Refrigeration may be good for the short-term storage of samples. Sample containers should be inert glass, Teflon or stainless steel.
We also recognize that the sample storage issue is important, with many opinions. It is always a point of consideration because the ideal would be real-time analysis but that is not practical. We can see the scientific justification for both freezing and storage at 2–8°C. Precipitation and phase separation are risks when freezing extracts, but storage at 2–8°C may lead to the degradation of extractables (oxidation/hydrolysis, etc.) or loss of volatiles.
Our baseline is that, barring a perfect solution, we leave it to the analytical laboratories to justify their approach as being reasonable.