I have 800 µl of sample buffer stocks (without DTT) stored at -20°C. Before using I add 2.5 M DTT and use it.
Sometimes, I add the sample buffer to my samples and store at -20°C. However, the next day after heating the samples, the color of the buffer changes from blue to dark green. But, when I load it to the gels, they appear blue. Why does the color change after heating.
After adding the buffer to the sample, should I store the buffer at -20°C for next day use or should I store at RT. How long can the buffer be stored (days, weeks?) at RT or -20°C?