Solubility of Anthracene in Binary Carbon Tetrachloride + Alkane Solvent Mixtures

Abstract

Experimental solubilities are reported for anthracene in binary solvent mixtures containing carbon tetrachloride with n-hexane, n-heptane, n-octane, cyclohexane, methylcyclohexane and isooctane at 25°C. Results of these measurements, combined with the excess Gibbs free energies of the binary solvents, are used to test predictive expressions derived from the nearly ideal binary solvent (NIBS) model. Expressions based on a volume fraction average of solute properties in the two pure solvents predict anthracene solubilities to within a maximum deviation of 4.5% and an overall average deviation of 1.8%.     

Ternary Liquid-Liquid Equilibria Of (Acetonitrile + n-Octane + Propanols or Butanols)

Abstract

The liquid-liquid equilibria of (acetonitrile + n-octane + 1-propanol or 2-propanol or 1-butanol or 2-butanol, or iso-butanol or tert-butanol) at 298.15 K have been measured. The ternary experimental results agree well with those predicted from the UNIQUAC associated-solution model with binary parameters alone.     

Phase equilibria of binary mixtures containing methyl acetate,water, methanol or ethanol at 101.3 kPa

Isobaric vapor–liquid equilibria data at 101.3?kPa were reported for the binary mixtures (methyl acetate?+?(water or methanol or ethanol), methanol?+?(water or ethanol) and (ethanol?+?water)). The experimental data were tested for thermodynamic consistency by means of the Wisniak method and were demonstrated to be consistent. The experimental data were correlated using Wilson, NRTL and UNIQUAC models for the activity coefficients and predicted using the UNIFAC and PSRK equation of state for testing theirs capability. The results show that the obtained data for the studied binary systems are more reliable than other published data.     

超声辅助提取高效液相色谱法检测小麦籽粒中杀雄嗪酸的残留

建立了高效液相色谱法(HPLC)检测小麦籽粒中化学杂交剂SQ-1主成分杀雄嗪酸残留的方法。以75%乙醇为提取剂,正反萃取净化;采用Diamonsil C18不锈钢柱,以甲醇-0.5%(NH4)2HPO4溶液(60∶40,V/V,pH 2.5)为流动相,检测波长283 nm,流速1.0 mL/min。结果表明:化学杂交剂SQ-1主成分杀雄嗪酸在0.75～25.0 mg/L范围内线性关系良好,相关系数r=0.9999,在3个添加水平(1.0,5.0和10.0 mg/kg)范围内,平均加标回收率在84.2%～95.0%之间,相对标准偏差为1.0%～3.3%,检出限为0.075 mg/L。     

Solution and solid state studies with the bis-oxalato building block [Cr(pyim)(C2O4)2]− [pyim = 2-(2′-pyridyl)imidazole]

The preparation, X-ray structure, and variable temperature magnetic study of the new compound {Ba(H₂O)_3/2[Cr(pyim)(C₂O₄)₂]₂}_n·9/2nH₂O (1) [pyim = 2-(2′-pyridyl)imidazole and C₂O₄^2? = dianion of oxalic acid], together with the potentiometric and spectrophotometric studies of the protonation/deprotonation equilibria of the pyim ligand and the ternary complex [Cr(pyim)(C₂O₄)₂]^?, are reported herein. The crystal structure of 1 consists of neutral chains, with diamond-shaped units sharing barium(II), with the two other corners occupied by chromium(III). The two metal centers are connected through bis(bidentate) oxalate. Very weak antiferromagnetic interactions between the chromium(III) ions occur in 1. The values of the protonation constants of the imidazole and pyridyl fragments of pyim as well as the acidity constant of the coordinated pyim in [Cr(pyim)(C₂O₄)₂]^? are determined for the first time by potentiometry and UV–Vis spectroscopy in aqueous solution (25?°C and 0.15 M NaNO₃ as ionic strength).     

