problems in analysing clindamycin phosphate

[archie]

Hello friends..
I need some advice from all of you..please help me..

I have problems in analysing clindamycin phosphate in a cream.
I have tried some different method, but i always get same result. The analysis result always higher than it should be
( About 10% higher). I have injected the matriks (placebo) and it is not giving any absorbance. Do you have any idea where the 10% came from?

Thanks for your help.

[tom jupille]

Since you have placebo available, the obvious "fix" would be to always make up your standards in placebo. That way, any matrix effects would cancel out.

You should probably do that experiment (in effect, a "standard additions" run) in any case, and see how your slope and intercept compare to those when running pure standards. My guess is that the slope will be different, which might be explained by slight differences in peak shape due to the matrix changing the integration.