New extraction method for the analysis of linear alkylbenzene sulfonates in marine organisms. Pressurized liquid extraction versus Soxhlet extraction

A new method has been developed for the determination of linear alkylbenzene sulfonates (LAS) from various marine organisms, and compared with Soxhlet extraction. The technique applied includes the use of pressurized liquid extraction (PLE) for the extraction stage, preconcentration of the samples, purification by solid-phase extraction (SPE) and analysis by liquid chromatography with fluorescence detection. The spiked concentrations were added to the samples (wet mass of the organisms: Solea senegalensis and Ruditapes semidecussatus), which were homogenized and agitated continuously for 25 h. The samples were extracted by pressurized hot solvent extraction using two different extraction temperatures (100 and 150 degrees C) and by traditional Soxhlet extraction. The best recoveries were obtained employing pressurized hot solvent extraction at 100 degrees C and varied in the range from 66.1 to 101.3% with a standard deviation of between 2 and 13. Detection limit was between 5 and 15 microg kg(-1) wet mass using HPLC-fluorescence detection. The analytical method developed in this paper has been applied for LAS determination in samples from a Flow-through exposure system with the objective of measuring the bioconcentration of this surfactant.     

Iodine catalyzed efficient synthesis of symmetrical diaryl sulfoxides from arenes and thionyl chloride under solvent-free conditions

Synthesis of symmetrical diaryl sulfoxides from arenes and thionyl chloride in the presence of a catalytic amount of iodine at room temperature under solvent-free conditions is described.Mild reaction conditions,easy workup,high yield,and easily available catalyst are important features of this method.     

Preparation and characterization of dealuminated metakaolin and its use in the transformation of waste plastics to aromatic hydrocarbons

Acid activated metakaolins (AAMKs) have been prepared by calcination of the natural clay at 600 degrees C to provide a metakolin which was then leached at 80 degrees C for 3 h using 1M, 2M, 3M, and 6M HCl. These materials were characterized and their ability to transform the off gases from HDPE decomposition into useful aromatic species was evaluated. The amount of adsorbed water and the number of acid sites increased with the severity of acid treatment. Variable temperature DRIFTS spectroscopy of pyridine treated samples revealed that both Br?nsted and Lewis acid centers were present until 425 degrees C. Pyridine bonded to the Lewis acid centers was more thermally stable. The AAMKs were all selective to the production of toluene with respectable, but lesser, amounts of xylenes and trimethylbenzenes. This selectivity contrasts with that of acid leached and pillared smectites which are selective toward trimethylbenzene.     

Photochemical expulsion of the neutral monodentate ligand L in Ru(terpy*)(diimine)(L)2+: a dramatic effect of the steric properties of the spectator diimine ligand

A series of photoreactive complexes of the type Ru(terpy*)(N-N)(L)(2+), where terpy* is 4'-(3,5-ditertiobutylphenyl)-2,2':6',2' '-terpyridine, N-N is the bidentate chelate phen or dmp (phen = 1,10-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline), and L is the monodentate ligand dms, MeBN, or MeOBN (dms = dimethyl sulfide, MeBN = 2,6-dimethyl benzonitrile, MeOBN = 2,6-dimethoxybenzonitrile), has been synthesized and fully characterized by proton NMR spectroscopy, electrospray mass spectrometry, and UV-vis spectroscopy. The X-ray structures of four complexes were also obtained. In neat pyridine, the quantum yields for the photosubsitution of L by pyridine were measured and showed dramatic variations depending on the steric interactions between the spectator bidentate ligand and the leaving monodentate ligand L. The use of dmp instead of phen multiplied the photosubstitution efficiency by a factor of 20-50, depending on L. This effect could be qualitatively correlated to the distortions observed in the X-ray structures of the corresponding complexes. The highly distorted structure of Ru(terpy)(dmp)(dms)(PF(6))(2) showed a very high photosubsitution quantum yield phi = 0.36 in neat pyridine. The high photoreactivity of some of the compounds makes them particularly promising as components of future light-driven molecular machines.     

