Sub ppm analysis using hplc

[Santosh Gandhi]

Hello,
Recently regulatory authorities have been insisting in the analysis of potential genetoxic impurities in drug substances.The limit for these impurities is very low usually around 0.15µg/g of drug substance depending upon the daily dosage. Determination of impurities at such low level using HPLC/UV (of course some analysis can be done using LC-MS,but I have to carry out using HPLC/UV so that the analysis can be transfered to QC) is proving to be difficult if the drug substance as low solubility.Even if it is soluble it is overloading the column and causes its collapse. I request any of you who as experience in such analysis to give your suggestions. Thanking you,
Santosh Gandhi.

[Bruce Hamilton]

Given the relative difficulty and sensitivity, I doubt very much that any HPLC-UV method is going to be suitable, even for process control.

My experience with trace cytotoxic residues was that that other compounds almost alway invariably interfered, giving false positives.
The samples then had to be analysed by a specific method, eg LC-MS-MS. When concentrating samples, you have to ensure that you don't lose/modify the genotoxic compounds.

I think you have to look to LC-MS-MS, or similar. But this analytical area is going to grow very quickly, and really is likely to be a mixture of "biological activity " tests and sensitive chemical tests. It may be even more lucrative for instrument makers than the melamine scandal.

For those curious, the Dec 2008 FDA guidance is at
http://www.fda.gov/cder/guidance/7834dft.pdf
The earlier EU one is at..
http://www.emea.europa.eu/pdfs/human/swp/519902en.pdf

There may be later versions, I haven't checked.

Please keep having fun,

Bruce Hamilton