Pentane solvent Injection Issue

[Peter Apps]

I was thinking that there must be a badly directed flow of hot air from an oven vent or something - I am pretty sure that a room temp of 36C violates regulations about working conditions for humans, never mind instruments !

The chilled samples and syringe works well for manual injections, but I thought that modern chromatography was all done automatically

Peter

[Don_Hilton]

Having used CS2 in a mass spec - because of the character of unrefined petroleum, you can use CS2 in a mass spec. For the particular crude I was looking at, it was the only solution. Which gets me to the point. You work with what it takes to get the job done. If CS2 is not suitable for your application, then leave it alone. If it is the solution for you, cover your nose and go for it. (Actually make sure there is good ventilation!) And while CS2 is dirty stuff, different vendors may have different mixtures of dirt (excuse me – impurities) – making one brand better for your work.

Personally, in the problem mentioned above my preferred solution is to keep the samples, syringe, and perhaps the operator at a cooler temperature. The separation of a solvent that boils higher than pentane and will separate from hexane can be tricky. The other way to go is to use a solvent that boils higher than all the components of interest. This gets messy because you tend to have a reverse solvent effect – broadening all the peaks that come out before the solvent peak. But, in desperation, if it works for you…

[dblux_]

... The other way to go is to use a solvent that boils higher than all the components of interest. This gets messy because you tend to have a reverse solvent effect – broadening all the peaks that come out before the solvent peak. But, in desperation, if it works for you…

In this specific case when the author wants to determine hydrocarbons from C6 to C36 (!) using higher boiling solvent is (IMHO) not a good idea.
Due to the nature of analytes I would probably personally choose CS2.

But let's be honest. Nearly two weeks passed and we still don't know the temperature in his/her lab. Air conditioning system was mentioned. It should be repaired. And a fan in autosampler tower should be checked (if applicable in specific instrument). From my experience temperatures up to 29 degC won't make pentane to flow from the syringe (needle gauge 26s).

[MSCHemist]

How about carbon tet? With no C-H bonds it probably has a very low response on the FID so although there might be a peak it might not interfere with anything.

[AICMM]

Regarding CT, there are lots of reasons not to even consider this, no offense MSCHemist. 1) It will, interestingly enough, respond, although poorly, just like CS2. 2) It will be murder on your FID parts. 3) It is a known carcinogen (this probably should be first.) 4) It will be bloody hard to get a hold of, especially at the volume of TNRCC extractions, and even harder to get rid of.

I am still interested to know if he can chill the tray. Most of the AS's I have seen have the means to hook up a circulating coolant stream.

Best regards,

AICMM

[Darraghcls]

Apologies for the long delay in replying, I was enjoying some annual leave that was more than needed.

Thanks for the advice,

I'm going to try running using CS2 and see what happens. Though with the sample numbers that may be required I don't think it will be runner purely on H+S grounds. And I might be able to get my hands on a chilled tray for our AS.

We don't have air-con in the lab and its only recently I was allowed drill holes in the wall to vent the GC's outside, even still the lab is constantly 25oC or so and up to 30oC if its any way sunny out (37oC is our record during a particularly hot summer).

I've explained to my boss that the lab is abit on the hot side for this method to work properly, who knows maybe it will force him to install air-con in the future.