Chromatography Forum

Hello, all. I am hoping that a derivatization expert will see my post. I have a cis-diol compound, specifically 3-chloropropane-1,2-diol (3-MCPD, 3-monochloro propane diol).

The matrix is an aqueous biological medium with nutrients, buffers etc. I want to analyze by GC-MS, and I will need to derivatize.

My first thought was to make a phenylboronic acid derivative, (phenylboronate), but I am not limited to this option.

Does anyone have experience with making PBA derivatives, or can you suggest another option? I have pretty limited experience with derivatizations, and have had somewhat variable success with the techniques I have tried....

Can someone help me out?

Thanks,

Mike

If me, I would first try trimethylsilyl derivatization, we have used such with other diols.

I thought silyl reagents could not be used in water? Am I incorrect?
My matrix is aqueous, and it is a very polar compound, I don't think I can extract it to another solvent.

All depends on level. Like to dilute with pyridine or DMF, then one needs excess trimethylsilyl derivatizing agent to react with the water in the sample as well as the analyte.

Lots of the consumer products we assayed were in samples of 85% water. Guess what: thicker products don't necessarily contain "more stuff" - just more thickener!

I used to work for a company that made, among other things CMC thickeners..

Anyhow. So if I were to dilute 100ul or so of my sample in an excess of TMS reagent (500ul or so), I could react all the water and the remaining TMS would give me a good TMS derivative? I am thinking of the following: (Am I allowed to paste a link here?)

http://www.registech.com/chromatography ... hydrox-sil

We never calculated this, just did a brief experimentation layout to determine where additional BSFTA did not create more derivatized-analyte.

I'm not going to work out the math - I'm retired now - but for 0.25 gram samples of 80% water content diluted to 10 ml with DMF or pyridine, then a ratio of 2 parts sample solution above to 1 part BSTFA produced full derivatization. Yes, the vial may get warm from all the reaction heat.

Thanks for the help, sir. I am going to try this.

3-mcpd is my stock and trade. I do phenylboronic acid derivatization as do most people. It is very simple. Dissolve in water (you can scavenge junk with hexanes) add derivatizing solution, heat, cool, extract derivatives with hexanes and inject.

The other major method is HFBI which is a headache as the sample needs to be cleaned by a diatomaceous earth column, blown down, derivatized in an anhydrous solvent with a much less specific deriviatizing reagent, then cleaned after derivitization (usually water/hexanes as the water will kill the excess reagent that will kill the column) Then I had trouble with chromatographic interference but found db-1 gave the best resolution, db-5 had trouble resolving 2 and 3-mcpd.

Hi Mike


As CPG suggested Tri-sil BSA in pyridine in excess can overcome the water problem for silylation of your analyte for GC

Sometimes the reaction with water is slower than the reaction with the analyte

Regards

Ralph

I wish I saw this earlier but 3-mcpd is my stock and trade. My company makes HVP.

5g aqueous sample (2g dry =5g water or just 5g or some combination for pastes)
200ul 3-methoxy propane diol ITSD
1ml PBA acetone
90 deg 30 min
add ~2g NaCl and 2ml hexane.
inject hexane.