This paper seeks to evaluate whether the chemical profiling data obtained with a constant weight approach can be used in the classification of highly cut heroin samples. A constant weight of a seized ...substance instead of the conventional weight equivalent to 15 mg heroin base was used to profile the manufacturing impurities. The study attempts to optimize four clustering tools using 12 impurity peaks extracted from the heroin samples (<2.3% purity) analyzed at 650 mg sample weight to find the most ideal statistical techniques for sample classification. The effectiveness of four clustering tools, namely the principal component analysis (PCA), hierarchical cluster analysis (HCA), K-means clustering (KMC) and discriminant analysis (DA) was assessed using 25 heroin samples derived from five known batches. HCA and DA proved promising in clustering the related samples. Finally, only the HCA was then employed to evaluate the general relationships between 46 unknown heroin samples.
Related organic impurities generally have approximately similar molar absorption coefficients (
ɛ) due to their structural similarities. On the assumption that all peaks in an impurity profiling ...chromatogram have approximately the same maximum molar absorption coefficients (
ɛ
max) and the chromatogram contains one major peak and several much smaller ones, all of which are completely separated, integration of the summed score vectors from the principal component analysis (PCA) decomposition of high-performance liquid chromatography–diode array detection (HPLC–DAD) data will give areas that are quantitatively proportional to the actual content of the compounds. Due to the sequential nature of PCA, the first principal component (PC) will primarily be related to the main compound and all peaks showing a similar spectrum, while the second PC will be related to the impurities with a spectrum different from the main peak. Summing the two score vectors thus makes it possible to take account of different spectra in the score chromatogram, which make the method proposed give better quantitative estimates of the impurities than any single wavelength chromatogram. Multivariate curve resolution alternating least squares (MCR-ALS) is used for comparison. The results are presented for two examples of simulated HPLC–DAD data as well as for three examples of real HPLC–DAD data from impurity profiling. The results show that integration of the score chromatograms can handle differences in the unknown
ɛ
max of the peaks and take account of the different spectra of the impurity peaks, giving quantitative estimates of the content of the impurities that closely correspond to the reference values. The results obtained are also better than integration with the best possible separate wavelength. The method could be a straightforward approach to impurity profiling in order to obtain a good estimate of the content or relative response factors of small chromatographic impurity peaks without knowledge of their molar absorption coefficients and without any precalibration.
The thermocapillary convection (TC) induced by a laser beam on thin aqueous layers placed on an absorbing non-heat-conducting substrate is experimentally investigated. It is shown that after a lag ...time after turning on of a laser beam the presence of TC is registered by a sharp splash, after which the TC response grows to its steady-state value.
The deviation of the duration of this pause from its quadratic variation with thickness of the liquid layer depending on the degree of organic impurity of water is another important experimental result. The above results can serve as a basis for development of a method for measuring the thermal diffusivity of liquids and for monitoring water purity.
A new approach to the removal of organic impurities from the technological aluminate solution of alumina production via processing the solution by a high-speed oxidizing thermal-plasma jet flowing ...into the solution bulk is considered. It is experimentally shown that, during the plasma treatment of aqueous solutions of phenol and humic acids, a degree of the transformation of starting organic compounds exceeding 80% is achieved. In experiments on the plasma treatment of the technological solution, a decrease in the chemical consumption of oxygen by more than 60% is achieved, which indicates a considerable decrease in the concentration of organic impurities.
Analysis of gas chromatography-mass spectrometry and IR spectrometry shows that the composition of organic impurities in stream and water bodies of the Tom’ basin depends on natural and anthropogenic ...factors. The anthropogenic load is especially important, as the organic impurities originating from oil (paraffins, isoparaffins, naphthenes, aromatic hydrocarbons) are predominant; other pollutants of anthropogenic origin are also present (phthalates, carboxylic acids and their esters, phosphates). The composition of organic pollutants dumped into the river from each industrial zone has been analyzed both qualitatively and quantitatively.
The electrowinning (EW) of cobalt from sulphate solution contaminated with organic impurities: tri-
n-butyl phosphate (TBP), 2-hexylmethyl decanoic acid (VERSATIC 10), 2-hydroxy-5-nonyl acetophenone ...oxime (LIX 84), di-2-ethylhexyl phosphoric acid (D2EHPA) and di-2,4,4-trimethylpentyl phosphinic acid (CYANEX 272) has been investigated at 60 °C. Both cyclic voltammetry and flow cell electrolysis have been used. The effect of organic impurities on the cathodic reduction of cobalt is compared with the blank solution. The current efficiency is more than 90% in most cases and is highest in the case of D2EHPA (96%) and lowest with VERSATIC 10 (86%). The cathodic polarization from cyclic voltammetry indicates that the exchange current density (
i
0) value is higher in the presence of organic impurities than in solutions containing no organic impurities. The organic impurities indicate an inhibition of electrocrystallization process due to suppression of nucleation. Cathodic polarization also indicates that Co
2+ reduction occurs slightly at less negative potential in solution containing organic impurities.
The reuse of
18O water after being purified by distillation has been reported to give lower
18F2-fluoro-2-deoxy-
d-glucose (
18FFDG) yields, probably due to the presence of organic impurities. In ...our routine production of
18FFDG, however, we observed increased
18FFDG yields with recycled
18Owater. Thus, factors affecting
18FFDG yield were examined using as-purchased (virgin) and recycled (by photochemical combustion and distillation)
18Owater.
18FFDG was synthesized by nucleophilic
18F-fluorination on a quaternary 4-aminopyridinium resin. The recycled
18Owater gave an
18FFDG yield significantly higher than did the virgin water, without any significant difference in the
18Ffluoride yield. Levels of several ionic impurities including Cl
− and Ca
2+ were significantly higher in the virgin
18Owater than in the recycled water, while significantly larger amounts of organic impurities were detected in the former. Hence, trace amounts of organic impurities were not responsible for the lower
18FFDG yield. Chloride anion in the
18Owater may compete with
18Ffluoride to lower the
18FFDG yield.
The methods and flow charts used for the industrial preparation of PET are shown and briefly discussed. Then, the three classes of contaminants usually appearing in PET are described and their causes ...elucidated. The organic contaminants impart to the produced PET an undesired yellow-amber tinge while those containing metal ions or elemental metals impart to the polymer various undesirable colors. Other organic contaminants are crosslinked gels and flakes, and especially the latter may cause filament rupture and may lead to the disruption of melt spin-draw processes. Some remedies to eliminate or minimize the appearance of such contaminants are then suggested, followed by a brief discussion of non-antimony catalysts which eliminate the gray discoloration usually imparted to PET by antimony-containing catalysts.
![Increased [ 18F]2-fluoro-2-...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0969-8043/small "Increased [ 18F]2-fluoro-2-deoxy- d-glucose ([ 18F]FDG) yield with recycled target [ 18O]water: factors affecting the [ 18F]FDG yield")
