Lomustine

[echolyns]

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

[echolyns]

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?

[tom jupille]

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.

[echolyns]

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

[tom jupille]

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.

[chromatographer1]

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

[echolyns]

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.

[echolyns]

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.

[Uwe Neue]

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.

[Victor]

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.

[echolyns]

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.