DETECTION OF N-14 AND CL-35 IN COCAINE BASE AND HYDROCHLORIDE USING NQR, NMR, AND SQUID TECHNIQUES

Results from N-14 pure NQR of cocaine in the free base form (cocaine base) yield a nuclear quadrupole coupling constant (NQCC) e(2)Qq/h of 5.0229 (+/-0.0001) MHz and an asymmetry parameter eta of 0.0395 (+/0.0001) at 295 K, with corresponding values of 5.0460 (+/-0.0013) MHz and 0.0353 (+/-0.000S) at 77 K. The NQR peaks of a sample of cocaine base containing similar to 1% impurities are a factor of 3 broader than those of a recrystallized sample, but spin-lattice and spin-spin relaxation times are essentially unchanged, Both pure NQR (at 295-77 K) and a superconducting quantum interference device (SQUID) detector (at 4.2 K) were used to measure the very low (<1 MHz) N-14 transition frequencies in cocaine hydrochloride; at 295 K the NQCC is 1.1780 (+/-0.0014) MHz and the asymmetry parameter is 0.2632 (+/-0.0034). Cocaine hydrochloride exhibits a broad Cl-35 pure NQR resonance at 2.53 MRz. The Cl-35 NMR spectrum at 7.0 T is that of a central 1/2 --> -1/2 transition greatly broadened by second-order quadrupolar effects. Stepping the carrier frequency enables one to obtain a powder pattern without the severe intensity distortions that otherwise arise from finite pulse power. A powder pattern simulation using an NQCC value of 5.027 MHz and an asymmetry parameter eta of 0.2 agrees reasonably well with the experimental stepped-frequency spectrum, The use of pure NQR for providing nondestructive, quantitative, and highly specific detection of crystalline compounds is discussed, as are experimental strategies.