Fraction collection dilution

[KarenJ]

Hi,

I am going to be performing a separation on a sample and collecting the fraction containing the peak that we are interested in. I have been asked to then dry the sample down and reconstitute at the original concentration. The peak is a completely unknown molecule and I have no idea what concentration is in my original sample. Is the dilution factor simply my injection volume divided by the volume of eluent that I collect or are there other factors that I need to take into account? If this is the case, I could then dry the same down and reconstitute to the injection volume.

Thanks,

Karen

[MK]

yes, if your recovery is 100%. I think, in practise you won't get 100%. You should be able to determine this by reinjecting the collected fraction followed by comparison to original peak.

[JA]

Why does the collected material need to be reinjected at an identical concentration to the original sample? My guess is that your calculation is only applicable if you inject a pure compound and collect it with 100% recovery. When does this kind of thing happen?

How about reducing both your crude sample and collected fractions to dryness and make up your own, known, concentration.