Simultaneous LC–MS/MS determination of 40 legal and illegal psychoactive drugs in breast and bovine milk

•A LC–MS/MS method was developed to determine 40 psychoactive drugs in milk.•The method allows the investigation of 10 drugs for the first time in milk.•Method was validated in breast milk and four different classes of bovine milk.•Caffeine was the only compound found to be present in the milk samples analysed.