Decreasing Standard Response

[BenNC]

I have a standard that appears to be losing peak area over time. Multiple injections from the same vial show a downward trend of about 2% over a 24 hour period. A freshly loaded vial gives a response comparable to the original injection of the standard. The solution was stored at 5°C and the autosampler was also set at 5°C, so both were stored at the same condition other than the container (volumetric flask vs sample vial).

This may also be happening with the sample solutions, but I don't have the repetitive injections of a sample.

Does anyone have any experience with interactions between vials and sample solutions? Any input is appreciated.

Thanks

[Kostas Petritis]

Interaction between your vial and your sample is a possibility. You may want to change to plastic ones at the place of glass or the other way round.

Other possibilities can be, degradation of your compound.

The more your sample is diluted the more you may notice such problems.