Chromatography Forum

HI everyone, I have a problem of passing the assay testing for Salicylic acid RM usp grades (spec: 99.5 - 101.5 %)

I am using my HPLC method instead of USP titration method.

method method is work fine for my products (acne treatment), but I guess my products are broader spec. than the RM (USP)

we have this method is validated for our products. and the placebo effect was also performed so, i thought the method should be oK for the raw material.

method: column synergi hydro-RP
column temp: 40C
1.0 ml/min
inj: 10uL

I just looked at USP 37 Official Monograph for salicylic acid two minutes ago:

The range is 99.5 - 101.0 % on the dried basis, not 99.5 - 101.5 %

The assay listed is titration with base, the only HPLC assay is for Related Compounds.


Recommendation: do the titration assay, won't have to purchase USP reference standard salicylic acid at their pricing.

Questions: are you a receiving facility that buys USP salicylic acid? If so, do you run ALL the USP Monograph listed tests?

Or are receiving facilities (or just the suppliers) required to run ALL the USP tests? Yes, more of a compliance/cGMP question.

Yes, 99.5 - 101.1%
I don't want to test by titration method because my drug product we already use validated HPLC method to test. Maybe there is error on weighing technique . Or Salicylic acid absorb moisture during weighing or something. I saw the weigh also change during weighing. I also try weigh by difference, weigh direct into flask. Any other technique that u can recommend ? Thx

Dry the product before weighing using the loss on drying procedure, keep in desiccator.

Or correct for percent as dry basis by running companion sample.

I still recommend titration for this, free up your HPLC or use HPLC for the finished goods testing.