Does anyone have a method-wet, chromatographic, etc. for the analysis of high levels (20-30%) of Glycerol (Glycerine) in skin creams? I have started developing a GC method, but thought someone might already have a wet method developed.

Thanks in advance.

If you want a wet test method, there is Official Method number Da 23-56 of the American Oil Chemists Association (AOCS) which is a titration with standardized thiosulfate after reaction of the glycerine with excess periodic acid. However, this is time-consuming, and a certain excess of reagent must be present for this to work properly, sometimes requiring re-do from middle step. And other glycols such as propylene glycol, sugars, and sugar alcohols such as sorbitol will absolutely interfere. I published a GC method in the Journal of the AOCS in 1987 which works in the presence of these materials and is very amenable to automated GC operation, that's what the Dial Soap Corporation uses to this day: "Quantitative Determination of Glycerin in Soap by Capillary Gas Chromatography", JAOCS, Vol. 64, No. 9 (September 1987), pp. 1356-1357. K. Molever.

K. Molever, thank you very much for providing me with the reference for the GC method. I ordered it today, and will try it as soon as I receive it.

Thanks Again!

Most likely most types of nonpolar and slightly polar phases such as HP-1 or HP-5 or their counterparts will work fine. You'll just need to dilute your samples more and make comparable concentration samples so you don't overload the GC column or detector. If you want to use internal standard quantitation instead, a good internal standard for assay of both propylene glycol and glycerine is butanediol (butylene glycol).

K. Molever, I received the reference today. I think I will try running it on a DB-5, 30m x 0.32mm, 05 u df. I was curious if it was necessary to derivatize the sample first with the BSTFA, or if it is possible to just dilute and shoot without derivatization? Did you try your method without first derivatizing, and if so what were the results?

We tried glycerine underivatized also, back in 1982, but peaks tailed, and the derivatized glycerine assay was so easy in bar soaps and liquid soaps. Remember, this was developed when fused silica capillary columns were "newbies". However, with new USP 25 glycerine raw material testing required, our facility also had to set up to do the new assays on glycerine itself, underivatized, and this may work fine on your product. Gas chromatograph with FID (e.g. Agilent Technologies 5890 or 6890 system) and automatic sampler, fitted with a 30 m x 0.53 mm i.d. SPB-624 capillary column (Supelco #25430). The inlet liner must be of an inverted cup type (Restek #20990 mini-Lam split liner) or a spiral type (Restek #20706 cyclosplitter). Helium carrier gas linear velocity * 38 cm/sec. (this works out to a carrier gas flow of about 5 ml/min.,
and a capillary head pressure of about 4 psi.). The split ratio should be about 10:1 (split flow * 50 ml/min.).
Inlet Temp. = 220 °C FID Temp. = 250 °C Initial Temp. = 100 °C Initial time = 0 min. Oven rate = 7.5 °C/min. Final temp. = 220 °C Final time = 4.0 min.
Caution: maximum column temperature is 230 °C Suggest glycerine standard solution in range of 0.5 to 10 mg/ml I'll try to attach a chromatogram of underivatized glycerine, if it doesn't work, E-mail me. The peak just before 7.0 minutes in diethylene glycol, the peak at about 7.5 minutes in glycerine, using conditions above, underivatized.

We tried glycerine underivatized also, back in 1982, but peaks tailed, and the derivatized glycerine assay was so easy in bar soaps and liquid soaps. Remember, this was developed when fused silica capillary columns were "newbies". However, with new USP 25 glycerine raw material testing required, our facility also had to set up to do the new assays on glycerine itself, underivatized, and this may work fine on your product. Gas chromatograph with FID (e.g. Agilent Technologies 5890 or 6890 system) and automatic sampler, fitted with a 30 m x 0.53 mm i.d. SPB-624 capillary column (Supelco #25430). The inlet liner must be of an inverted cup type (Restek #20990 mini-Lam split liner) or a spiral type (Restek #20706 cyclosplitter). Helium carrier gas linear velocity * 38 cm/sec. (this works out to a carrier gas flow of about 5 ml/min.,
and a capillary head pressure of about 4 psi.). The split ratio should be about 10:1 (split flow * 50 ml/min.).
Inlet Temp. = 220 °C FID Temp. = 250 °C Initial Temp. = 100 °C Initial time = 0 min. Oven rate = 7.5 °C/min. Final temp. = 220 °C Final time = 4.0 min.
Caution: maximum column temperature is 230 °C Suggest glycerine standard solution in range of 0.5 to 10 mg/ml I'll try to attach a chromatogram of underivatized glycerine, if it doesn't work, E-mail me. The peak just before 7.0 minutes in diethylene glycol, the peak at about 7.5 minutes in glycerine, using conditions above, underivatized.

1.cdf 1.cdf (26 k)

This can be very easily using HPLC on a Bio-Rad HPX 87H (or equivalent) using 0.001mm H2S04 mobile phase.

Molever,

Thanks once again for your advice. I ordered a MTX-624 column today, and will try the analysis next week. I'll let you know how I make out.

I just did a very similar analysis last week using a 250mm amino column, an isocratic acetonitrile based mobile phase (ca 90% MeCN), and an RI detector - worked like a charm, eluting glycerine in a sharp, clean peak at about 10 min. Do note, however, that I developed it on a spur of the moment, as it was an emergency request (ie, "See what you can do with this in 24 hours or less..."), so please don't think that I have a fully validated method.

I would be very careful in cleaning up your sample if you're using ion exclusion, as you don't want all of the nasty organics to foul the column. Reversed phase SPE should do well for that. FWIW, no clean-up appeared to be needed with the NP method. It was a dilute in MP and shoot afair with no nasty side effects that I could see.

Good luck.

Chris

Greetings. We have an old waters column for triglyceride analysis given to us but we don't have any idea how to use it. The leaflet is not included in the box and we tried looking for info from different sources with not much luck. The column specs: Waters HPLC column Part no. 84346. Thank you and more power to your forum.

How about asking Waters?