S1 certification of alpha-endosulfan,beta-endosulfan,and endosulfan sulfate in a candidate certified reference material (organochlorine pesticides in tea) by isotope dilution gas chromatography-mass spectrometry
1. Government Laboratory, 7/F., Ho Man Tin Government Offices, 88 Chung Hau Street, Ho Man Tin, Kowloon, Hong Kong Special Administrative Region, China