Analysis of gasoline contaminated water samples by means of dopant-assisted atmospheric pressure photoionization differential ion mobility spectrometry

In this study the influence of aromatic dopant benzene on the sensitivity of GC-APPI-DMS to gasoline related aromatic compounds was investigated. This influence was investigated on example of four gasolin related fingerprints (toluene, ethylbenzene, o-xylene, and 1,2,4-trimethylbenzene), which were found in high relative abundance in the water-soluble gasoline fraction. The analysis of calibration curves slopes demonstrats that the GC-APPI-DMS sensitivity to gasoline fingerprints can be improved by up to seven times when benzene concentration in nitrogen carrier gas is less than 10 ppm_v/v. The estimated detection limits (S/N?=?3) for the analyzed in this study compounds were found to be within the range of 33–105 μg L^?1 at benzene concentration in the carrier gas of 2.27 ppm_v/v (10 μL injection volume). These limits of detection may be reduced (at the cost of lower resolution) using the larger injection volumes. For example, increase of injection volume to 100 μL at benzene concentration in the carrier gas of 2.27 ppm_v/v leads to reduction of LOD values for toluene, ethylbenzene, and o-xylene to 11.1, 13.3, and 5.3 μg L^?1, respectively.     

Strong base induced cycloaddition of 3-carboxy-1-methylindole-2-acetic anhydride and 2-carboxybenzo[b]furan-3-acetic anhydride: synthesis of polycyclic peri-hydroxylated indole and benzofuran compounds

Generation of indole- and benzofuran-2,3-orthoquinodimethane-like intermediates is described. The cycloaddition reaction of these intermediates to dienophiles provided an efficient one-pot synthesis of polycyclic perihydroxylated indole and benzofuran compounds.     

On rational integrability of Euler equations on Lie algebra so(4, ℂ)

We consider the Euler equations on the Lie algebra so(4, ℂ) with a diagonal quadratic Hamiltonian. It is known that this system always admits three functionally independent polynomial first integrals. We prove that if the system has a rational first integral functionally independent of the known three ones so called fourth integral, then it has a polynomial first integral that is also functionally independent of them. This is a consequence of more general fact that for these systems the existence of Darboux polynomial with no vanishing cofactor implies the existence of polynomial fourth integral.     

A short and efficient synthesis of 11-deoxyanthracyclinones: strong base-induced cycloaddition of the suitably substituted tetrahydrohomophthalic anhydride

The preparation and use of the suitably substituted tetrahydrohomophthalic anhydride ($\text{17}$) as a common intermediate for a short regiospecific synthesis of 11-deoxyanthracyclinones, 11-deoxydaunomycinone ($\text{11}$), 11-deoxy-carminomycinone ($\text{12}$), and 4-demethoxy-11-deoxydaunomycinone ($\text{13}$) is described.     

Synthetic anthracyclines: regiospecific total synthesis of D-ring thiophene analogues of daunomycin

The key anhydride 2-acetoxy-[2-carboxy-5-(trimethylsilyl)thiophen-3-yl]acetic acid anhydride (8), prepared from (2-carboxythiophen-3-yl)acetic acid (5), underwent a strong base-induced cycloaddition reaction with the chloroquinone acetal (11) to give the 7,7-ethylenedioxy-2-trimethylsilyl-6,7,8,9- tetrahydroanthra[2,3-b]thiophene-5,10-dione (12) regioselectively. Similarly, the regioisomeric 8,8-ethylenedioxy-2-trimethylsilyl-6,7,8,9-tetrahydroanthra[2,3-b] thiophene- 5,10-dione (30) was obtained by the strong base-induced cycloaddition reaction of 8 with the chloroquinone acetal (29). These cycloadducts (12 and 30) were converted to D-ring thiophene analogues (28 and 38) of daunomycin (1a). Another D-ring thiophene analogue (42) which has a trimethylsilyl substituent in the D-ring was also prepared.     

Cuprous sulfide deposition method for visualization of latent fingermarks on unfired cartridge cases

A new chemical method for visualization of latent fingermarks on unfired cartridge cases is reported in this research. The method is based on two-step immersion of the cartridge cases in aqueous solutions of sulfuric acid and acidified sodium thiosulfate at room temperature. The chemical reactions that are occurring on the cartridge case's surface are leading to deposition of material in the furrows between the papillary line ridges thus visualizing the latent fingermark. The qualitative chemical composition of the as-deposited material was studied using X-ray powder diffraction analysis thus revealing that it corresponds to a low-crystalline hexagonal chalcocite phase cuprous sulfide (Cu₂S). The performance of the method was studied on fresh and aged fingermarks, and according to the results, it can visualize latent fingermarks that are up to 9 months old. The newly proposed method provides good performance considering the most important qualitative and quantitative parameters that describe each fingermark, that is, satisfactory contrast between the papillary line ridges and the background furrows, possibility of recognizing the pattern of each fingermark (arch, loop, and whorl), clarity and continuity of the friction ridges, and clarity of the second level characteristics and features. The proposed method is simple, fast, inexpensive, and reliable.     

Microwave-assisted and conventional sol-gel preparation of photocatalytically active ZnO/TiO2/glass multilayers

For the first time a combination of microwaves and/or the conventional treatment method was used to dry and heat multilayered sol-gel ZnO/TiO₂/glass structures. Compact or porous TiO₂ films were deposited as a bottom layer, covered with a ZnO film. The structures were characterized by X-ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDX) and Scanning Electron Microscopy (SEM). Only peaks of wurtzite ZnO crystalline phase were registered on the X-Ray diffractograms. The microwave irradiation leads to a formation of poorly crystallized multilayers with very small crystallites and enhanced surface roughness. This results in a better photocatalytic activity of these structures than the structures of the samples treated conventionally. It was established that the morphology of the bottom titania layer affects the reaction of photocatalytic degradation of Malachite Green dye (MG). The structures with the compact bottom TiO₂ films showed higher activities than those on porous TiO₂ films. This study offers an energy saving method of producing ZnO/TiO₂/glass multilayered structures of various morphologies and pronounced photocatalytic properties. The method does not involve any calcination step, normally applied to achieve a good degree of crystallization. This makes the method suitable for protecting substrates of low thermal stability.      

Tautomerism of rhodanine

Semiempirical (MINDO/3, AM1, PM3, MNDO) and ab initio (4-31G and 4-3IG + dAO/S basis sets) calculations on the relative stabilities and structures of the five potential tautomeric forms of rhodanine are reported. It is shown that all methods (excepting PM3) predict as most stable 2-thioxo-4-thiazolidinone. These results correspond to the known experimental data. The infrared spectrum of rhodanine was recorded for the region 4000-150 cm^–1, and the characteristic bands were compared with AM1 and 4-31G + dAO/S calculated frequencies. The transition states between five pairs of all possible tautomeric forms of the rhodanine were found by the AM1 method.