Autosampler mobile phase flow diagram-Chromacademy tutorial

[hplctroubleshooting]

Pertains to : LC Waters 717 plus autosampler and the autosampler tutorial for the LC on http://www.chromacademy.com/lc-hplc-overview.asp , section 7


Issue: We're getting lower areas then usual with some variability in our recent runs. I suspected that the autosampler needle was being an issue, perhaps something had gotten into it while it was puncturing one of the vials. After replacing the needle-by first disassembling the entire injection platform, a leak was observed at the top of the needle where it connects to a tubing that leads to a valve- apparently I had forgotten to connect a tubing to the top of the autosampler needle.


http://api.ning.com/files/xj4ucqERBnSPB ... needle.bmp

I was observing section 7 on the Chromacademy tutorial for the LC autosampler and according to the flow diagram of step one, the flow isn't even supposed to go through the needle, other then when the syringe is pulling or pushing out its contents.

Does this mean that I have a damaged seal pack? Why was the needle connected to the flow of the mobile phase when no injection was being made? That is, while the machine was simply supposed to be pumping mobile phase through the column without any program being implemented?

This would certainly explain the reduced areas since the sample contents within the needle are being diluted before it gets pushed out into the system.


Please observe the attached diagram for details and ask follow up questions if there are any. Really would appreciate any input from the experts here.

[nkg]

the 717 and 2695 use the same design for the autosampler. there is a constant flow through the needle during normal opration, the needle is isolated from the flow during sample aspiration.
when you rebuilt the injector did you run seal pack adjustment afterwards? also have you carried out a purge / compression of the autosampler? when you have done these it might indicate a fault on one of the valves which is causing your problem.

[hplctroubleshooting]

the 717 and 2695 use the same design for the autosampler. there is a constant flow through the needle during normal opration, the needle is isolated from the flow during sample aspiration.
when you rebuilt the injector did you run seal pack adjustment afterwards? also have you carried out a purge / compression of the autosampler? when you have done these it might indicate a fault on one of the valves which is causing your problem.

thanks for your input. How is it running the flow through the needle AND to the column at the same time, that would mean that the flow of the pump diverges to both the needle and the column line (tubing that leads out of the autosampler to the column), please refer to the diagram in the OP for reference to an actual picture.

I'm a bit naive to some of the terms that you mentioned, such as your reference to the "seal pack adjustment". Could you perhaps point me to some resources on this topic or maybe explain a little bit yourself on how to carry out this procedure?

I've done a compression test on the autosampler during a previous period where I was basically having similar issues-replacing the needle and the seal pack seemed to do the trick in this case. After the test, the autosampler display really didn't say much, I figured that since no issues were indicated that there were no issues with any of the valves.

I also tried testing for the valves with the "valves motion" option. Pushed "set up" and that's about all it does other then the message "ready for set up" popping up, with which I'm not quite certain what it wants me to do after that.

[nkg]

do you have the operators manual for the 717? also let me know your email address and I can send you the relevant info for the injection sequence during a run / injection, I can also send you the 717 manual if you haven't got it,which describes the operations you need to do to verify instrument performance

[hplctroubleshooting]

do you have the operators manual for the 717? also let me know your email address and I can send you the relevant info for the injection sequence during a run / injection, I can also send you the 717 manual if you haven't got it,which describes the operations you need to do to verify instrument performance

I found the 717 plus manual online, I got to the point of adjusting the seal pack but the calibration itself seems pretty tricky. It needs the pressure to be between 400 an 600 psi, but just going by the correction for the transducer versus the system doesn't seem to quite have a trend.

email address is gcttutor@hotmail.com

[Bull76]

Hi,

Once you have a column on the system, I use a symmetry C18 column 100mm. This provides the enough backpressure for the system to complete the adjust seals.
You have a restrictor loop which the flow goes through once the injector is making an injection or the needle is placed into the seal. This is because V1 is closed and this isolates the injector. V2 and v3 are open during the injection phase.

Regards,
Bull76

[hplctroubleshooting]

Hi,

Once you have a column on the system, I use a symmetry C18 column 100mm. This provides the enough backpressure for the system to complete the adjust seals.
You have a restrictor loop which the flow goes through once the injector is making an injection or the needle is placed into the seal. This is because V1 is closed and this isolates the injector. V2 and v3 are open during the injection phase.

Regards,
Bull76

thanks for your advice, will try out your suggestions with the c18 column once I get to that stage, just trying to calibrate my seal pack right now, posted another thread about this dilemna.