Chromatography Forum

Hi

I Have at problem with my analysis of triglycerides. Currently I am using a Split/Splitless inlet at 350 C in splitless mode, but my samples are not showing my glycerides. The samples are fat treated with BSTFA, dissolved in heptane.

If i run a Std. solution of BSTFA treated glycerides I have no problem seeing the glycerides, but if the rest of the matrix is present the glycerides disappear. From this I conclude that something in my matrix reacts with my TMS ethers, probably in the hot inlet.

I have read a few papers on the subject that states a on column injection should be used. Therefore I am thinking about buying a Cool On-Column inlet for my GC.

Agilent quotes my a price around 6000$ for a new COC inlet with EPC valves. This is to much for me, so I am thinking about going another way. I have found a used COC inlet for sale on the net, but this inlet is without EPC valves.


Could I install a COC inlet with my current EPC valves for my Split/Splitless inlet, and get Chemstation to accept the new inlet as a COC inlet with EPC valves?

Could I run the COC inlet without EPC valves and set the pressure manually? And what valves would I need to do this?

An overview of the plumbing in the GC can be seen in the "Advanced User Guide" for a 7890 on page 154 (S/SL) and page 222 (COC) here. http://www.chem.agilent.com/Library/use ... -90015.pdf


Best regards
Forse

This will not work. The 6890 takes the information from the EPC module to tell it what type of inlet that you have. Therefore the 6890 and the ChemStation would both think that you have a standard split/splitless injection port installed. Also, the Cool On Column does not have a split vent, so this would also be a problem if you tried to use the split/splitless EPC module.

Both the ASTM and EN methods used for this analysis call out a Cool On Column injection port.

Gasman

This seems like a lot of money! You might be able to buy a secondhand instrument for less than that!

GCguy

This will not work. The 6890 takes the information from the EPC module to tell it what type of inlet that you have. Therefore the 6890 and the ChemStation would both think that you have a standard split/splitless injection port installed. Also, the Cool On Column does not have a split vent, so this would also be a problem if you tried to use the split/splitless EPC module.

Ok. When the computer gets the information from the EPC module it is no good. I think I would have been able to work around the other problems.

This seems like a lot of money! You might be able to buy a secondhand instrument for less than that!

Yes, but I cant find a used system with a COC inlet, so I dont have a lot of options.
I think I will just have to bite the bullet and get a new inlet.

http://www.srigc.com/2005catalog/cat33.htm

close enough?

Before you go and purchase equipment, you could revisit the derivatization reaction... How exactly are you preparing your samples? What is the composition of "the rest of the matrix?"

Kerri