and came out with a retention of 3.323
70%3.358
90%2.379
uracil unretained 1.484
If anyone can give me any pointers on how to tackle this I would be very grateful as I really have no idea at the moment
I'm having trouble answering this question after a practical i did on reversed phase HPLC and was wondering if perhaps any of you could help me.
Qs; "The retention in this form of chromatography can be approximated by the equation:
log k = log k(w)  S theta
where theta is the volume fraction of organic solvent in mobile phase
k = retention factor
k(w) = a constant related to the retention time of the substance if pure water was used as mobile phase
S is a constant for the compound on a given column with a given binary aqueous/organic mobile phase
Explain whether this eq holds for your results by plotting an appropriate graph for toluene? If so, use the graph to estimate the retention time of toluene in 40% methanol/ 60% water."
No values for the constant have been given and have one chromatogram of Toluene with mobile phase of 80% methanol/20% water and came out with a retention of 3.323
70%3.358
90%2.379
uracil unretained 1.484
If anyone can give me any pointers on how to tackle this I would be very grateful as I really have no idea at the moment