Keywords: trace analytics stream pesticides pyrethroids Substances: Bifenthrin (OXCDWLBJSLVWHB-LKRLXIKPSA-N) Cyphenothrin (FJDPATXIBIBRIM-UHFFFAOYSA-N) Tefluthrin (ZFHGXWPMULPQSE-SZGBIDFHSA-N) Empenthrin (YUGWDVYLFSETPE-JLHYYAGUSA-N) Chlorpyrifos-methyl (HRBKVYFZANMGRE-UHFFFAOYSA-N)