Chromatography Forum

I am currently using an Agilent G1888 Headspace Sampler and have used the old 44 vial 7694 Headspace analyzer.

Both support shaking the vial in the oven but I have never tried to use the shaking function. My thought when developing a method was if it worked without shaking then don't bother even trying, because it added another possible variable (consistency of the shaking) as well as adding the possibility of instrument failure (moving parts break more often).

So what does shaking help? What problem(s) does it solve?

Thanks,
- Karen

In larger volume samples it allows faster equilibration of volatiles than would be achieved without mixing by shaking. This can improve repeatability Also some samples may not dissolve unless heated and the shaking improves the complete homogeneity of the sample for improved repeatability.

Only use it when you need it. If you don't need it, then no worries.

best wishes,

Rod

We have an old Tekmar 7000 that we use for Methanol and Ethanol testing. One day the shaker motor quit working and we couldn't get one in for a couple of days. As we had some rush samples, we tried to run it without the shaker motor and we found that responses increased dramatically.

Using the agitation increases the response of volatiles in your sample as more are realised into the headspace. This is especially useful with volatiles that are very miscible in your sample diluent and are reluctant to leave it. A mixture of agitation, increased heat and longer vial incubation time can improve response.

We have an old Tekmar 7000 that we use for Methanol and Ethanol testing. One day the shaker motor quit working and we couldn't get one in for a couple of days. As we had some rush samples, we tried to run it without the shaker motor and we found that responses increased dramatically.

That's interesting, and unexpected. Please tell us more.

Peter

This indicates that either a reaction with the alcohols was occurring or your vial closures were not secure and the vibration was causing leaking of the vials.

Right?

best wishes,

Rod