Chromatography Forum

Hi everybody!
I'm new here and found this forum very very interesting.
Can I ask you if anyone has ever worked on Lomustine?
My task is to develop a HPLC impurity method. Maybe you can give me a hand.

Thanks a lot,

E

Hi everybody..

Could you please give me some advice about this issue?
I've been working on this nitrosourea compound as I said in the previous post. I've got good results sp far but I hace a big problem.
One of the possible degradants is a primary amine (cyclohexylamine) and I can't make it to detect it with my reversed phase method, even if I use my UV detector (the only one I have) at 195nm. I can see ir when I use a high concentration and, anyway, the peak's got a horrible shape. I've tried to use a low pH buffer (2.1)-phosphate- and the peak shape got better-nevertheless, the sensitivity is still bad.

Can anyone help?

What do you need to attain as a detection limit (in mass units)? Cyclohexylamine doesn't have much of a chromophore and UV may simply not be sensitive enough.

Tom,

Thanks a lot for replying.
It should be as low as 0.1% or something similiar. I still don't know and have to ask but a rough idea this is so.

I have to make my boss understand that maybe we have to develop a different method for cyclohexylamine (maybe a GC or TLC method).

What do you think?

I was also thinking of asking for a conductivity detector.
What is your opinion?

Thanks,

E

You have to define your target sensitivity in terms of mass-on-column, not %.

That said, it really doubt that conductivity will be much better than RI. GC or fluorescences (both would require derivatization) would be a better bet.

To perform a limit test by TLC might be a good idea.

You should be able to determine if CHA is present at 200, 500 or 1000 ppm.

A TLC test might only take a few minutes if you use reverse phase TLC and Ninhydrin or Iodine could give you an answer you seek.

best wishes,

Rod

Thank you guys!

I'll do some trials and will let you know.

I think RID and TLC will be the first ones. I have to find a RID detector, first! Do I have to avoid certain buffers or solvents using RID?

I will let you know.

Thanks a lot.

Hi everybody,

I have one question.
I'am doing some trials on RID detector but also want to try a derivatization agent. I need to buy one and thought of OPA.
What is your opinion? I have to derivatize a primary amine.
I can only use a UV detector. I think there the derivate will not lack absorbance in UV.
Has anyone of you ever worked with this reagent?
How would I have to carry out the derivatization reaction?

Thank you for your help.

A very convenient reagent for this type of application is the ACCQ-Tag reagent from Waters. It reacts within seconds to a derivative that can be used with both UV and fluorescence detection.

I would try the HPLC derivatization method first-sounds the best approach.

The related compound dicyclohexylamine is used as a component of the Grob test mixture in GC. It is a sensitive test of column activity...so is not an easy compound to analyse. Of course, this is a secondary amine, but it could suggest that a GC method is not impossible for cyclohexylamine.

Just another suggestion.

Thanks a lot Guys!

Actually, I have been asked to develop an HPLC method.
So, I can't use a GC. Of course, Victor, in case there is no chance to detect it through HPLC I will turn to GC or TLC.

Uwe,
I'll have a look at Waters for your reactant.


Thanks for these advice.

Echolyns.