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- Posts: 175
- Joined: Thu Jul 26, 2007 2:13 pm
I feel a little dumb asking this since I think I should know the answer, but since my anonymity is guaranteed I'm going to ask anyways.
We have two sets of positional isomers that I have to separate. The two sets are identical in structure except that one set of R and S isomers has a NO2 group and the other set has been reduced to NH2.
The NO2 isomers were separated using a Chiracel-OJ column with conditions 80:20 hexane:IPA, sample diluent EtOH, column temp. 40°C, flow rate 1.0 ml/min, back pressure 40 bar. The isomers are baseline resolved with very good looking sharp gaussian peaks.
Using the exact conditions for the NH2 isomers, the peaks were resolved but extremely broad in shape. They're not taling to be clear, just very low plates. What is the mechanism for this? I'm aware that compounds that are strongly retained will tail, but tailing is 1.0 here. The peaks are just very very broad. 6-7 minutes wide.
If I was trying to deal with a tailing problem, I could add DEA, but I don't think I'm ever had to address poor efficiency before. thanks for any suggestions.
We have two sets of positional isomers that I have to separate. The two sets are identical in structure except that one set of R and S isomers has a NO2 group and the other set has been reduced to NH2.
The NO2 isomers were separated using a Chiracel-OJ column with conditions 80:20 hexane:IPA, sample diluent EtOH, column temp. 40°C, flow rate 1.0 ml/min, back pressure 40 bar. The isomers are baseline resolved with very good looking sharp gaussian peaks.
Using the exact conditions for the NH2 isomers, the peaks were resolved but extremely broad in shape. They're not taling to be clear, just very low plates. What is the mechanism for this? I'm aware that compounds that are strongly retained will tail, but tailing is 1.0 here. The peaks are just very very broad. 6-7 minutes wide.
If I was trying to deal with a tailing problem, I could add DEA, but I don't think I'm ever had to address poor efficiency before. thanks for any suggestions.
