Autoclaved water with white flecks in it? - (Nov/16/2009 )
PhilS on Nov 16 2009, 05:22 PM said:
I prepare my own sterile water for PCR reactions. Every few months. I autoclave ~50 x 1.5 mL eppendorf tubes, each with 1 mL of water inside. The tubes are clean and the water has come from a filtered water source in our lab. When I autoclave, I cover the tops of the tubes to prevent them bursting open. The eppendorf's are then stored in a screw top jar on my bench.
However, every time, after a month or so, I start to see small flecks of white appear in the water. Before I ignored it, knowing that they were still sterile, but as I've been having trouble with contamination recently, I started to suspect this might be the source. But when I look at these specs under the scope, I do not see any cells. I'm thinking of calling the manufacturer of the tubes to ask them for their advice, but I thought I'd post here first.
Well, if it is salts then it should redisolve by shaking and/or heating.
If you put thimerosal or sodium azide at 0,1% in one of your eppendorfs and the flecks son't appear then it´s contamination.
If it is contamination you can just freeze the tubes and and place them at 4ºC just a few days before use to avoid the flecks growing without having to include extra-something to the buffer
If you water is any good, it will have essentially no salts of any kind, and will evaporate without any sort of residue. It also won't grow much (but will perhaps grow a very few bacteria, amazingly enough). Certainly not enough to actually see or to find on a microscope slide. I would worry about how pure my water was if I saw anything of any kind in it. What's the resistivity?