Determination of ethylene glycol

[Pegry]

Hi everybody,

we have to analyze the residual ethylene glycol in a pharmaceutical product. We have access to headspace sampler and to liquid sampler..
Do you have some experience in the analysis of ethylene glycol? I think I'm going to use liquid injection after dissolution of the product because ethylene glycol has a high boiling point.. Do you have some experience or clues on this type of analysis??

Thanks in advance for the answer,

best regards

Davide

[chromatographer1]

I have done this by GC and by LC in pharmaceutical products.

It is far easier to do this by LC using a refractive index detector assuming you are looking for amounts >100 ppm.

Of course, your matrix may not be good for the isocratic conditions needed.

If you have multidimensional LC available it would be highly advantageous, switching your precolumn to vent after the EG leaves the precolumn and continues on a suitable column to the RI detector while your matrix elutes to vent.

Ultimately, doing EG is difficult unless you derivatize and that can open a large can of worms.

Perhaps, someone else will have better advice.

best wishes,

Rod

[Consumer Products Guy]

I've done ethylene glycol and similar by GC. If you want to pursue the underivatized route, why not try the capillary listed for related substances in glycerin in the USP? If ou want to dissolve in DMF and derivatize with BSTFA, be aware that derivatized ethylene glycol will elute just after the derivatizing agent (non-polar capillary).

[Pegry]

First of all, thanks everybody for the answers..
I've made some tries solubilizing my product in MeOH and analysing the ethylene glycol underivatized in a RTX-624 column.. The problem is that I can solubilize only 1mg/mL of my product in MeOH so I want to change the solvent to to solubilize more product (10mg/mL) and hence have more sensibility. I have found that my products is freely soluble in water and in DMF..
Now I want to ask if, on you experience, is better to use water or DMF in the analysis of ethylene glycol. I'm speaking about the peak shape of the glycol and the column stability to DMF and/or water..
Which one would be better to use?

Thanks in advance for the response..

Have a good day,

Davide

[chromatographer1]

Your question is a tough one. (Notice the absence of posts answering it.)

Water is not good for any silicone based column, but your peak with EG is likely to be better if water is the solvent rather than DMF. I won't claim that it will not be possible to use DMF, you may very well with the right conditions be pleased with the results, but a basic surface for the column will not improve the EG peak.

I tried another silicone based phase capillary column some years ago to measure EG and Propylene glycol in water and was pleased with the results ................. for about 6 injections of my standard............ then peak shape degraded quickly to unacceptable. It was with a competitor's column so I won't mention them or the type of phase.

I think it is a decision based on the durability of the column being injected with water versus the recovery of the EG using DMF.

I suspect you will have to try it and see.

best wishes,

Rod

[Earl]

If getting a new column is an option then I recomend getting an SPB-1000 PEG phase column from supelco. This column works well for glycols and water can be used as the solvent. (a stabilwax from restek should work as well)

[Earl]

If getting a new column is an option then I recomend getting an SPB-1000 PEG phase column from supelco. This column works well for glycols and water can be used as the solvent. (a stabilwax from restek should work as well)

[Pegry]

Hi everybody,
thanks for the answers.. At the end, I've don the job using the RTX-624 and dissolving the product in MeOH. I've tried with water and DMF but the sensitivity and the peak shape was bad than with MeOH. With the GCMS in SIM mode I have reached a S/N of about 10 injecting 50pg/uL. I have dissolved 50mg of sample in 50mL of MeOH and injected 1uL into the GCMS..
Thanks again for the answers,
Have a good day,
Davide

[chromatographer1]

Thank you for telling us the end of the story.

Many folks don't have the proper manners that you possess.

best wishes,

Rod

[Consumer Products Guy]

Always remember, when injecting water that it expands a ton in the inlet when vaporized, so keep your injection volumes low (like 0.5 ul).