Chromatography Forum

Hi All,
Currently running a basic FID test mix (C14,C15,C16) and looking to achieve area uV/sec >200,000 for the instrument to pass operational qualification stage.

When using a manual injection this is great as consistently getting >600,000 however when I change to using the autosampler the areas significantly reduce to anywhere between 25,000 and 250,000 (usually at the lower end).

There doesn't seem to be a particular pattern to when spec passes. I have performed full system maintenance including change of autosampler and syringes but the same issue occurs.

Any ideas?

Thanks in advance.

Is there enough solvent in your vials, i.e. can the syringe withdraw a consistent amount of sample? And what injection volume are you using?

There is 1mL of sample in the vial and can easily withdraw enough; I've even watched the autosampler to ensure no air is getting into the syringe. Injection volume is 1uL

Third time lucky with another autosampler plus a user defined programme of a pre-injection delay seems to resolve the issue.

Third time lucky with another autosampler plus a user defined programme of a pre-injection delay seems to resolve the issue.

That is sometimes the resolution to the problem if the solvent is not pulling up into the syringe quickly. Agilent I know has a box in the autosampler setup for Viscosity Delay, newer software also has plunger speed that can be set slower to reduce problems.