Chromatography Forum

With very little success, I have endeavored to extract and quant L-Menthol via GC FiD.
The analyte is extracted from a dense creme formulationt that is comprised of waxes, stearyls alcohols, vitamins, fragrances, and glycerins. The chromatography, which I will post as soon as I can get it loaded onto tiny pic, has numerous small regularly occuring little peaks spaced about 30 secs apart from the major peak at 6 mins (which compared to the un-extracted STD sol'n peak also at 6.032 mins.). Why is chrom so decorated with these regular little peaks--which appear even in the un-ext'd STD? I tried to syringe filter via Acrodisk but no success. Is the L-isomer isomerizing? I have not yet ventured to determine if the peaks interfere with quantiation as at this juncture I am at the qualitative i.d. stage of method development. Extraction solvent is dichlormethane. In terms of my sample prep, 1 gram of the ointment cream is disperesd in warm water, then extracted with methylene chloride, then I take this bottom layer and dry over anhydr sod sulf..
Any ideas appreciated from the brain-trust.

Here's how we assay for menthol in personal care products:

We extract the sample with DMF, and filter (disposable HPLC sample filter). We also make up the menthol standard in DMF. We then mix same volume of sample or standard with BSTFA derivatizing agent in an autosampler vial, then cap and mix. We get one peak for menthol. We use DB-5 type capillary, but I'd stay with what you are using.

Dear Consum Prods Guy:

Are you saying that your method calls for a post-extraction derivitization step?
I am also using the 5% phenyl column (30 m x 0.25 film). I am surprised that you have not observed the numerous small peaks that tend to decorate the chrom as I have observed.

Dear Consum Prods Guy:

Are you saying that your method calls for a post-extraction derivitization step?

Yes, very common in our lab. Just add the BSTFA to the DMF extract, shake, and inject.

I am also using the 5% phenyl column (30 m x 0.25 film). I am surprised that you have not observed the numerous small peaks that tend to decorate the chrom as I have observed.

Actually, I'm running standared and samples overnight, just by happenstance. I haven't observed any other peaks from the menthol, but I never tried to assay for menthol without the derivatization, as we typically derivatize stuff like propylene glycol, glycerin, etc., that makes the menthol more stable in the inlet. Of course in our finished product we do see other peaks from matrix components.

If you post your E-mail address, I can E-mail to you sample chromatograms.

Jumpshooter,

I set up a method for a customer to do this and Camphor at the same time. Don't have the method in front of me but I will see if I can dig it up easily. Depends a lot on how much Menthol you are analyzing for since it involved a relatively large dilution factor. Was for Menthol and Camphor in a hand cream by the way....

I'll see what I can find when I am back in the office.

Best regards,

AICMM

Jumpshooter,

Dissolve hand goo in lots of water. Add IS to water. Aliquot sample of water into separate vial, add equal amount of hexane and shake. Pull off hexane and put in a vial. Sample is now ready for analysis. Analysis on a wax type column rather than non-polar column, aided by the fact that that GC only does Camphor and Menthol analysis.

Best regards,

AICMM