Chromatography Forum

Hi i have a question regarding the blank injection for HPLC SEC.
Some guidelines prescribe to use a blank at the beginning to see if there is a stable baseline and no unusual peaks. From what limit can you say there is an unusual peak? is there quantification described in the USP or Ph. Eur. or some other guideline?

All help is welcome, thank you in advance

I am unaware of any "limits" in any guidelines as injecting a true blank at the start of any method (note: a "true" blank = the mobile phase at initial conditions) is part of following good chromatography fundamentals. Blanks should be included in all methods, esp quant, but all methods. The "blank" injection demonstrates that the mobile phase and injection solution are the same, with almost no measurable "peak" observed on the baseline (the 'peak' will of course depend on the type of detector used and configuration, which must be defined). *By UV, you should still see a small peak which corresponds to the Tzero time from the change in pressure caused by the make/break of the injection valve (normal). No other peaks should be visible.