Chromatography Forum

It's best to choose a highly volatile solvent. The solvent needs to "flash" in the injection port and also precede your analytes through the column so as not to interfere with the resolution of your analytes. That's why I recommended DCM. Essential oils should be miscible in DCM and DCM is very volatile and less likely to be retained by your stationary phase.

I agree with Peter that 10 meters is a very short column if you are looking for resolution of all of your components.

Do you know the stationary phase of the column?

Hi Don,

Now i've got my GC delivered. It has 2 FID's and two columns (cat no. 6172 25m 0,25mm 0,2um) but one coulmn is broken about 10cm from the connection to FID.



Now i'm wondering if i should buy a longer column or it has to be the same type and length?

Cheers!!
/Alvin

I wouldn't worry about 10 cm. It is very insignificant compared to 25 meters. According to the catalog, this column has a max temperature of 225 degrees. Please don't exceed this. As Peter suggests, use only 1 column until you become proficient. Avoid allowing air to enter the column. When you attach it to your carrier gas, allow plenty of purge time to remove oxygen prior to ramping the oven.

I have never use a cyanopropyl phase for this type of work. Please keep us posted.

The 0.25mm internal diameter will give great separation with the short length but will also reduce the max analyte loading you can get by with. You should be able to dilute quite a bit or use a high split ratio and still get good sensitivity.

Thank all of you for all tips and for your kindness!!

Peter: There are two separate inlets and the both columns are exactly the same type. (well the one is about 20cm shorter than the other =P )

Don: Yes i will, it seems that there are two parallel systems. I have a lot of other things to fix until i will start to run it. First i need to install my old XP PC, i just purchased an old 10MB coaxial ethernet PCI card for it.

I am also giong to change all the copper lines for air, N2 and H2 to plastic pressure lines. N2 i have already but i miss a compressor with filter and H2.

Cheers!!
/Alvin

Do not change the copper lines for plastic - the plastic will bleed volatile organics into your gasses, giving you a high and unstable baseline, and many plastics are permeable to oxygen, which in the carrier gas will destroy your stationary phase.

I wonder how that setup was used - running two samples in parallel would roughly double throughput, but the injections would need to be simulataneous, which a single autosampler could not accomplish.

Peter

I agree with Peter. Never use plastic for your gases. Not only will they bleed, but they are porous too. If the copper is contaminated, rinse with polar and nonpolar solvents, then bake in a ventilated oven at ~100 C. Purge with gas before using to remove room air.

If you are using a compressor, make sure that your compressor is oil free. Trace petroleum will cause visible contamination in your chromatograms.

Sorry sorry sorry... never thought that the plastic tubes will bleed. Then i'll have to shorten one copper tube because it was bent so hard that there is a tiny hole in it.
/Alvin

Sorry sorry sorry... never thought that the plastic tubes will bleed. Then i'll have to shorten one copper tube because it was bent so hard that there is a tiny hole in it.
/Alvin

Hi Alvin

I would replace the copper tube - unless the ends were sealed it is probably full of dust. You also need a gas scrubber on your carrier gas, and activated charcoal filters on the gasses to the detector.

Peter

If you replace the tubing with anything but analytical grade copper tubing, I recommend solvent rinsing the tubing to get the oil out; then purge or bake out the solvent.

I learned these things the hard way.

It came actually with the ends sealed. I managed to cut the copper line and put the end back on, is about 40cm shorter but better than nothing.
It will take a while until i will get it running, i'm still missing the PC, H2 tube and coal filters. The gas costs almost nothing, but the tubes are really expensive. I already have a 5liters N2 tube i'm wondering if it's too small?

Cheers!!
/Alvin

Hi Alvin

I would replace the copper tube - unless the ends were sealed it is probably full of dust. You also need a gas scrubber on your carrier gas, and activated charcoal filters on the gasses to the detector.

Peter

Hi Peter,

Can you recommend a specific type of charcoal filter?

Kind regards,
Alvin

HI Alvin

A filter from any of the GC manufacturers, or the spares and consumables companies like Supelco and Restek will do the job.

Peter

If you replace the tubing with anything but analytical grade copper tubing, I recommend solvent rinsing the tubing to get the oil out; then purge or bake out the solvent.

Refrigeration grade or analytical grade copper tubing.

If you replace the tubing with anything but analytical grade copper tubing, I recommend solvent rinsing the tubing to get the oil out; then purge or bake out the solvent.

Refrigeration grade or analytical grade copper tubing.

Sometimes refrigeration grade can have residual oils left in it. It is more clean that what would be used for water or natural gas, but still not certified analytical grade clean.

Hi guys!

After a looong time with my plans on ice i'm back again on setting up my GC. I found an old computer compatible with the Varian Star ws software, found an antique PCI network card with BNC and now i can find the GC in the software. I have H2 and N2 on the way both 99,9999%, filters, new copper lines from Agilent and a lot of other parts. So in a few days ill might have everything up and running for good.
But the thing is that i would like to be able to detect traces of pesticides and i wonder if only the FID without a MS will do?

I checked in all the manuals of the GC but i can't find any info if it can work together with a MS from other manufacturer like Finnigan. What i can see the finnigan has a GPIB port but i hope is not 110V because it comes from US...

All tips and tricks from the experts are highly appreciated =)

Cheers!!
/A