Bear in mind that, in theory, the ITHM cannot exceed the TFP; however, this does not factor in the variability involved in the sampling and analysis procedure. Since THM is typically measured by chromatography your experimental variability is no less than 10%, and probably more on the order of 15-30%. If your ITHM does not exceed your TFP by more than this you are probably looking at experimental error, which would tell you that your THMs form quickly.

Like to thank Mark for ur answer. Could you please elaborate the variability you are talking about in sampling and analysis, since m analyzing both the parameters in sample from same origin with same analytical conditions (EPA methodology on GC-ECD)