How can I describe running a solution four times through a chromatography unit (in an instruction)? I'm translating a document from Russian: > The mean retention time for the first four injections of RNase should be (40.8± 2) min. If the mean RT is beyond this range, adjust the gradient system (change the content of acetonitrile within the 20% - 32% range) and **chromatograph** the RNase solution four times. I'm aware that we don't use **chromatograph** as a verb in English usually, but we do use it in Russian this way. What would be the generic English expression for this, usable in a procedure description? I know that we have the word **run** but this might be too colloquial for an official paper.

I would say simply:

> repeat the chromatography four times

or less formal, but quite acceptable:

> re-run the column (or whatever it is) four times

This puts the emphasis on the process.

But I’m not exactly sure what’s happening. You have four injections of RNAase. If they are not right are you repeating each once or what? If the former, then it would be:

> repeat the chromatography (or re-run the column) for each sample