Chromatography Forum

Hi,

I am hoping to get to the bottom of a split/splitless issue I am having. All of the methods I am reading call for a split ratio of 1:10 or 1:20. When I edit the method in chemstation, no matter what i input for the split ratio, the ratio reverts back to 1:1 once I've closed out of the method editing window. Also, in the instrument drop down tab in chemstation, the split/splitless option is greyed out and cannot be edited from here. Am I missing something? Thanks in advance!

-Nicole

Does the software have the inlet as a split/splitless injection port in the hardware configuration?

If it is detected incorrectly as a Direct Inject port or something other it would block out the choice for split injection.

Does the software have the inlet as a split/splitless injection port in the hardware configuration?

If it is detected incorrectly as a Direct Inject port or something other it would block out the choice for split injection.

I am not sure how to tell?

Hello

Check it on GC display:

1.Click "config" button
2.Then click "Front or Back Inlet" - depends where you have your inlet
3.See if it is configured properly (make photo and paste it here)
4.It should have Split\Splitless inlet in configuration
5.Check if you can change parameters (split ratio, pressure, mode) manually on GC display and if GC accepts all changes - this will help to narrow it down to GC problem or Chemstation issue


Regards

Tomasz Kubowicz

Thank you. My GC does not have a 'config' button however I did take pictures of the GC display and the info I was able to find about split flow. When I tried to change the split flow from 0 to 2ml/min, it reverted back to zero once I exited the flow settings. Please see images below..

In the first photo it appears you have an older 5890 with the manual split/splitless controller. With that you must use a flow meter and measure the flow coming from the fitting on the left and set the flow with the knob above it until you get the desired split flow. If you have 1ml/min column flow and you want 10:1 split ration you have to adjust the knob until you have 10ml/min flow from that fitting on the flow meter. Any setting you enter on the keypad will do nothing for that inlet.

To set the splitless time for the run you will need to go to the menu on the last photo and use the Purge Valve menu. In that you should be able to set the On or Splitless time to zero or initial, then the Off or Split time to whatever time you want the inlet to go into split mode to flush out the inlet. It has been a while since I used one of those so I am not certain what the exact options are, but that should get you to where you need to be. It wasn't until they went with the full EPC that you could completely control all of the flows from the computer.

If your has the flow sensors, you might see the B: Split flow increase when you turn the knob counter clockwise, if so then you can just set the flow using the display reading instead of needing a separate flow meter.

In the first photo it appears you have an older 5890 with the manual split/splitless controller. With that you must use a flow meter and measure the flow coming from the fitting on the left and set the flow with the knob above it until you get the desired split flow. If you have 1ml/min column flow and you want 10:1 split ration you have to adjust the knob until you have 10ml/min flow from that fitting on the flow meter. Any setting you enter on the keypad will do nothing for that inlet.

To set the splitless time for the run you will need to go to the menu on the last photo and use the Purge Valve menu. In that you should be able to set the On or Splitless time to zero or initial, then the Off or Split time to whatever time you want the inlet to go into split mode to flush out the inlet. It has been a while since I used one of those so I am not certain what the exact options are, but that should get you to where you need to be. It wasn't until they went with the full EPC that you could completely control all of the flows from the computer.

If your has the flow sensors, you might see the B: Split flow increase when you turn the knob counter clockwise, if so then you can just set the flow using the display reading instead of needing a separate flow meter.

Yes I am using a 5890 Series ii. I turned the knob to open the flow at the split fitting and I do not get any flow coming out of it. I set the purge valve to be on for 1 minute and I still do not get flow through the fitting.

Do you have good flow through the column?

What is the head pressure at the inlet?

If there is not enough head pressure to have excess flow then there will be none at the outlet.

The instrument is sensing it as a Packed Column inlet, can you send a photo of the inlet at the top of the instrument to verify it has split capabilities?

Do you have good flow through the column?

What is the head pressure at the inlet?

If there is not enough head pressure to have excess flow then there will be none at the outlet.

The instrument is sensing it as a Packed Column inlet, can you send a photo of the inlet at the top of the instrument to verify it has split capabilities?

At 60*C I get 19.5psi. I am using a restek column, Rxi-624Sil MS Column (fused silica) .25 diameter and 30m long. Here is a picture of the inlet...

I am also using a headspace auto sampler that is attached via transfer line.

I guess it might be wise to note that I have been working on this GC for about a year now and this is the only GC experience I have. The company I work for bought it and asked me to figure out how to use it, develop, and validate methods using it. I am self taught and have come a long way however I feel I may be missing some of the basics.

