By Chris on Thursday, July 8, 2004 - 05:45 am:

We are currently looking at the possibility of purchasing an LC-MS for defining impurity profiles in method development and validation projects. How easy is it to adapt a LC-UV method to be run on LC-MS, and how does the precision of LC-MS compare with LC-UV, i.e. can LC-MS be suitable for QC assay analysis for low level actives?

Thanks

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By MG on Thursday, July 8, 2004 - 11:45 am:

Our requirements for LC-UV methods are 2% for precision, but 0.5% is typical of what you get. To compare, precision for a solvent standard in LC/MS usually ranges from 1% to 8% (without an internal standard). I'm afraid I don't know much about the requirments for dose formulations. For bioanalytical, the tolerances are usually much wider than that.

In general you should only use formic acid, acetic acid, and their ammonium salts, and ammonium hydroxide, for buffering. There are exceptions: TFA or TEA or other volatile additives can be used depending on the ionization mode. Phosphate buffers should not generally be used.