I need you help regarding Proficiency testing and PT provider in pesticide formulation
I cannot recommend any providers as it depends on your scope and area. Have a look at EPTIS at https://www.eptis.org for posisble providers. This is an International database of Proficiency Testing (PT) schemes.
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I need your help with regard to PT testing as we couldn't find any in our scope .is there any alternative?"
What I suggest you do is contact your accreditation body as well, as they will need to approve the alternative which typically would involve a bilateral study between yourself and one other laboratory or the use of certified reference materials for your own study.