Chromatography Forum

I am fairly new to chemstation, and was wondering if there was a way to pause a sequence (Agilent GC 7890) in order to add samples before the final bracketing CCV was injected. I am going to be analyzing batches of insecticide for a number of actives. The sequence will most likely be started just before I recieve the batch from the mixing technicians, so that the system can equlibrate, the diluent blank can be injected, and the intitial CCV can be injected. The actives have a somewhat tight spec, the batches are pretty large (>10k lbs), and the precision of weighing batch components is to the nearest pound (this could be better, and is the reason for my statement below)

What I am anticipating happening from time to time is that I will inject my system suit, then my samples in duplicate, and they will fail. This would need either more of the insecticide intermediate in the batch (if samples fail low), or more of the batch made, minus the intermediate (if samples fail high) and add this mixture to the batch. What I want to aviod is injecting another system suit, which will take an hour or so if I can simply pause the sequence and wait for the adjusted batch sample to inject.

On a side note, would there be any GLP/GMP problem with this? I worked in a pharma lab before, and the LCs would have a problem finding the next vial in a sequence, but the system could simply be resumed from where it left off if the mobile phase ran continuously, so I am assuming the same would work for GC. (Let me know if this is not the case).

Additional side note: I am just finishing writing this method (first time ive done this from scratch), and my system suit will include two test injections to equilibrate, a diluent blank, and a CCV injection. The samples will be injected in duplicate, and bracketed with another CCV. There is no extraction or filter process, so I am not including a surrogate or internal standard, and the samples will be quantitated using a 5 point initial calibration curve. This sound good enough?

Thanks
Sam

Use Partial Sequence function?

Dear Sam,

I have been working on Chemstation for a while now. And yes you can Pause the sequence. You should be able to see a yellow bar below in your default screen. When you press pause the sequence will end the current run and wait untill you say the sequence will start again. Quite simple.

When a vial is not present you will get an error and you will be able to start again. You proberly know what to do when it happens.

The calibration, when set up properly, is good enough. The ISTD is used for correction during preparation.

Good luck with it.

Regards,

Wouter de Graaf

I haven't been using ChemStation for about a year now and I forgot exactly where it's at but where you set up your samples there's a drop down menu where you can choose "keyword" (I'm assuming that drop down box has something like "inject" or "run" already chosen) and then you can choose "pause" in another drop down box (among many other things). This will cause your instrument to pause once it hits that line.