Statistical validation is crucial for the clustering of unknown samples. This study aims to demonstrate how statistical techniques can be optimized using simulated heroin samples containing a range of analyte concentrations that are similar to those of the case samples. Eight simulated heroin distribution links consisting of 64 postcut samples were prepared by mixing one of two mixtures of paracetamol-caffeine-dextromethorphan at different proportions with eight precut samples. Analyte contents and compositional variation of the prepared samples were investigated. A number of data pretreatments were evaluated by associating the postcut samples with the corresponding precut samples using principal component analysis and discriminant analysis. Subsequently, combinations of seven linkage methods and five distance measures were explored using hierarchical cluster analysis. In this study, Ward-Manhattan showed better distinctions between unrelated links and was able to cluster all related samples in very close distance under the known links on a dendogram. A similar discriminative outcome was also achieved by 90 unknown case samples when clustered via Ward-Manhattan.
In the title co-crystal, [Mo(C(14)H(9)ClN(2)O(4))O(2)(CH(3)OH)]·C(10)H(8)N(2), the deprotonated Schiff base O,N,O'-chelates to the Mo(VI) atom, the three atoms involved in chelation comprising the fac sites of the octa-hedron surrounding the methanol-coordinated metal atom. The methanol mol-ecule forms an O-H⋯N hydrogen bond to an N atom of the 4,4'-bipyridine solvent mol-ecule; the hy-droxy group of the Schiff base forms an O-H⋯N hydrogen bond to the other N atom of another mol-ecule. The two hydrogen bonds leading to the formation of a helical chain running along the b axis.
The Mo(VI) atom in the title co-crystal, [Mo(C(14)H(12)N(2)O(4))O(2)(H(2)O)]·0.5C(10)H(8)N(2), is O,N,O'-chelated by the deprotonated Schiff base and coordinated by the oxide and water O atoms in an octa-hedral geometry. The five-membered chelate ring is planar (r.m.s. deviation = 0.019 Å), but the six-membered chelate ring is puckered (r.m.s. deviation = 0.108 Å). Two mononuclear mol-ecules are linked across a center of inversion by an O-H(water)⋯O hydrogen bond; adjacent dinuclear units are linked by an water-4,4'-bipyridine O-H⋯N hydrogen bond, generating a linear chain structure. The 4,4'-bipyridine mol-ecule is disordered over two positions in a 1:1 ratio.
The asymmetric unit of the title compound, [Mo(2)(C(5)H(5))(2)(C(7)H(7)S)(2)(CO)(2)], consists of two half-mol-ecules, each molecule lying on a centre of symmetry. The thiol-ate groups function as bridges between the Mo(II) atoms, which adopt a quasi-octa-hedral geometry. In the octa-hedral environment the two ligating S atoms are in a cis arrangement.
Apart from routine analysis of total morphine content required by the criminal justice system, quantification of other major components in illicit heroin has not been considered by the Malaysian enforcement laboratory. In order to quantify various other cutting agents in addition to alkaloids, a gas chromatographic (GC) method was developed to facilitate simultaneous quantification of eight target analytes commonly found in illicit heroin seized in Malaysia within a 12 min run time. The validation results demonstrated high selectivity with the use of an HP Ultra 2 capillary column. Different solvents were studied and methanol:chloroform (1:9) proved best for sample dissolution. The method was repeatable and reproducible. The study ranges covering 50-150% of the preferred concentrations of the eight analytes obtained r(2)>0.9997. Limits of detection up to 6μg/mL were also obtained and the method achieved 99-102% recovery. The capability of the method in heroin profiling was verified using samples from ten case samples.
Sixteen trace elements found in 309 street heroin samples, piped water and contaminated water were determined using inductively coupled plasma-mass spectrometry. All the street heroin samples were found to contain high levels of sodium, a reflection of the use of sodium bicarbonate during heroin synthesis. Additionally, this element was also found to be one of the potential contaminants acquired from the piped water. Calcium could be derived from lime while iron, aluminum and zinc could have come from the metallic container used in the processing/cutting stage. The levels of these elements remained low in the heroin and it could be due to the dilution effects from the addition of adulterants. Statistical validation was performed with six links of related heroin samples using principal component analysis to find the best pretreatment for sample classification. It was obtained that normalization followed by fourth root showed promising results with 8% errors in the sample clustering. The technique was then applied to the case samples. Finally, the result suggested that the case samples could have originated from at least two major groups respectively showing unique elemental profiles at the street level.
Statistical classification remains the most useful statistical tool for forensic chemists to assess the relationships between samples. Many clustering techniques such as principal component analysis and hierarchical cluster analysis have been employed to analyze chemical data for pattern recognition. Due to the feeble foundation of this statistics knowledge among novice drug chemists, a tetrahedron method was designed to simulate how advanced chemometrics operates. In this paper, the development of the graphical tetrahedron and computational matrices derived from the possible tetrahedrons are discussed. The tetrahedron method was applied to four selected parameters obtained from nine illicit heroin samples. Pattern analysis and mathematical computation of the differences in areas for assessing the dissimilarity between the nine tetrahedrons were found to be user-convenient and straightforward for novice cluster analysts.