Chromatography Forum

Hi there,

newbe here, we intend to analyze the common oxygenate such as methanol, ethanol, ether, DME etc from MTBE. To complicate the matter further there are C2,C3 up to C6 present in the matrix. I'm thinking of the following configuration basically col1, DB-1 (25m*0.53m) to strip the HC, Col2 Rtx-1(60m*0.53) to isolate the MTBE from the component of interest and col3 GS-oxyplot(10m*0.53) as an analytical column to separate all the oxygenate.

Question will this one work?
Is there another easier/faster route?
Cost is a secondary factor here.

Plumbing diagram is attached below, just click to enlarge.



Thanks in advance for any help.

Rgds
KAE

kae,

First off, using your current scheme, you never put the oxyplot in line with the 60 meter column so there is no way to transfer analytes to the oxyplot. Second, neat MTBE? So you are measuring impurities in MTBE product? Are you going to throw out the MTBE, you don't care about measuring that with this scheme? Third, you are using a loop injector which typically means gas phase constituents. Are you really shooting a gas phase stream or are you injecting a liquid? Finally, did you list all of the oxygenates?

Best regards.

A petrocol DH150 from Supelco will separate methanol from isobutane with a starting oven temp of 60C. This will also give good separation for DME and MTBE. Not sure about ethanol but I think so.

I forgot to qualify that. It depends on the concentrations of methanol and isobutane. Methanol elutes before isobutane at this temperature.

seems like you are overcomplicating it. You're going to have to have precise switching to get it just right. It seems like this is a job for a custom column from Restek or J&W (Agilent)

I'm not sure, but maybe a simpler approach would work. Short length of DB1 set up as a stripper column with valve, followed by the OXYPlot.

The OXYplot won't retain the light hydrocarbons enough to matter, so you could use the OXY column alone if that's all you were worried about.

The MTBE complicates it. I'm thinking the MTBE has a high enough BP compared to the lighter oxygenates that you can strip it out using the DB1 column.

So the light HC and light oxygenates fly through the DB1 to the OXY. The MTBE is trapped and backflushed from the stripper column. The light HC's aren't retained long enough on the OXY to interfere with anything.

Would ASTM D5441 fit your needs?