Chromatography Forum

Can anyone provide some insight on what methods have worked for the following residual solvent (467):

1) Analysis of ethylene glycol in sorbitol 70%

2) Analysis of formic acid in glacial acetic acid

Thanks
much

I've personally used a similar approach for both these analytes.

Fairly simple:

1. Transfer 250 - 500 mg of material into a 10 mL volumetric flask.

2. Dilute to volume in a compatable non-volatile solvent.

3. Inject sample

GC parameters:

1. Using ideal flow for the column and carrier gas (for a 0.53 x 30 m and He as the carrier, you would want to run around 2.6 mL/min) start the run off at 50C and hold for about 5 min. Slowly ramp ramp from 50C to about 150C at a rate of 5-10C/min. Ramp from 150C to near column max, or about 210C, at 20C/min and hold for two min.

Is there really any EG in 70% sorbitol?

Our supplier has stated that it is present.

We are using an Rtx-200 0.32 x 15 m 1 um.

The chrom parameter are as follows on Shm. direct inject.

2.5 psi head pressure
85 C initial for 2 minutes
ramp 5 /min to 115 C
then 30/ min to 310 hold

The issue is that the sorbitol is staying on the column and causing reproductbility issues.

Any suggestions to solve this?

There are good solutions for the formic acid which do not entail direct or split GC injection.

There are also reproducible methods for EG which also require a change in technique from your present setup.

If you care to discuss other options other than the present direction you prefer to follow I can discuss in more detail privately.

chromatographer1

Not too familiar with an rtx-200 column, but I would guess you are dealing with one of the more polar columns. Have you tried something less polar, such as a a DB-1 (or similar)? The decrease in polarity should let the sorbitol be released from the column more easily.

There are good solutions for the formic acid which do not entail direct or split GC injection.

There are also reproducible methods for EG which also require a change in technique from your present setup.

If you care to discuss other options other than the present direction you prefer to follow I can discuss in more detail privately.

chromatographer1

Hello
I am trying to analyze formic acid with the USP residual solvent method procedure C. I can't see the formic acid. I don't know also at what time it should elute. Can you help?
thanks

You will not be able to detect Formic acid using a flame ionization detector.

That is why you are not able to see it.

Using it in the presence of water will ionize the formic acid and you will not have complete recovery of the acid, but very poor recoveries.

The USP method is not suitable for this analyte as written.

I am a consultant. If you wish to contact me try chromatographer1 at aol.

best wishes,

Rod

For those of you who are following the subsequent branch of this thread (dealing with consultants), it's been moved to the "Around the Water Cooler" board:

http://www.sepsci.com/chromforum/viewtopic.php?t=9167