HPLC System set up and shut down

[StephenO]

What are peoples procedures when setting up and washing down HPLC Systems i.e. what solvents should be used for reverse phase columns and for how long? What should the system be flushed with before runs and after runs and for how long?

[lmh]

Personally I flush C18 and other "standard" columns with 70% MeOH or 70% ACN (no additives, no formic acid etc.) for 10 column volumes (or often just 20min on a standard "stop" method). If a manufacturer has specific instructions for their column, it's good to follow them, but when the ACN crisis was happening I checked with a major manufacturer that MeOH is fine as a storage solvent in silica-based C18 even though ACN was the recommendation. I don't use 100% in case there is any tiny residual amount of anything salty and insoluble in 100% organic, that might precipitate.

Most of our systems get sufficient use that we never have to put them into "storage" conditions, but would expect to replace aqueous solvent every couple of days (so no time for bugs to grow). Where we do leave things in storage, it's usually 20% MeOH or similar; enough organic to prevent bugs, but otherwise aqueous and no corrosive additives. Again, we want to avoid long-term precipitation of anything salty (e.g. in inlet filters, which are surprisingly difficult to rinse totally free of salt).