The Determination of Sulfur and Chlorine in Coals and Oil Shales Using Ion Chromatography

Abstract

The determination of sulfur and chlorine in coal and oil shale standards is reported. The procedure utilizes a sample decomposition using Eschka's mixture, followed by an ion chromatographic determination. The method was tested on samples with concentrations ranging from 0.004 to 0.35 percent chlorine and 0.05 to 4.4 percent sulfur. Results compare favorably with values reported in the literature. The detection limits for chlorine and sulfur were 10 and 13 ppm and the precision of the method expressed as a percent relative standard deviation was 6 percent and 5 percent for chlorine and sulfur respectively. Using this method a single operator can prepare and analyze as many as 30 samples per day.     

Reverse microemulsion-mediated synthesis of silica-coated gold and silver nanoparticles

A reverse microemulsion method is reported for preparing monodispersed silica-coated gold (or silver) nanoparticles without the use of a silane coupling agent or polymer as the surface primer. This method enables a fine control of the silica shell thickness with nanometer precision. As compared to the St?ber method reported for direct silica coating, which can only coat large gold particles ( approximately 50 nm in diameter) at low concentrations (<1.5 x 10(10) particles/mL), this new approach is capable of coating gold particles of a wide range of sizes (from 10 to 50 nm) at a much higher concentration ( approximately 1.5 x 10(13) particles/mL). Moreover, it enables straightforward surface functionalization via co-condensation between tetraethyl orthosilicate and another silane with the desired functional groups. The functional groups introduced by this method are readily accessible and thus useful for various applications.     

细菌修饰的碳糊电极表面超细微粒金膜的制备及应用

本文提出一种采用电化学方法在巨大芽孢杆菌Ｄ０１修饰的碳糊电极表面制备超细微粒金膜的新方法,获得由平均粒径为８０ｎｍ金微粒组成的金膜。该方法操作简单,耗金量少,以此金膜作为工作电极检测水溶液中痕量铜具有良好的重现性和线性,检测灵敏度达０．０２ｎｇ／ｍＬ,该电极既可象金片电极多次反复被使用,也可以象碳糊电极一样不断更新表面。     

Comparison study of two procedures for the determination of emamectin benzoate in medicated fish feed

A new method has been developed for the determination of emamectin benzoate in fish feed. The method uses a wet extraction, cleanup by solid-phase extraction, and quantitation and separation by liquid chromatography (LC). In this paper, we compare the performance of this method with that of a previously reported LC assay for the determination of emamectin benzoate in fish feed. Although similar to the previous method, the new procedure uses a different sample pretreatment, wet extraction, and quantitation method. The performance of the new method was compared with that of the previously reported method by analyses of 22 medicated feed samples from various commercial sources. A comparison of the results presented here reveals slightly lower assay values obtained with the new method. Although a paired sample t-test indicates the difference in results is significant, this difference is within the method precision of either procedure.     

ICP-MS法快速测定丙烯腈/乙腈中的铁、铜

采用带八级杆碰撞/反应池(ORS)的电感耦合等离子体质谱法(ICP-MS),直接测定丙烯腈或乙腈产品中的Fe、Cu,标准加入法定量.结果表明,方法的线性范围宽,线性相关系数均大于0.999.2种元素的相对标准偏差均低于5%,加标回收率在90%~110%.该方法简便、快速、准确.     

噻吩基和呋喃基取代的1,2,3-硒二唑衍生物的合成

提供了一种合成噻吩基和呋喃基取代的衍生物的方法,并用其合成方法合成了四种未见文献报道的化合物,测定了四种化合物的红外光谱,核磁共振及元素分析值。     

Optimization and characterization of a sulfate based electrodeposition method for alpha-spectrometry of neptunium and curium

The parameters for a sulfate based electrodeposition method were optimized for the preparation of Cm and Np alpha-spectrometry sources. Alpha-spectrometry requires the preparation of essentially massless sources to eliminate self-absorption of alpha-particles, which can cause degraded alpha-spectra. A variety of methods for the electrodeposition of actinides have been reported in the literature, many of which require long deposition times and lack reproducibility. A previously reported sulfate based method has been evaluated for the preparation of Np and Cm sources. High yields were achieved and source preparation took 90 minutes or less. The effects of electrodeposition time and pH of the depositing solution were evaluated for each element. Typical resolution (FWHM) for sources prepared by this method is 50 keV or less with recoveries approaching 100%.     

