Headspace Transferline to front 6890N inlet w/7683 tower

[Bigbear]

The 7000 will use gas in standby to sweep the loop and exit through the needle. I think you can adjust this whhile in standby but you would have to crank it up when running to reduce caryover.
I may have inserts somewhere. WIll check.

[MSCHemist]

Thanks I think I will try to hook the epc right up to the plumbing past the manual controller (mainly because I need the reducing union for the aux epc). I think I will use the auxEPC to control the vial pressure. I'll have to work on that later as I need to order some more swagelok ferrules and vent the MSD so I can open up the aux epc gang fitting and switch out the resistance frit to a 0 resistance brass.

[Peter Apps]

Just a thought. The vial pressure control is almost certainly a front-pressure controller, so you need the equivalent auxillary EPC. An EPC designed for a split-splitless inlet has a mass flow controller for the total flow and a back-pressure controller for the inlet pressure. To use one of these for vial pressurization you have to have a T in the line going to the headspacer six port valve so that the extra pressure can bleed off through the back-pressure regulator.

Edit: or run the Aux EPC in splitless mode.

Peter

[Bigbear]

I checked and found we have some spares including the small vial inserts and removal tool. I also found a manual for the 7000. All this is yours for the price of shipping about 15 lbs from Vt.

[MSCHemist]

Thanks my work email is sschoenfeld[at]innovaflavors.com. I checked with Tekmar and they still sell the collar which you also need for smaller vials but they don't carry the inserts. I have the manual and the pdf is available online. It gave me some more issues with splitless this morning so I am going to bypass the controller and 1/8" plumbing. It has no problems with split though I ran 30 raw materials with the 7683 and a 500:1 split and it had no issues.

[MSCHemist]

HI Bigbear when you have a chance please shoot me an email at sschoenfeld[at]innovaflavors.com so I can arrange shipping for the inserts. If you have an extra reducing collar for the 7050 carousell we'd be happy to buy that off you as well.

BTW how many do you have. I though I could just get one and keep using one platen position but the manual states if you don't put one in each platen position it could abort the run.

[MSCHemist]

Hi Peter I just saw your last post. The aux EPC when setup with an Agilent 7694 has a bleed weldment of some sort just before the instrument. With the 7000 it goes to the manual flow controller which provides resitance and sets the flow rate as there is none in the aux epc they recommend a zero holed frit and then to a pressure regulator that is set to whatever the pressure you want the vial at.

SO you are saying that if I use the auxEPC it could overshoot the pressure when filling the vial and have nowhere to bleed to reach the pressure set point. The flow controller is set to limit the flow rate through the needle so it builds up slowly perhaps so that won't happen but if it comes down to it I can always set the pressure on the aux epc higher and use the manual pressure valve to set the maximum allowed (setpoint) vial pressurization pressure.

Man I had no idea what I was getting into with this instrument. I thought it would be simple cut the epc and hook it up.

[Peter Apps]

Hi Peter I just saw your last post. The aux EPC when setup with an Agilent 7694 has a bleed weldment of some sort just before the instrument. With the 7000 it goes to the manual flow controller which provides resitance and sets the flow rate as there is none in the aux epc they recommend a zero holed frit and then to a pressure regulator that is set to whatever the pressure you want the vial at. There is no point in having two pressure controllers in series, if you are gong to plumb through the Tekmar vial pressure controller anyway, then just take the gas straight off your house supply

SO you are saying that if I use the auxEPC it could overshoot the pressure when filling the vial and have nowhere to bleed to reach the pressure set point.That's about it - although I believe that some Agilent EPCs are just front pressure controllers, so if you have that kind you could bypass the Tekmar pressure control The flow controller is set to limit the flow rate through the needle so it builds up slowly perhaps so that won't happen but if it comes down to it I can always set the pressure on the aux epc higher and use the manual pressure valve to set the maximum allowed (setpoint) vial pressurization pressure same comment as in para 1 - one of the pressure controls will be redundant. If the EPC has a total flow setting (i.e. like a split splitless inlet EPC) you could use that to control the flow rate into the vial, and the pressure setting to limit the max vial pressure. I would be wary though that if the vial pressure overshot by even a little bit the back-pressure regulator would bleed some of the headspace out to control the pressure, leading to poor repeatability. There is another issue of where the EPC will read pressure - as far as I know Agilent puts its inlet pressure sensors in the septum purge line, which will not have a direct equivalent in the set up that you propose.

Man I had no idea what I was getting into with this instrument. I thought it would be simple cut the epc and hook it up.

Now you know why when I did headspace I swapped out the loop for a 100 ul and ran with a direct connection to the column

Peter

[MSCHemist]

I am sure it reads the pressure at the EPC module at there is no mechanics or anything down stream. It simply consists of a gas feed, exchangable restance frit (to vary resistance Agilent says use a zero resistance frit which is simply a brass tube, with vial pressurizers), the electronics and sensors and then a length of attached 1/16" tubing which you plumb to whereever or whatever.

I know some models of the Agilent 7694 headspace sampler which is a very similar instrument to the Tekmar 7000 are designed to be run with an aux epc as I described. The only difference is this bleed weldment which doesn't look like it has any sensors or electronics I think it is just a safety release mechanism.

As for having two pressure modules If I wanted to bypass that as well I could use a T after it comes from the flow controller that sets the resistance and then has a branch that goes to a dial vial pressure needle guage but I don't think leaving it in the pathway would interfere with anything. It also could serve as an extra safety device as long as it is set higher than the auxEPC pressure it shouldn't interfere unless the aux EPC allows it to go grossly overpressure in which case it should limit it.

I like the idea of using the EPC as it is easy to turn off or down when not in use and easy to switch pressures between methods.

[MSCHemist]

I just thought I'd update everyone. I finally got the swagelok ferrules I needed to complete the plumbing.

I bypassed the manual flow controller and my EPC is much better. It had gotten to the point where I could not do splitless at all as it would overshoot then drop below then overshoot and never reach the set point. I opened the right pannel of the 7000 and right below the manual transferline flow controller is a short length of 1/16" steel tubing goint to a T that connects a needle pressure indicator and the line going to the valve. I unhooked that line and hooked in some 1/16 line connected directly to the inlet. That solved all the issues I was having.

[MSCHemist]

According to the manual I can use 12, 9 or 22 ml headspace tubes but with 12 and 9's I need a smaller collar to reduce the size of the aperature in the carrousell that the vial falls through and sleeves to take up the space.


However, the only difference between6,10 and 22ml headspace tubes are height. Is there any way I could use the same stupid collar since they all have the same diamter, and get some sort of insert to take up the heigt difference between a 6ml and a 22ml? If so where can I find it.

[Bigbear]

MSChemist, please double check your e mail address as mailings I've tried have bounced back to me.

Bear

[MSCHemist]

I recieved it thanks.

Been busy working on it. It has a blown platen motor, the sample and vial motors I was able to rescue by cleaning the webbing and gears with cotton tips and isopropanol. I ordered a replacement motor for the platen. As I said the inlet issues were resolved by bypassing the 1/8" tubing and manual controller and hooking up the 1/16" tubing to the internal T. I've hooked the vial pressure feed up to an aux EPC with nitrogen.