1. Department of Chemistry and Biochemistry, South Dakota State University, Box 2202, Brookings, South Dakota 57007, United States
2. Beckman Laser Institute and Medical Clinic, University of California, Irvine, California 92612, United States
3. Analytical Toxicology Division, United States Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Aberdeen Proving Ground, Maryland 21010, United States