Acknowledgements are made to the following persons who have collaborated in establishing and verifying the procedures described in this document:

Professor H.Y. Aboul-Enein, Drug Development Laboratory, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia; Professor I. Addae-Mensah, Department of Chemistry, University of Ghana, Legon-Accra, Ghana; Dr E.O.P. Agbakwuru, Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Benin, Benin City, Nigeria; Dr S.L. Ali, Association of German Pharmacists’ Central Laboratory, Eschborn, Germany; Mr J.P. Billon, Rhône-Poulenc, Centre de Recherches, Vitry-sur-Seine, France; Professor P.F. Coville, University of Otago, Dunedin, New Zealand; Professor D. Dobrescu, State Institute for Drug Control and Pharmaceutical Research, Bucharest, Romania; Professor M.P. Gupta, University of Panama, Panama; Dr A.I. Hag Omer, Drug Quality Control, National Chemical Laboratories, Ministry of Health, Khartoum, Sudan; Dr P. Hayes, University of Otago, Dunedin, New Zealand; Professor A.W.M. Indemans, Laboratory of the Dutch Pharmaceutical Society, The Hague, Netherlands; Dr Z.A. Jan, Drugs Control and Research Division, National Institute of Health, Islamabad, Pakistan; Dr A. Kaukinen, National Medicines Control Laboratory, Helsinki, Finland; Dr K. Kawamura, Production Division, Takeda Chemical Industries, Ltd, Tokyo, Japan; Dr Ng Tju Lik, Department of Scientific Services, Institute of Science and Forensic Medicine, Singapore; Dr J.D. Nicholson, Medicines Testing Laboratory, Edinburgh, Scotland; Professor A.A. Olaniyi, Department of Pharmaceutical Chemistry, College of Medicine, Faculty of Pharmacy, University of Ibadan, Ibadan, Nigeria; Dr P.R. Pabrai, Corporate Quality Assurance, Ranbaxy Laboratories Ltd, New Delhi, India; Dr M. Pesez, Roussel-Uclaf SA, Romainville, France; Professor M. Rafiee-Tehrani, Industrial Pharmacy Research Laboratory, College of Pharmacy, Teheran University of Medical Sciences, Teheran, Islamic Republic of Iran; Professor J. Richter, Berlin, Germany; Dr P.D. Sethi, Central Indian Pharmacopoeia Laboratory, Ghaziabad, India; Dr S.C. Sharma, Central Indian Pharmacopoeia Laboratory, Ghaziabad, India; Ms K. Sinivuo, National Agency for Medicines, Helsinki, Finland; Dr R. Soliman, Alexandria, Egypt; Professor Tu Guoshi, Division of Pharmaceutical Chemistry, National Institute for the Control of Pharmaceutical and Biological Products, Ministry of Health, Beijing, China; Professor L. Turakka, National Medicines Control Laboratory, Helsinki, Finland; Mrs O. Van Berkel-Geldof, National Institute for Drug Control, Leiden, Netherlands; Dr M. Vernengo, PAHO/WHO, National Institute of Quality Control and Health, Rio de Janeiro, Brazil; Dr I. Vukušiæ, Podravka-Food, Pharmaceutical and Cosmetic Industry, Zagreb, Croatia; Dr W. Wieniawski, Institute of Drug Research and Control, Warsaw, Poland.

Thanks are also extended to the following WHO Collaborating Centres and national institutions:

WHO Collaborating Centre for Drug Quality Assurance, National Institute for the Control of Pharmaceutical and Biological Products, Ministry of Health, Beijing, China; WHO Collaborating Centre for Stability Studies of Drugs, Regional and University Hospital Centre, Nantes, France; WHO Collaborating Centre for Drug Information and Quality Assurance, National Institute of Pharmacy, Budapest, Hungary; WHO Collaborating Centre for Quality Assurance of Essential Drugs, Central Drugs Laboratory, Calcutta, India; WHO Collaborating Centre for Quality Assurance of Essential Drugs, Drug Analysis Division, Nonthaburi, Thailand; State Institute for Drug Control, Prague, Czech Republic; Quality Control Department, Mexican Institute of Social Security, Mexico City, Mexico; Central Indian Pharmacopoeia Laboratory, Ghaziabad, India; Food and Drug Administration, Ministry of Public Health, Nonthaburi, Thailand.