Toluidine positional isomers trace analysis

[avitan]

Hello, all!

I need advice in following problem:

I have to separate 3 positional isomers of Toluidine (o-,p-,m-), than I have to do their trace analysis, i.e. m- and p- isomers (at 0.1% level) in o-Toluidine (100%).

Up to this point I have succeded to resolve o-Toluidine from m-Toluidine (on C-18 stationary phase with subambient temperature), but p-Toluidine trace still eluted under the o-Toluidine main peak

Maybe there is some other technique (CE ?), I'll appreciate any suggestion.

[SIELC_Tech]

You can play with buffer nature and try to adjust pH hoping that you can get separation. You can try to use phenyl column and add pi-pi interaction.

Another approach is to add ion-exchange interaction with mixed mode approach. The general scheme is described here:
http://www.sielc.com/Technology_2D_Properties.html
You are using 2-D approach on a single column. I will try to see if we can do this for you first week of January. We have similar application for the separation of aminobiphenyls:
http://www.sielc.com/compound_188.html
In your case I would go either with Primesep 100 (reverse phase and ion-exchange) or Primesep P (reverse phase, ion-exchange and pi-pi interactions) column.

You can also use GC.

Regards,

Vlad

[avitan]

>>Mixed mode
Thanx a lot for a hint, it might be interesting
>>GC
No separation on GC achived (yet)

[Uwe Neue]

This separation should be rather straightforward on a silica column with normal phase chromatography. This is where I would have started with this task.

[Mark]

Another excellent choice is to use a graphitized carbon column, these easily separate the named isomers.

Regards,
Mark

[avitan]

Uwe and Mark, thanks a lot for your advice, i'll update this topic with results...

[avitan]

Another excellent choice is to use a graphitized carbon column, these easily separate the named isomers.

Regards,
Mark

Mark, would you, please, provide me some reference or start-point, i've had no experience with this type of stationary phase

Thanx in advance

[Bill Tindall]

I would do it by GC

[SIELC_Tech]

Avitan,

I ordered toluidines. If we get compouns this week you will have a method in couple of days.

Vlad

[avitan]

That would be wonderful, Vlad

Bill, thank you for your input, we didn't achived positive results on GC yet...[/b]

[Srinivas SK]

Hello

I think you'd get good results with pre-column derivatisation, using OPA and a C18. You need to use a gradient of course, but you will get baseline separation of o-,m- and p- isomers - within 20 minutes is my guess.

Usually OPA requires fluorescence detection, but in this case, a UV should do. Detection at around 340 nm.

If you try this out, I'd be very happy if you could share the results with me.

Best rgds,

[avitan]

...using OPA and a C18. ...

1. What OPA is?
2. I'll have to check recovery for derivatization process, am I?

Thanx for your input Srinivas SK

[Srinivas SK]

OPA = orthopthalaldehyde. Derivatising reagent used for primary amines. Usually meant for the HPLC analysis of, but not restricted to, amino acids. OPA-derivatives are fluorescent and can be detected at low levels.

Check out this link:

http://www.sigmaaldrich.com/img/assets/ ... 2_new_.pdf

This should answer some of your questions.

Best rgds,

[avitan]

Srinivas SK, thank you for this link, I'll consider this option

[SIELC_Tech]

Hi Avitan,

My two messages to you email bounced back. We have a method for you and I will publish a link as soon as we place the method on our website. We achieved very good separation with 3-5 minutes between peaks (150 mm Primesep 200 column).

regards,

Vlad