Dear all,
GC analysis revealed the presence of 7.62% methyle salicylate in the final formulation of my ointment, while the initial w/w of MS was 14%.
Where it has gone?? If it is because of hydrolysis, what is your solution in order to prevent this situation?
Thank you very much in advance.
This can be related to the temperature rise during the extraction process or the chromatographic condition of the analysis. Methyl salicylate is sensitive to the action of temperature, its t90, in ointments, at room temperature, is 120 days, and it becomes larger as it is kept under refrigeration. Could you use a cold and hplc extraction technique to carry out your study? I believe that if the problem is linked to temperature it can solve it, if not, an alternative (which I'm not sure is worth it) could be the derivatization of your compound for indirect determination by GC. Hope this helps. My regards!
Dear Mauricio
Thank you very much for your response. I will try this.
Please check your GC method parameters , sometimes the hydrolysis could be occurred from incubation and harsh conditions of gc parameter so try to use mild condition or use other instrument to quantify your compound
Dear Parham Akhlaghi thanks for sharing this interesting technical question with therRG members. In this context please have a look at the following potentially useful article which might help you in your analysis:
Stability determination of an alternative approach to use of liquid drug substance as oil phase in microemulsion formulations: Methyl salicylate
https://www.thaiscience.info/Journals/Article/TJPS/10988451.pdf
This paper has been published Open Access so that it is freely accessible as public full text on the internet (please see the attached pdf file). Also please check the literature references 34 and 35 in this article which refer to the hydrolysis of methyl salicylate:
Ref. 34: Effects of anionic micelles on the intramolecular general base-catalyzed hydrolysis of phenyl and methyl salicylates
Article Effects of anionic micelles on the intramolecular general ba...
and
Ref. 35: Effects of Cationic Micelles on Rates and Activation Parameters of Intramolecular General Base-Catalyzed Hydrolysis of Ionized Salicylate Esters
Article Effects of Cationic Micelles on Rates and Activation Paramet...
The corresponding authors of these papers can be contacted via RG so that you can request the full texts directly from on of them.
Good luck with your research and please stay safe and healthy!
Dear Frank!
Thank you very much. This is awesome! Gonna try this as well.
I'm impressed with everybody's approach and Frank what you provided was truly amazing :) Frank T. Edelmann . In Chess I would call you a grand master !!
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