Chromatography Forum

Friends and Colleagues,

We must analise a corticosteroid ointment by HPLC-UV. Chromatographic separation is fantastic, but we have suffering a lot on improving the corticosteroid exctration from the ointment. During extration we have utilized the pair iso-Octane and aqueous phosphate buffer / MeOH solution. In true, the mixture aqueous phosphate buffer and MeOH is our mobile phase. All % recovery results were very bad: 97; 93; 89; 96; 95!
So, please, could you share with us your experience?

See, our Ointment Solubilities:
- Water: very low
- Phosphate buffer/MeOH: low
- MeOH: low
- DMF: low
- iso-Octane: moderate
- Hexane: moderate
- DMSO: moderate

See, our recent sample test preparation process
- Add the sample (1g) to a becker containing hot mobile phase: ointment melts in few minutes
- Transfer the mixture to a separator containing ico-Octane
- Extraction recovering the mobile phase
- Clean twice the ico-Octane

Any experience will be welcomed, considere that we are "in a jungle with a good rifle but with one unique bullet, and the fierce wolf comes toward us very angry".

Thank you so much,

Carlos de Souza Teixeira
teixeiracs@yahoo.com

I'm not so sure your recoveries are "very bad", looks to me like you're extracting most of the API, but not all. FDA ORA guidelines are 95.0 - 105.0 for finished products recovery.

How about freezing the sample and homogenizing in your organic solvent, then filtering?

Or homogenizing with solvent as-is? We'd try those two first.

Is your active stable to drying? If so, have you tried wighing the sample, then drying it, then extracting?

Dear C.P. Guy,

Thanks for your gentle replay. I made some possibilities and including hot water as separator solvent results went up 97.5% until 98.5%, so, I will add an Internal STD in order to up recovery results, since I am in the efficiency border, in the pertinent literature colleagues have published corticosteroid ointment recoveries about what your wrote.

Let's see what Chemistry deserves to me today.

Any case, all the best for you.

Warm hugs from Brazil,

Carlos de Souza Teixeira
teixeiracs@yahoo.com