Chromatography Forum

Hi guys,

I ve noticed that my standard showing small absorbance increase (around 0.1-0.3%) every day stored at about 22C protected from light. No impurities. It is very stable product. Any ideas what's going on?

Evaporation of the solvent?

Remember that the company eliminated my job after 40+ years so I must not know anything, what I would do is prepare several separate autosampler vials and inject one of those each day when you inject the other standard. We tend to keep standards (oops, they tended) in dark bottles in the refrigerator with Polyseal cone caps, and would shake, open, transfer a ml into an autosampler vial, and re-cap. It could reach room temperature in the autosampler vial, so less evaporation when cold transfer.

We kept calibration standards typically 90 days in the refrigerator, but we had data documenting stability over that time (real-life used standards).