HPLC of Salicylic Acid Cream

[Marethyu]

Hi.

I am doing a school project and need some help on parameters used to conduct HPLC of salicylic acid cream. I have been able to find HPLC parameters for testing creams containing salicylic acid. However, the creams that are tested also contain other active ingredients besides salicylic acid. Are there any journal articles that detail steps on how to test a cream that contains only salicylic acid as the active ingredient with the parameters like the column used?

Thanks for the help in advance!

Edit: My lecturer wants us to find articles that detail how to conduct the HPLC on salicylic acid as he wants us to find the specific brands of HPLC machines and materials used. So he wants the brand of the column used etc.

Also, I have already read through the USP and BP and they only provide the HPLC parameters and do not provide information for the preparation of a sample of salicylic acid cream.

[HPLC chemist]

Don't worry about other active pharmaceutical ingredients (APIs). Your focus should be on the baseline separation (specificity, particularly of excipients) and your quantitation or recovery (100.0% is really nice!).

See ICH Q2(r1) for regulations.

[HPLC chemist]

Check the USP (United States Pharmacopiea) or EP (European Pharmacopiea) 1st. They may have a HPLC method that is appropriate in a monograph.

Don't become bogged down with HPLC methods or regulations that will only work for a raw material (drug substance). Look for monographs that apply only to Salicylic Acid in creams (a trip to the library). Eventually, you will want to prove any method you develop is more appropriate than a monograph method.

Remember, Salicylic Acid is a precursor or impurity of Acetylsalicylic Acid (ASA) or Aspirin, so maybe you can use that HPLC method too.

[HPLC chemist]

If I was a 'professor' my 1st question is whether the student 1st checked the pharmacopeias and the appropriate regulations (they are determined by where the cream is being sold). If the student didn't and went down a HPLC method development 'rabbit hole', I would give him/her a failing grade!

[Consumer Products Guy]

Need help?? This is a very easy assay. HPLC is UV detector and have acid in the mobile phase, C18 go from there. Yes, you should start with USP conditions because in this instance USP is fine.

My hint is: find a solvent which dissolves/disperses your sample cream and will dissolve the salicylic acid (I know from experience which solvent I would use). Note that your product likely contains a mix of salicylic acid and sodium salicylate, as pH would be too low for skin if all was as salicylic acid; so you might want to have a little acidity in your dissolution solvent. You will calculate as if all was present as salicylic acid because that's convention.