Assay of Benzoyl Peroxide and Clindamycin Phosphate

[karlhaw]

Hello, I am currently working on a acne gel which contains Benzoyl Peroxide and Clindamycin Phosphate as active ingredients. I am looking for one procedure to identify the compositions of both of these compounds together. Thank you in advance.

[Consumer Products Guy]

We've assayed for benzoyl peroxide but not the other. Benzoyl peroxide was very straightforward, the toughest part is getting and making a good standard, like the standard has significant water so the level of BP must be determined by titration at the time of making the standard solution for HPLC.

[Vlad Orlovsky]

We have a method for both on Primesep 100 column. Aminosugar is retained by cation-exchange mechanism and benzoyl peroxide by RP mechanism.
Something like these:
http://www.sielc.com/Compound-Amino-Sugar.html
http://www.sielc.com/Compound-Benzonitrile.html

You might need ELSD, RI or LC/Ms for amino sugar

[karlhaw]

Hello guys and thanks for the reply. Consumer products guy can you please elaborate on the assay you've used on benzoyl peroxide. And Vlad, we do not have that kind of equipment in here. We only have a standard spectrophotometer and a standard HPLC.

[Consumer Products Guy]

We used standard HPLC and column. Note that we only did this once, but results were straightforward, and BP peak sharp.

We had looked at the USP assay then, USP used 254 nm so we knew it had been developed back when detectors were 254 nm only. And it screamed for modernization.

So we used product made in house at 10% BP level and placebo product
BP standard from Sigma Aldrich, about 8 e-4 grams/ml in ACN
Samples were 1.2 grams in 100 ml ACN

150mm x 3mm 3µ RP-18 column (Type B)
75% ACN, 25% of acetic acid in water (0.4% acetic acid) isocratic
flow=0.50 ml/min 280 nm

BP nice peak at about 6 to 7 minutes, no peak there in placebo product

[Vlad Orlovsky]

I expect clindamycin to be visible at 200-210 nm due to carbonyl and sulfur.