How Calculate Total impuriteis?

[Parham]

Hi everybody,
I wanna calculate total impuriteis of cefixime,
I plus total impurity before main peak and devided by area of main [cefixime] peak,
in pharmacopoeia method not mentioned about peaks after cefixime peak and if i plus area of peaks that exist after cefixime peak my API is reject.
Should i plus peaks after cefixime peak?
Thank you so much.

[Juan2011]

Hi Chegini,
First of all, I would like to know the method you are using to calculate the impurity. Is it area percent or response factor?

[paulw]

Many compendial methods have a requirement such as 'gather data for no less than twice the retention time of the API'. Others can have even longer run times if a known impurity elutes later. Given that, I don't think it wise to just ignore peaks because they are retained longer than your API.

[DSP007]

Hello
c BP2007

Related substances

Examine by liquid chromatography (2.2.29) as described under Assay. Inject reference solution (b). Adjust the sensitivity of the system so that the height of the principal peak in the chromatogram obtained is at least 50 per cent of the full scale of the recorder. Inject the test solution and continue the chromatography for 3 times the retention time of the principal peak. In the chromatogram obtained with the test solution: the area of any peak, apart from the principal peak, is not greater than half the area of the principal peak in the chromatogram obtained with reference solution (b) (0.5 per cent); the sum of the areas of all the peaks, apart from the principal peak, is not greater than 3 times the area of the principal peak in the chromatogram obtained with reference solution (b) (3 per cent). Disregard any peak with an area less than 0.1 times that of the principal peak in the chromatogram obtained with reference solution (b). Full prescription
Also need use placebo ( blank solution) probe , and not calculated blank peak.Our girls sometimes forget to do it and get an "amazing number"