Chromatography Forum

Hi
my problem is the separation of 1-bromo-3,4-Dichlorobenzene and its isomer 1-Bromo-2,4-Dichlorobenzene on GC FID. I tried Various Types of Column with Various Conditions Columns are DB-17,DB-1701,DB-WAx, Ultra-2,Ulbon-HR 1 (50Meter) , CP-Wax(60Meter) , DB-5MS,CP-SIL5CB. I found these isomers separation on CP-SIL5CB on GC-MS with 20ppm only. If anybody have the idea about this type of isomer separation please suggest me.
thanks in advance.

Ask the supplier of your chemicals the GC test they use to determine purity.

best wishes,

Rod

Thanks ,
but we are manufacturing this and our customer says about this impurity they also send the chromatogramm but not the condition.

Can you not ask your customer for their conditions?
WK

Dipole or boiling point mechanism for the separationi is likely very weak.
A physical size mechanism is the better solution in my opinion (guess).

I would suggest a cyclodextrin column like the G-TA Astec column from Supelco.

But I do not have any definitive data to confirm the separation.

I would ask their technical service if they have any suggestions.

best wishes,

Rod

Thanks for this
we already asked to customer but still customer take time for this and we want to established this on our condition.
again thanks to rod for valuable suggestion.

Just a thought, another suggestion might be a long packed column 20-30ft of 1% Carbowax 20m on Carbopack B 80/120 in fused silica SS. Another suggestion would be 5% Krytox AC on Carbopack B.

Would you share your customer's analysis with us? I am curious concerning the separation. I would have thought OV-17 or Carbowax 20M would have done a better job at separating these isomers.

Best wishes,

Rodney George
Supelco

Mr. Soni,

I am a bit surprised by the inability of the wax to separate these components. I found an application note for a 30 meter X 0.53 X 1 micron film wax that shows the dichlorobenzene's separated over about 1.5 minutes with at least 20 seconds between the 1,3 and the 1,4 so I am a bit surprised that your 60 m. did not do the job. Perhaps the parameters are not conducive?

Rod's suggestion about a cyclodextrin column would be my next suggestion but one other thing you might try is a cyanopropyl column such as the BPX-90 which is considered very polar.

Best regards

Thanks for these valuable suggestion.
Presently we are analysing the Compound on DB-17 and we found to Dichlorobenzene Isomer and two Isomers of Bromodichlorobenzene on this column then we tryed many different Conditions on this column butwe can't find the separation and then we tried Other columns. but i think rod is right we just tried on one or two conditins only and then change the column.
again thanks for your valuable suggestion.

Dear AICCM

First of all thanks for your confidence on wax column.
i also separated the dichlorobenzene isomers on wax and DB-17 and DB-1701 but my compound is Bromo 3,4-Dichlorobenzene and its isomer Bromo2,4-dichlorobenzene. we also separate the isomer Bromo3,5-dichlorobenzene. we also tried the column BPX-70 and we can't find separation.

Finally i found all the isomers on HPLC . and now the chepter is closed