1. a Division of Testing and Applied Analytical Development , U.S. Food and Drug Administration , St. Louis , MO , 63101 , U.S.A.
2. b Pharmaceuticals Division , U.S. Pharmacopeia , Rockville , MD , 20852 , U.S.A.
3. c Department of Chemistry , Lafayette College , Easton , PA , 18042 , U.S.A.