Analysis of analgesic cream

[redzilla]

Hi everyone,

I have been given the task of developing a method to assay capsaicin, methyl salicylate and menthol in a topical cream. Does anyone have any experience with any of these components using HPLC? I am pretty sure I won't be able to do the menthol (traditionally by GC I believe). Before anyone suggests it...I only have the HPLC to work with, no GC.

I would prefer to perform the capsaicin and methyl salicylate in one method, but if it requires two separate methods, that is ok. I have a general idea for the capsaicin, as I will be trying out the USP method for the raw material. But if anyone has anything to contribute that might help my process along a little faster, I would greatly appreciate it!

Thanks!

[oscarBAL]

Hello redzilla, i think I really can't help you, in fact I am interested about that, one time i had the same task, before left my last work. I don't remember the chromatographic conditions but I Know that you can find it on AOAC or in the Altech catalog, the methyl salicilate and the menthol are very easy by GC, and the capsaicin by HPLC as well, but the real problem is that you have a CREAM!, and it will be very dificult to break the amultion, by other side you have to be sure that realy is a cream and not a cream-gel, with a carbopol base, remenber that you have substances that make dificult a cuantitative extraction of your analyte, probaly you will need two extraction method, and do estandar adition too! as I said you I know is not a big help, any way good luck!
SPE coul be and option but I am not realy sure

[Mark Tracy]

I have a simple extraction for skin creams. I developed it for pulling out hydrocortisone, and it also gets the parabens. I think this has a good chance of working on your compounds since they are of similar polarities.

Disperse 0.5 g of cream into 7 mL of 3A denatured ethanol, sonicate if needed. Dissolve in 1 mL of hexane (or heptane if you prefer). Add 3 mL of water and separate the phases. Filter and shoot the EtOH layer. You may need to tune up the water to ethanol ratio for best results with your sample. Other people in our lab have used this method for various things like antifungal spray.

[redzilla]

I'm not so concerned with extracting the analytes as I am with establishing the HPLC conditions. I work with sunscreens/creams on a daily basis, and most analytes are easily extracted with methanol and/or THF. But thanks for the input! I'm looking more to see what my conditions should be (wavelength, mobile phases, etc.). Thanks

[JasonC]

Hi Redzilla,

I have an HPLC method on Luna Phenyl-Hexyl as follows for methyl salicylate and menthol on one method. You may be able to get capsaicin in there as well? I work for Phenomenex as a technical support representative in San Diego. I noticed a recent post of yours with overlapping peaks and I would like to offer to help you out with that issue as well. Please feel free to contact me and I can help take care of that (perhaps replace column with this one below?).

Method details for methyl salicylate and menthol:

SAMPLE ANALYTES:
1 Methyl salicylate
2 Eucalyptol
3 Menthol
4 Thymol

Column: Luna 3 µm C6H5 / Phenyl Hexyl
Order No: 00F-4256-B0
Dimensions:150 x 2 mm ID
Flow Rate: 0.7 mL/min
Temperature:60 °C

Eluent A: 0.15% TFA in Water
Eluent B: Acetonitrile
Pct. A: 63
Pct. B: 37
Elution Type: Isocratic

Best regards,

Jason

jasonc@phenomenex.com