Chromatography Forum

I have one Query about HPLC results
>
> I have a compound which i got analysed give
>results as follows i have doubt of manipulation
> Impurity RT area %
> 1 3.56 0.237
> 2 5.07 0.535
> 3 15.09 0.890
> 4 23.00 97.6
> and other small impurities peak
> I m Doing purification as follows
> 1. Ethyl acetate + Metanol
> 2. Methanol ( carbon treat ment)
> 3. Methanol slurry
> 4. Methanol Slurry
>
> After these four purification one by one still i m
>getting impurity at RT 3.56 around 0.20 by area % and
>purity incerase to 99.67 % at RT 23.00
>
> Now My question is is this HPLC results is look
>authentic.
> Why the impurity at 3.56 is not getting removed even
>after 4 purification in polar system
> while the impuritie at other RT getting less to
>almost less than 0.05(less polar compare to impurity
>at 3.56
>
> I welcome all comment
> if u need aditional info i will provide u to analyse
>theproblem
>
> Thanks
>
> Rajtush

I can think of many possible reasons (the most obvious is that the peak at 3.56 min is an artifact!).

What are your chromatographic conditions (column type, dimensions, flow rate, mobile phase, detection wavelength)?

In what is the sample dissolved?

If you change the mass injected (e.g. double), does the impurity % change?

In addition to what Tom has listed, one possible reason could be the degradation of the active and formation of said impurity during purification.

Check if the your compound is stable in the solvent used for purification??


JM