I wanted to make sure it was the proper inlet, which it is. Now I am wondering why the instrument is thinking it is a packed column inlet in Chemstation. From the menu you have in the photo of Chemstation Split is grayed out but Packed Column flow control is active. Which version of Chemstation do you have?

There should be a menu that shows the hardware setup on Chemstation, if we can find that maybe there is a way to tell the software it has the Split/Splitless port instead of the Packed Column port. If it is not a setting there, then the GC itself is confused as to which port is installed, but if it is then it shouldn't be showing the split flow readout on the panel. I will have to look through my old manuals tonight and see what I can find as to how you tell the GC what it has installed, has been to many years since I set one up.

I am also using a headspace auto sampler that is attached via transfer line.

This might be contributing to your problem. Take the headspacer out of the line and reconnect the carrier feed direct to the inlet. Then check for split flow and septum purge flow.

Peter

The P&T should not be a problem if it is connected to the correct line at the injector. It's difficult to see if the correct line has been spliced. The one to use is the line that goes into the "flat" part. There are 2 lines there, one is welded into the round part, and one into the flat. The line going into the flat should be cut and the P&T put in series. The cut closest to the injection port should be connected to the P&T's transfer line (one that is covered with the heating blanket), the 2 lines left should be connected to each other. I have always connected my P&T's this way with no problems.
The injector is S/S, and if you get the flows correct, what does it matter if Chemstation thinks it is a packed injector? The detector output to Chemstation is what matters.

In the 'about your GC' menu I get this list of hardware however, it is not editable.
ChemStation Rev.A.10.02

****Parameter Settings for 5890 GC****
Series II, 6 channel EPC
Detector A = FID
Detector B = Not Present
Flow Sensor Not Present
Injector A Heater Not Present
Injector B Heater Present
Detector A Heater Present
Detector B Heater Not Present
Aux Gas Not Present
EPP A Not Present
EPP B Present
Inlet A is = S/S
Inlet B is = S/S
Aux C Not Present
Aux D Not Present
Aux E Not Present
Aux F Not Present
Autosampler Not Installed

I don't feel comfortable removing the transfer line from the injection port. I have not disassembled the GC nor the Headspace before. I have only changed the liner and cleaned the inlet and detector. I do not have any local resources or mentors to help me and I have found it difficult to find disassembly videos or tutorials.

Also, I was able to get flow from the fitting at the bottom left of the front panel. The fitting reads split/splitless inlet purge... In the purge valve menu I set inj. B to On from 0.00 to 1.00 min. I now have flow coming out of that fitting. It does not seem to affect my chromatograms though. I can change the split flow in the GC flow menu but it reverts back to 0 once I have exited the menu. I can turn the knob above the purge valve and it does not change the reading on the GC panel nor in chemstation. I do not have a flow meter as that is out of the budget. I know I have flow now because I attach a piece of column to the valve and bubble it through isopropanol.

In the 'about your GC' menu I get this list of hardware however, it is not editable.
ChemStation Rev.A.10.02

****Parameter Settings for 5890 GC****
Series II, 6 channel EPC
Detector A = FID
Detector B = Not Present
Flow Sensor Not Present
Injector A Heater Not Present
Injector B Heater Present
Detector A Heater Present
Detector B Heater Not Present
Aux Gas Not Present
EPP A Not Present
EPP B Present
Inlet A is = S/S
Inlet B is = S/S
Aux C Not Present
Aux D Not Present
Aux E Not Present
Aux F Not Present
Autosampler Not Installed

I don't feel comfortable removing the transfer line from the injection port. I have not disassembled the GC nor the Headspace before. I have only changed the liner and cleaned the inlet and detector. I do not have any local resources or mentors to help me and I have found it difficult to find disassembly videos or tutorials.

That printout shows that the GC is not equipped with a flow sensor so you won't get any reading from the flow. It also has the manual flow control knob so changing the settings will not do anything to the actual flow.

The split ratio will have to be measured by the flow from the column and the flow from that front left port. If you have a burette in the lab you can make a soap bubble flow meter using a Tee connector, some tubing and a dropper bulb. Attach a short piece of tubing to the tip of a burette, then to a Tee connector so that the Tee connector is through from top to bottom and the middle port is to one side. Connect the side port to a piece of tubing going to the GC outlet and place a dropper bulb filled with soap solution on the bottom port. Once the gas is flowing just squeeze the bulb to introduce enough soap solution so that you get bubbles flowing up the burette, then use a timer to measure ml/min flow. This is how we did it before we had digital flow meters

If you measure the flow out of the column and the flow out of the split vent, then you have the split ratio( 5ml column and 50ml vent flows would be 1:10 split ratio)