problems with sample analysis benzoyl peroxide

[martinamarie]

Hi there, I have previously posted but hope someone can help further.
We are analysing samples containing benzoyl peroxide and an antibiotic.
Sample solvent is 0.1 % acetic acid in acetonitrile-water (80-20 v/v)
The benzoyl peroxide seems to be degrading giving between 5- 10 % benzoic acid (even in the standard preparations containing only BPO).

We have added a cooler compartment, but this only offers slight improvement.
It seems the problem is

The system plumbed with peek tubing gives lower degradation.

We added EDTA to the sample solvent and mobile phase, and reduced degradation, however, even for the standards, with this measure in place it appears we have stability of no greater than 5 hours.
Our next step is to add an antioxidant to the solution.

Can anyone help, ive read lots of posts, and the literature and dont seem to see this problem anywhere else.
Thanks
Tina

[HW Mueller]

An antioxidant will most likely reduce the peroxide to benzoic acid, maybe that is what you want? It seems to me that one should expect trouble with peroxides, but if some people have done them successfully I would look at the pH and even at whether EDTA is properly applied.

[Consumer Products Guy]

We've only briefly assayed for BP, but I don't remember any degradation like that. I'll try to remember to check my notebook on Tuesday...