Can I use Waters Empower GC to run headspace/GC splitless?

[snow]

Waters has introduced Empower GC to run Agilent 6890 GC. I can run liquid injection, headspace/GC split mode with Empower GC, but I have difficulty to run headspace/GC splitless mode with Empower GC.

Any one has experience with Empower GC and splitless mode? How do I configure the system?

Thanks

[krickos]

Hi

In my experiance and from related earlier posts in this forum, the "issue" is not related to the software.

Simply put, splitless is hard (impossible?) with the typical standard hardware. Typically the total flow (column+split) have to be like 8ml/min or so (ie split ratio 1:4-1:5 for a typical application) to insure a decent injection. If flow/pressure is too low the typical sample plug of 1ml will enter injector and column very slowly and suffer from diffusion issues in injector.

So basicly you would need a high flow higher id column to make it work.

In order to get robust results I belive it is simpler to work with other means to increase sensitivity if thats the issue.

From Agilent:

Can the 6890GC be used in Splitless Mode with a Headspace Sampler?
Answer: Yes, but note that there are severe limitations for using Splitless mode with the headspace sampler.
Background: Typically a Splitless injection is intended to cold trap the sample in a small band on the head of the capillary column from a liquid injection in the inlet. In that case the sample does not have far to travel and low flows are okay to get the sample on the column in a reasonable length of time and in a small band on the column.

With a Splitless mode injection on the headspace there is a significant volume of tubing for the sample to go through before it reaches the inlet. With the low flows that are typical for a Splitless injection it takes a very long time for the sample to get on the column. Because of this you will encounter two problems:

1.Severe band broadening of the sample on the column. (Broad peaks)
2.Loss of active compounds due to the length of time the sample is in contact with heated pneumatic parts.

Note: Cryo-focusing or sub-ambient oven temperatures may help these issues.

Another consideration is the Split/Splitless inlet may be unstable due the low flows and greatly increased volume added to the system by the headspace pneumatics. Splitless mode can be used when the column flow is 20 to 30 ml/min with a 530um column.

[snow]

Thanks for the reply.

Headspace/GC splitless mode hardware has no problem when using Agilent Chemstation under the same GC condition.
If we switch to Waters Empower, the auto-prep function turn to off and the inlet pressure can not drop down to the set up pressure, in result the splitless mode won't allow to starting work.

[krickos]

Hi Snow

yes you are right on that part regarding the software/instrument communication part, some how I missed that part although iIhad that in the same "notes" ..sorry..

So yes software/communication can be an issue in some cases, as stated previously most isses I have encountered earlier have been more "hardware" related.

[Ron]

There is a previous thread on the forum, the inability of the Empower software to use the prep run function is a known problem. Agilent or Waters need to rewrite the Empower driver to solve this issue.