Pesticide standard expire date

[Maja]

I have run some herbicide standards that are very old (maybe 10 years or more). I got more than 1 peak with everyone of them. Is it the method or the standards are degraded?
Do pesticide standards have expire date and what is the possibility that they are degraded?

Thank you for any reply.

[Russ]

Most pesticide standards have expiration dates. While some may depend on storage conditions, most standards I have used have expiration dates significantly less than 10 years. However, if by more than one peak you mean that the peaks are split (peaks at close to the same retention time), there could also be an instrument problem. You could try getting a new standard for one and see if that fixes the problem.

[Ron]

Pesticide standards do not generally degrade quickly if they are kept in a freezer in the dark. Some will degrade over time, but I have used standards 10 years old that have still been good. Do you have a lot of smaller peaks or all they all about the same size? Most pesticides are in the purity range of 95 to 98% purity, so some smaller peaks are not surprising. Multiple large peaks could be an indication of degradation.

[Maja]

Thanks for your reply.

I usually get sharp small peak followed by a large and wide peak.
Is it possible to separate acidic herbicides (2,4-D, 2,4-DB, 2,4,5-T), bentazon and triazines (atrazine, simazine) in one run, with one method?