Human insulin and desamido human insulin isotherms in ethanol-water reversed phase systems

The multi-component isotherms for human insulin (HI) and desamido human insulin (dHI) over reversed phase packing (C18) and with 29.8% (w/w) ethanol-water as mobile phase have been determined experimentally. The isotherms of HI in ethanol-water differ from those obtained with the more commonly applied methanol-water and acetonitrile-water mobile phase, as described in this paper. The isotherm exhibits anti Langmuirian behavior and can be very well modeled by an anti Langmuir isotherm presented in this paper. The HI and dHI anti Langmuir isotherm are determined as: qHI = (8.4C(HI) + 3C(HI)CdHI)/(1 - 0.05C(HI) - 0.14CdHI + 0.04C(HI)CdHI) and qdHI = (11.4CdHI + 2C(HI)CdHI)/ (1 - 0.05C(HI) - 0.14CdHI + 0.04C(HI)CdHI)     

简单液体比重计的制法

E.H.费道诺娃叙述了一种适合于学生实验室工作的简单液体比重计的制法。几小时就可做成10—15个。可引导高年级学生来作这项工作。为此目的,需要下列器材:1)直径2厘米,长15厘米的试管;2)筛过的细砂;3)刻度用的白釉料;4)5只量筒;5)电池玻杯;6)蒸馏水;7)天平和砝码;8)食盐和糖;9)汽油焊灯或瓦斯灯(焊接喷灯)。     

天花粉蛋白2.6分辨率的晶体学修正

本文报道了用溶剂过滤法改善电子密度图,依据Collins提出的一级结构,重新建立天花粉蛋白分子模型。使用2.6分辨率衍射强度数据和约束参数最小二乘法,对处于晶体学不对称单元中两个天花粉蛋白分子(共3828个非氢原子)进行晶体学修正。修正结果,偏离因子R=0.223,键长根均方误差r.m.s=0.023,新的分子模型和以2F_0-F_o为系数的电子密度图符合甚好。     

Microchannel-assisted thermal-lens spectrometry for microchip analysis

We present a new method for homocysteine quantitation in human plasma based on in-capillary reaction of homocysteine with 2,2′-dipyridyl disulfide. Homocysteine is in this so-called thiol-exchange reaction quantitatively transformed in mixed disulfide concomitantly with formation of an equimolar amount of 2-thiopyridone that is further separated by micellar electrokinetic chromatography and determined specifically at 343 nm. The concentration of homocysteine is thus estimated indirectly from the result of 2-thiopyridone determination. The linear detection range for concentration versus peak area for the assay was from 0.03–3 mM (correlation coefficient 0.994) with a detection limit of 6 μM and a limit of quantitation 20 μM. The inter-day reproducibility of the peak area and the migration time were 1.37% and 0.05%, respectively. The method is simple, relatively rapid and can be easily automated. Moreover the common capillary electrophoresis apparatus with a UV detector can be used to distinguish between normal and pathological hyperhomocysteinemia plasma samples.     

Capillary electrophoresis analysis of gentamicin sulphate with UV detection after pre-capillary derivatization with 1,2-phthalic dicarboxaldehyde and mercaptoacetic acid

A selective, sensitive, and rapid pre-capillary derivatization method for determination of the multicomponent aminoglycoside antibiotic gentamicin is described. The derivatization reagents 1,2-phthalic dicarboxaldehyde and mercaptoacetic acid were used and the thioisoindole derivative was UV detected at 330 nm. A central composite experimental design was performed to optimize selectivity and derivatization conditions. Baseline separation of gentamicin C1, C1a, C2, C2a, C2b, sisomicin and several minor components was achieved with a background electrolyte containing 30 mM sodium tetraborate, 7.5 mM beta-cyclodextrin and 12.5% (v/v) methanol at pH 10. Quantitative analysis was performed and illustrated the potential use of capillary electrophoresis for the identification and quantitation of gentamicin as an alternative to methods prescribed in the United States Pharmacopeia and European Pharmacopoeia.