In situ functionalization of porous silicon during the electrochemical formation process in ethanoic hydrofluoric acid solution

In this work, the results of a new method for the preparation of porous silicon (PS) layers with in situ simultaneous functionalization with organic molecules are reported. The molecules of interest are dissolved in the HF ethanoic solution used to prepare the PS layers by partial anodic dissolution of a Si electrode. The method has been proved to be effective with various molecules. In this Communication, the case of PS functionalization with heptyne molecules, studied by FTIR spectroscopy, is reported in detail. The results demonstrate that this new functionalization method, accompanied by a low-level oxidation, is simple, fast, and effective and that it can allow the confinement of the adsorbed molecules selectively in a single layer of a PS stack.     

Selecting effective siRNA sequences based on the self-organizing map and statistical techniques

Short interfering RNA (siRNA) has been widely used for studying gene functions in mammalian cells but varies markedly in its gene-silencing efficacy. Although many design rules/guidelines for effective siRNAs based on various criteria have been reported recently, there are only a few consistencies among them. This makes it difficult to select effective siRNA sequences in mammalian genes. Here, we propose a new method for selecting effective siRNA target sequences on the basis of the self-organizing map (SOM) technique and statistical significance analyses for a large number of effective siRNAs. In the proposed method, the score is defined as a gene degradation measure. The effectiveness for the proposed method was confirmed by evaluating effective and ineffective siRNAs for recently reported genes (12 genes, 172 siRNA sequences) and comparing with other reported scoring methods. The size (value) of this score is closely correlated with the degree of gene degradation, and the score can easily be used for selecting high-potential siRNA candidates. The evaluation results indicate that the proposed method would be useful for many other genes. It will therefore be useful for selecting siRNA sequences in mammalian genes.     

Nickel-catalyzed amination of aryl sulfamates and carbamates using an air-stable precatalyst

A facile nickel-catalyzed method to achieve the amination of synthetically useful aryl sulfamates and carbamates is reported. Contrary to most Ni-catalyzed amination reactions, this user-friendly approach relies on an air-stable Ni(II) precatalyst, which, when employed with a mild reducing agent, efficiently delivers aminated products in good to excellent yields. The scope of the method is broad with respect to both coupling partners and includes heterocyclic substrates.     

Rapid measurement of oestradiol and oestriol by high-performance liquid chromatography after automatic pretreatment

A fluorometric liquid chromatographic method was developed for measurements of unconjugated oestradiol and oestriol in the serum of pregnant women. The serum samples are injected directly into the apparatus and pass to a pretreatment column, where oestrogens are adsorbed while hydrophilic components such as proteins and carbohydrates are not. The oestrogens then pass into a separation column containing a new type of polymer gel. The mobile phase consists of an acetonitrile-water mixture, and separation is achieved by a reversed-phase mechanism. The eluent is monitored for fluorescence. Data on the reproducibility and recovery by this method and the correlation of values with those obtained by radioimmunoassay are reported. Results on the increases of oestradiol and oestriol in the serum during pregnancy are also reported.     

Efficient catalytic enantioselective synthesis of unsaturated amines: preparation of small- and medium-ring cyclic amines through mo-catalyzed asymmetric ring-closing metathesis in the absence of solvent

The first catalytic asymmetric ring-closing metathesis method for the synthesis of N-containing heterocycles is reported; this is accomplished through Mo-catalyzed kinetic resolution or desymmetrization of unsaturated amines. Importantly, this catalytic asymmetric method delivers medium-ring unsaturated amines (including eight-membered rings) in high yield, with exceptional enantioselectivity and without the need for solvents. These enantioselective reactions can be effected by catalysts prepared in situ from commercially available reagents.     

Efficient conversion of primary and secondary alcohols to primary amines

A convenient single-vessel conversion of primary and secondary alcohols to primary amines is reported. Use of this method results in substantially cleaner crude products than similar procedures reported in the literature. A simple work-up also makes this procedure ideal for parallel synthesis.     

