Chromatography Forum

Good morning to all
In ICH Guideline for n-Hexane limit is 290 ppm. Where in commercial hexane which is using as solvent has 5 isomers namely 2-Methyl pentane, 3-Methyl pentane, n-Hexane, Methyl cyclopentane and Cyclohexane. In the above 5 isomer n-Hexane and Cyclohexane limit only given in ICH. How we can perform for the remaining isomers in Residual solvent analysis, and which limit can i follow for that. I have perchance sigmal aldrich standard for all the above standards. Can any one help me.

I would make the gross assumption that the limit for each of the isomers is the same due to the similarity of chemical nature of each isomer.

Since FID responds approximately equally to all of these, I would sum up the response of the isomers and treat it as if it were all hexane.

My take on the problem.

Rod

Hi

Have been in a similar situation and I agree with Rod. I would use a limit for "total hexane and related isomers" based on the ICH limit for n-hexane, the limit for cyclohexane is way higher.

However I would double check tox data so that none of the isomers apart from cyclohexane is considered more toxic.

I am uncertain if the traditional residul solvents columns in pharmacopieas (Wax or 624) will resolve all isomers, perhaps the 624. Our case was not identical but if memory serves we had to use a more non polar column a -5 or -1.

Also if memory serves DMF is a better solvent than DMSO for alkanes.