Principal component and Tucker3 analyses of high performance liquid chromatography with diode-array detection fingerprints of crude extracts of Erythrina speciosa Andrews leaves

Mixtures of ethanol, dichloromethane, hexane and acetone obtained according to a statistical design have been used to extract substances from Erythrina speciosa Andrew leaves for chromatographic fingerprinting. The plant extracts from each mixture were analyzed by HPLC-DAD providing UV–vis spectra for each chromatographic peak. These chromatograms and spectra for the design mixtures were then treated with principal component (PCA), Tucker3 and PARAFAC analyses. PCA indicated the existence of five different chromatographic fingerprints for the leave extracts depending on the solvent mixture composition. Different chromatographic peak areas were strongly correlated with the mixture proportions of acetone, dichloromethane and ethanol. Tucker3 and PARAFAC analyses were very useful for identifying simultaneous correlations between chromatographic peak areas, spectral band absorbances and solvent proportions. The acetone proportion was highly correlated with the area of the 3.69 min retention time peak and the spectral absorbances between 250 and 260 nm, consistent with the presence of natural polyphenols. The dichloromethane mixture proportion was strongly correlated with the 12.19 min chromatographic peak area and a single spectral absorbance at 201 nm. This spectral absorption is characteristic of the electronic structures of terpenes and alkaloids.     

Analytical procedures for the determination of emerging organic contaminants in plant material: A review

In this review, recent developments for the determination of emerging organic contaminants (EOCs) in plant tissues are discussed focusing on the homogenization, extraction and determination steps involved. Eleven classes of EOCs, namely antibiotics, analgesics, antiepileptics, antidepressants, antiseptics, plasticizers, fragrances, surfactants, flame retardants, and phenoxy acid herbicides, have been evaluated. Methods are critically reviewed in terms of all the analytical steps involved in the analysis, sampling and sample preparation, separation, and the detection strategies employed. The extraction from tissue samples was performed in most cases by solid–liquid extraction, whereas the clean-up was performed by solid-phase extraction. The identification and quantification of EOCs in crops from the agricultural field (i.e. parts per billion range) is usually performed by using mass spectrometry techniques such as single quadrupole mass spectrometry or tandem mass spectrometry coupled to high resolution chromatographic techniques. Enzyme-linked immunosorbent assays are more rarely used. New developments such as in vivo solid-phase microextraction (SPME) and the assessment of the bioavailability–bioaccesibility of contaminants in crops are shown. The main scope of this review is to critically evaluate the current state of the art of the analytical techniques used and to identify the research needs in the determination of EOCs in crops.     

Identification and Isotopic Analysis of Safranal from Supercritical Fluid Extraction and Alcoholic Extracts of Saffron

Abstract

Saffron is one of the most expensive spices. Consequently, it is not so difficult to understand that fraudulent saffron exists. Thus, it was interesting to study the most important flavouring component, in terms of aroma, volatile compound of saffron - safranal - by ¹³C isotopic analysis. Five saffron samples from different countries have been analysed. Safranal has been extracted by methanol or by Supercritical Fluid Extraction (SFE). The results indicate that there is a significant difference between the synthetic safranal and the natural one. On the contrary, it is difficult to conclude on the difference between the various geographical origins, as the isotopic variations are small. Moreover, it has been found that Supercritical Fluid Extraction allowed the selective extraction of volatile compounds from saffron under optimised conditions. It is a cleaner and faster method of extraction compared to the extraction using organic solvent. Nevertheless, an isotopic fractionation occurs in relation to the extraction yield of safranal.     

Extraction of Ce(III), Gd(III) and Yb(III) from Citrate Medium by High Molecular Weight Amines

Abstract

High molecular weight amines have been used for the extraction of citrate complexes of Ce(III), Gd(III) and Yb(III). The effect of different variables on extraction has been studied. The citrate species extracted in the organic phase have been proposed as [(RNH₃ ⁺)₃] [M(Cit)₂]^3-.     

Analysis of Geting Bituminous Coal by Electrospray Ionization and Direct Analysis in Real Time Mass Spectrometry

Understanding the structure and composition of coals is important for effective, clean, and value-added utilization. In addition to gas chromatography/mass spectrometry which is commonly used to analyze coal, mass spectrometry (MS) may be used with other ion sources such as electrospray ionization (ESI) and direct analysis in real time (DART) for characterization. In this work, Geting bituminous coal was extracted sequentially and exhaustively with petroleum ether, carbon disulfide, methanol, acetone, an isometric acetone/carbon disulfide mixture, tetrahydrofuran, and an isometric tetrahydrofuran/carbon disulfide mixture. Raw coal, extracts, and the extraction residue were analyzed using MS equipped with ESI or DART. Organic heteroatomic species in the extracts were determined by liquid chromatography-mass spectrometry equipped with ESI. Molecular weight distributions of organic species in raw coal, extracts, and extraction residue were characterized by ESI-MS and DART-MS. Associated molecules and homologous compounds in coal extracts were identified.