Does anyone know of an HPLC method that is equivalent to the USP method for stability-indicating analysis of human insulin samples? The USP method has a horrible mobile phase containing sodium sulfate and phosphoric acid at a low pH- it eats away at the metal components of the HPLC and forms stalactites off my columns. My C18 column is dead in a week. I have heard that most people qualify an in-house method and avoid the USP method, but I have had limited success discussing this with column manufacturers.

There is a European standard method. It might be worth checking

We did. It's the same method as the USP method.

We do a huge amount of assays using this method, or something very close to it. We use Perkin Elmer 200 HPLC machines. The main problem with this mobile phase is that it damages pump seals quickly which therefore need replacing frequently.
Retention time drift of the main insulin peak is also a problem, so the mobile phase needs to be made up very carefully. Giving the column a good clean at the end of the run will prolong its lifetime and give the machine plenty of time to equilibrate - 1 hour or more (all common sense I suppose). Finally use a Peltier autosampler as the samples degrade during the analysis and a mathematical correction is required. It is not much of a method, but with perserverance can be made to work satisfactorily.
Peter Osborne, Nottingham. UK

Thanks, Peter. Wow, I'm glad someone else has the same challenges with this method as I do. I guess folks just live with it and do the best they can. Are you using a specialized column? I just evaluated the Waters XTerraMS C18 for this application (it's supposed to be good down to pH 1.0) and didn't find a huge increase in column lifetime. I am typically getting about 110 injections of about 1 hour each out of a column. Because I run so many samples this translates into one $450 column per week, which the finance folks here are not happy about. How do you wash your colums? I've tried everything from 100% water to a water:Acn mix with no great increase in lifetime. I typically set the HPLC to an automatic rinse mode at the end of each run. Any further tricks to this?