What's the reason that alkanolamines change their color at storage? What's the reason that alkanolamines (e.g. monoethanolamine, diethanolamine, triethanolamine) of technical purity change their color (from colorless over yellowish to red-brown) at storage?
Is it because of oxidation, or UV-light?
Oxidative degradation by oxygen certainly occurs and has been studied 1, 2. I can't access the papers so I have no information on possible mechanisms. I've seen no mention of UV degradation, but that doesn't mean it does not happen.