Headspace GC reproducibility problem

[gsr]

Hi all,
We have reproducibility problem with our HSGC when analyzing an amine.trend is first 2 injections response is low and then next 4 injections of working standard is consistent.we are using a capillary column with 2mm id deactivated glass liner.any suggestions pl????
thank you
gsr

[Peter Apps]

First guess has to be that you have absorptive activity somewhere - what system do you have ?

Peter

[gsr]

we have 6890 GC with HP 7694 headspace sampler.we are using DB-17 column.we already changed the injector liner thinking that it could have active sites to absorb the amine.any additional suggestions pl.

thanks in advance
gsr

[Peter Apps]

The transfer line from headspacer to GC is the next likely culprit, unfortunately it will be much more expensive than an inlet liner !

Has anyone ever tried doing an in-situ deactivation on one of these lines by injecting a silanizing agent ?

Peter

[AICMM]

GSR,

Divide the system. If you inject amine solution into inlet directly do you have the same issues? If so, it is possible that amines are reacting with inlet or column.

Also, how is your HS sampler connected to the GC?

Best regards.

[gsr]

we were planning to do that direct injection (I meant using GC autosampler)next week to narrow down the problem origin.
Iam sorry AICMM,I didn't get your question?
it is connected to GC through transfer line.

thanks
gsr

[chrom]

you are injecting the solution directly or otherwise using diluent. In our lab we tried with Highboiler solvents as a diluent.

thanks

[gsr]

hi,
we are usinmg 0.1N NaOH in DMSO(with about 2% MeOH) as diluent
thanks

[mcbart]

Have you try to use a syringe based autosampler such as HT200H?

The only part of the autosampler in contact with the sample is the syringe and so you get not anymore to worry about transfer line problems.

[mbicking]

There is an Agilent procedure to "steam clean" the headspace system. It is either in the manual or on their web site. It may help. If you cannot find it, write to me tomorrow and I can find the reference.

[gsr]

I have done "steam cleaning" before.Iam working on something else so I didn't get a chance to do it.
thanks for the suggestions