Does TOC of WFI increases when the water is kept in depyrogenated plastic containers over a time period of 12 - 24 hrs 
When ever you use Water for Injection (WFI), you must ensure that you collect that fresh , use either in hot condition or in cool condition (by cooling it immedaitely).
When you store such water more than 3-4 hours it might automatically lose its importance.
[COLOR=“blue”]“Always use fresh WFI”.
If you store for longer periods and use you must have a authentic proof of validation supported by testing reports that the Quality of water is not altered --Especially Microbial count.[/color]
12 hour store of such water in Plastic containers does not increase TOC.
You must ensure that you will first cool that water to about 40C and then fill in such containers in a proper place so that addition of external contaminations are minimized.
24 hour storage might have problems.
TOC online & offline will have variation , upon stoage i agree with Durga .Use fresh ,avoid more than 3-4 hrs , establish all parameters