Paraquat (or N,N′-dimethyl-4,4′-bipyridinium dichloride) and Diquat are are very frequently used herbicides worldwide.
The use in agriculture is regulated. A determination in grains, fruit and for instance chiaseeds is important and highly recommended.
Commission Regulation (EU) 2016/1002
(Maximum residue levels for AMTT, diquat, dodine, glufosinate and tritosulfuron in or on certain products)
Regulation (EC) No.396/2005
(Maximum residue levels of pesticides in or on food and feed)