Materials and methods Materials. Gold label pyridine, S-(-)-nicotine and triethylamine were purchased from Aldrich, Milwaukee, WI, USA. R-(+)-Nicotine was prepared by the method of Bowman et a1 (1982) by resolution of RS-(+)-nicotine (I) with di-@-toluoy1)-(+)-tartaric acid. N-Methylnicotinium iodide (11)(NMN), N'methylnicotinium iodide (111)(N'MN) and N, N'- dimethylnicotinium diodide (IV)(DMN) were prepared by the reaction of either R-(+)-, or S-( ...