Chromatography Forum

Hi all, this is my first time on the forum. I've been lurking around here and there reading threads and the community seems great!

I've been doing searches online and reading through papers trying to find some help in developing a QC method for analyzing dimethicone in a lotion. I've come across AA as the best means of analyzing because it is matrix independent, but I don't have access to the instrument. I've been trying unsuccessfully using IR with methylene chloride as a solvent and lowering the pH to 3.0 to bring down the viscosity to help extraction. Every step forward seems to bring about new problems. I'd really like to get the IR method working but I'm so frustrated, that I'm looking towards other options. I've read some articles and threads here about using HPLC with an ELSD, but they all seem to be pretty involved as far as a QC method goes. Are there any articles methods out there for HPLC that are relatively "quick-and-easy" as far as an HPLC analysis goes?

I've assayed dimethicones by FTIR after chloroform extraction, using a liquid cell.

But as an active, good luck on achieving accuracy and precision requirements, and to demonstrate such assay is stability-indicating.

AA or ICP for total Si works as a QC tool.

I've looked at a variety of silicones via HPLC (RI, low UV, and ELS) and if you're going to do it this way, you'll need to come up with and validate your own method because it will need to be specific to your particular matrix. I was looking at D3-5, I believe - it was a LONG time ago - and if I recall correctly, I had relatively good luck with using a C8. Dimethicones are complex mixtures, as I'm sure you're aware, and the potential for frustration may be quite high here.

With that said, I did just dig thru some archives I have and found an old ELS application from Alltech for dimethicones. Drop a note at christopher-dot-judd-at=BASF-dot-com if you'd like it.

Cheers!