Chromatography Forum

Dear All,

I am doing analysis for 2-Ethyl Hexanoic Acid by GC as BP 2009/EP 7.0. Now the problem for me is the calculation part. In EP/BP the calculation part is given as

{Area ratio of sample/area ratio of standard x weight of standard / weight of sample} x 2

sample preparation: 0.3g in 1 ml internal std + 4 ml conc. Hcl.

standard preparation: 0.075g 2-eha in 50ml Internal std. 1 ml from this solution + 4ml conc.Hcl.


Now my question is what is the role of "2" in the calculation part

Plz explain.........


Regards
Mohammad.

Mohammed:
Typically, at the end of the calculation one should mutiply by the "concentration of the STD". Evidently that "2" must represent a STD concentration. However, in this case it seems that Mysterious "2" is a fudge factor that whomever derived the formula used to make their results "look better". No one knows what that "2" means--it is unit-less. Evidently it was thrown in to correct for consistently observed differences between the recovery of the Analyte in the test Sample matrix versus the Analyte recovery observed in an un-extracted STD. Ostensibly, the extraction efficiency from the real test sample in that Test Method is only 50% that observed in the un-extracted STD. Hence, to compensate one must multiply the final result by 2x in order to normalize to a "100% extraction efficiency"--as observed in the un-extracted STD. Sometimes researchers use such "fudge factors" to compensate for poor recovery when quite honestly more "method development" work is needed to make the assay work. Ah salamm a lakim!

Thanx for the kind briefing....... now its clear for me.

W/Salam

Regards
Mohammad.