Hello, first post but I have been a secret lurker for a while.  This might be a newbie question, but I am running into a wall with finding an answer.  

I will be setting up a several nitrate standards from KNO3, but I wish to preserve the samples so they can be used at several facilities. Several questions Z am looking to solve:

1)  How long can I expect standards to stay accurate when prepared with DI water without refrigeration? Hours, days, weeks?

2) Is there a method for stabilization without chloroform? I am not sure how to get it and how to safely store it (my lab is very very basic).

Thanks in advance;
Matthew