RESUMO
This paper reports a new capillary zone electrophoresis method for the simultaneous chiral determination of the enantiomers of N,N-dimethylamphetamine (DMA), methamphetamine (MA), ephedrine (E), pseudoephedrine (PE) and methylephedrine (Me-E). In this study, a number of electophoretic parameters were examined and optimized including the choice of chiral selectors, the use of short-chain tetraalkylammonium cations, the effect of chiral selector concentration, buffer concentration, applied voltage and capillary temperature. Heptakis(2,6-di-O-methyl)-beta-cyclodextrin (DM-beta-CD) and tetrabutylammonium (TBA) being the best chiral selector and buffer cation, respectively, the optimized electrophoretic conditions were found to be: 20 mM DM-beta-CD, 50 mM TBAPO(4) at pH 2.5, applied voltage at 30 kV and temperature at 25 degrees C. Under the optimized conditions, all analytes were well separated with resolution factors between 3.3 and 24.0 achieved. Using phentermine as an internal standard, the intra-day (n=8) precisions for the relative migration times and peak areas of all analytes were below 1.09%, while the inter-day precisions (n=12, 6 days) for the relative migration times and peak areas of all analytes were under 3.77%. This method has been applied to the measurement of the enantiomeric purities of the seized DMA samples. The result of the measurement could provide important clues about the possible synthetic pathways of these samples.
RESUMO
In Hong Kong, ecstasy tablets are more commonly known as "Fing Tau Yuen", literally meaning "Shake Head Pills". The tablets contain mainly amphetamine-type stimulants (ATS) including 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA), methamphetamine (MA) and/or ketamine. Adulterant such as caffeine was also detected in the tablets. This paper reports a study on the impurity profiles of ecstasy tablets from 89 seizures in Hong Kong from 2002 to early 2004. Tablet samples were extracted by diethyl ether under alkaline condition and then analyzed by gas GC-MS. The chromatograms obtained were compared. A total of 19 identified impurities were selected as markers for impurity profiling. They are different precursors, intermediates and by-products. The data matrices were examined by hierarchical cluster analysis (HCA), and then the ecstasy tablets were classified into different groups. Cluster analysis of ecstasy tablets is shown to be capable of providing intelligence on clandestine laboratory networks.
RESUMO
The indenylruthenium hydride complex (eta(5)-C(9)H(7))Ru(dppm)H was found to be active in catalyzing the hydration of nitriles to amides. The chloro analogue (eta(5)-C(9)H(7))Ru(dppm)Cl was, however, found to be inactive. Density functional theory calculations at the B3LYP level provide explanations for the effectiveness of the hydride complex and the ineffectiveness of the chloro complex in the catalysis. It is learned that the presence of a Ru-H.H-OH dihydrogen-bonding interaction in the transition state lowers the reaction barrier in the case of (eta(5)-C(9)H(7))Ru(dppm)H, but in the chloro system, the corresponding transition state does not contain this type of interaction and the reaction barrier is much higher. A similar dihydrogen-bond-promoting effect is believed to be responsible for the catalytic activity of the hydrotris(pyrazolyl)borato (Tp) ruthenium complex TpRu(PPh(3))(CH(3)CN)H in CH(3)CN hydration. The chloro analogue TpRu(PPh(3))(CH(3)CN)Cl shows no catalytic activity.
