How much is too much?

Abstract

Several guidelines help address the question of how much sample can be injected onto an LC column. Too large a sample mass will overload the column, causing peak distortion and shorter retention times. Some of these same effects can be observed if too much of too strong a solvent is injected. It is best to stay on the safe side and be conservative with the mass, volume and injection-solvent strength used for routine methods. Sometimes overload is unavoidable, especially if one analyte is at high levels and another is at trace levels. One way around this problem is to make two injections, a small one for the parent drug and a large one for the trace components. Whatever choice is made regarding the injection solvent and sample size, it is wise to determine that the selected conditions are stable by finding out what happens if the injection size is increased.