Separation of Toludene isomer by Ion pair chromatography

[praveenpaliwal]

Hellow every body,

I am doing the work of the separation of toludene isomer by ion pair chromatography. I used 0.01M Heptane sulfonic acid Na salt + 0.01M KH2PO4 and adjust the pH of this solution 2.0 by H3PO4. I used acetonitrile as Organic solvent with ODS-3 column. I got good separation in O and M isomer but P-Iosmer is co-eluting with M-Isomer.
I also use THF + methanol : : 50 : 50 as organic modifier and buffer is same as above with same ODS-column.
Now any body tell me effective ion pair method for the separation of these isomer. I do not have SELIC column that's why I want the clue on ion pair only.

Best regards

Praveen

[Gerhard Kratz]

As Uwe Neue stated in an earlier reply to a similar post, he would start with a standard Si column and normal phase conditions, and I agree.
Here are the standard chromatographic conditions for a Si column. Good luck.
det.: UV at 245 nm
flow rate: 1.0 mL/min.
injection: 10 μL
mobile phase: 96:4, hexane:2-propanol
sample: 50 μg/mL each in mobile phase
temp.: 35 °C

[HW Mueller]

Is this suposed to be toluidines?

[praveenpaliwal]

Yes it is Toluidines ?

Should I use X-terra clumn for that???

Praveen

[ym3142]

i do not have experience on these isomers.

IF it were me I would start with C18 with regular RP MP, instead of IP.

I do not see how IP can help. IP helps if IP interact with the isomers differently because of ion-ion. Unless you want to try a MP pH close to their pKa (~4.5)

I feel the difference of eletronic effect and steric effect are great among them.

If not, some phenyl column should help, where pi-pi interation may differ.