Fast and highly efficient solid state oxidation of thiols

A fast and efficient solid state method for the chemoselective room temperature oxidative coupling of thiols to afford their corresponding disulfides using inexpensive and readily available moist sodium periodate as the reagent is described. The reaction was applicable to a variety of thiols giving high yields after short reaction times. Comparison of yield/time ratios of this method with some of those reported in the literature shows the superiority of this reagent over others under these conditions.     

基于亚甲基蓝的水体急性毒性快速检测方法研究

水体急性毒性的快速检测对保障用水安全至关重要。本研究以荧光假单胞菌为毒性检测的受试体,以细胞膜受损为毒性响应机理,建立了一种新颖的基于亚甲基蓝的水体急性毒性快速检测方法。在本方法中,亚甲基蓝可以对细胞膜受损的细胞进行染色,而不能对细胞膜结构完整的细胞进行染色,因此,当有毒性物质存在并对细胞膜产生破坏时,溶液中的亚甲基蓝会进入细胞对细胞进行染色,从而降低溶液中的亚甲基蓝浓度。通过光谱法检测溶液中亚甲基蓝浓度的变化,就可以实现对水体急性毒性的快速检测。实验结果表明,本方法对3,5-二氯苯酚(DCP)、As3+和Hg2+的最低响应浓度分别为1.6,12.5和3.2 mg/L,对DCP的最低响应浓度比商业化仪器Baroxymeter低。本方法操作简单,检测快速,结果可靠,在水体急性毒性的检测和监测领域具有很好的应用前景。     

A Convenient Synthesis of Aromatic-Ring-Substituted Diacetylenes

A simple and convenient way for the preparation of symmetrical diarylbutadiynes 5 with improved yields is reported (Scheme 2). The reaction time is drastically reduced using this method compared to previously reported procedures.     

Stereocontrol in a combined allylic azide rearrangement and intramolecular Schmidt reaction

Pre-equilibration of an interconverting set of isomeric allylic azides is coupled with an intramolecular Schmidt reaction to afford substituted lactams stereoselectively. The effect of substitution and a preliminary mechanistic study are reported. The synthetic potential of this method is demonstrated in the context of an enantioselective synthesis of an advanced intermediate leading toward pinnaic acid.     

Determination of chemical composition of solid inorganic substances and materials using the principles of stoichiography and voltammetry

The state of the art in determination of the phase composition of complex inorganic solids by chemical and electrochemical methods is discussed. The theoretical and practical essentials of stoichiography and the new stoichiographic method of differential dissolution (DD) are reported. The unique feature of this method is that reference samples of the analyzed solid phases are not necessary. The development of this stoichiographic method was strongly affected by voltammetry. The application of the DD method for determining the chemical composition of various substances and materials is presented. The complementary use of voltammetry and DD for the detection, identification, and quantitative determination of inhomogeneity of the chemical composition of high-temperature superconductors was shown to be efficient.     

The determination of nicotine and cotinine by ion pair reversed-phase chromatography

An ion chromatographic method is described for the determination of nicotine and cotinine in aqueous solutions. This method is based on a type of reversed-phase chromatography involving ion pair formation of protonated nicotine, cotinine, pyridine, and pyridine derivatives. Detection is accomplished by measuring the UV absorption at 262 nm. Detection limits for nicotine and cotinine are 8 ng/mL and 2 ng/mL, respectively. Analyses of environmental samples and spiked environmental samples by both this ion chromatographic method and a previously reported gas chromatographic method have been used to demonstrate the accuracy and precision of this technique. The results of the analyses of both sets of samples by the two methods are in excellent agreement with a linear correlation coefficient of 0.97.     

催化电位滴定法测定铬鞣剂中铬(Ⅲ)

报道了以氨三乙酸存在下锰(Ⅱ)催化KIO4氧化结晶紫的反应指示终点,结晶紫电极作指示电极用催化电位滴定法测定铬鞣剂中Cr(Ⅲ)的方法。该法终点灵敏、准确度高、重现性好,结果满意,用标准加入法测得的平均回收率为100.03%,RSD为0.24%。