Precipitation of zinc sulfide by the hydrolysis of thioacetamide

Zinc can be precipitated quantitavely as zinc sulphide using thioacetamide in a weakly acid solution. This is accomplished by carrying out the reaction in a sealed tube at 120⁰. The method, however, does not give a good separation from cobalt. Best separations are obtained by using a sulfate-bisulfate buffer containing ammonium thiocyanate with hydrogen sulfide as precipitant.     

Use of diethazine hydrochloride for the extractive spectrophotometric determination of uranium and as a redox indicator

Optimum conditions have been established for the formation and extraction of the complex formed from diethazine, thiocyanate and uranium(VI). An extractive spectrophotometric method for the determination of uranium(VI) is described. Experimental conditions have been also established for the direct titrimetric determination of uranium(IV) with potassium dichromate, using diethazine hydrochloride as redox indicator. Interferences have been considered.     

Preparation of Primary Thioamides From Nitriles Using Sodium Hydrogen Sulfide and Diethylamine Hydrochloride

Primary thioamides are prepared in moderate to excellent yields by treating nitriles with sodium hydrogen sulfide and diethylamine hydrochloride in an appropriate solvent with mild heating.     

Spectrophotometric determination of acid volatile sulfide in river sediments by sequential injection analysis exploiting the methylene blue reaction

This paper demonstrates the application of sequential injection analysis to perform sulfide determination using the methylene blue chemistry, based on two reagents: 3.63 mmol l(-1)N,N dimethyl-p-phenylene diamine hydrochloride in 1.1 mol l(-1) HCl solution and 19 mmol l(-1) FeCl(3), also in 1.1 mol l(-1) HCl. These solutions are aspirated inside the holding coil of the sequential injection system as two reagent zones sandwiching the sample zone. Under optimized conditions, the detection limit was calculated at 40 mug l(-1) S(2-), with a linear dynamic range from 0.05 to 2 mg l(-1) S(2-). This linear range can be extended up to 32 mg l(-1) using in-line dilution for sulfide concentrations greater than 2 mg l(-1). The robust characteristic of the SI system with syringe pump leads to very stable analytical curves (precision of 4%), minimizing the laborious preparation of sulfide standards. The method was applied in the determination of acid volatile sulfide in river sediments.     

A Chemo-enzymatic Route for the Preparation of Chiral （S）-3-Hydroxy-3-phenylpropanoic Acid

（S）-3-Hydroxy-3-phenylpropanoic acid is a potential progenitor of optically pure tomoxetine hydrochlo- ride and fluoxetine hydrochloride which are currently available antidepressant drugs. We report here the chemical synthesis of racemic substrate （R,S）-ethyl 3-hydroxy-3-phenylpropanoate and enzymatic preparation of S-isomer of the substrate by employing Porcine pancreas lipase（PPL） as a biocatalyst. Optimum enzyme-catalyzed reaction con- ditions, such as the effects of the temperature, pH and solvents on conversion degree and enantiomeric excess, were studied. An optimal temperature of 35 ℃ and pH=7.5 are the best for the resolution of （R,S）-ethyl 3-hydroxy-3- pheylpropanoate by PPL when 0.1 mol/L phosphate buffer solution acts as a medium. This work provides a practi- cally chemo-enzvmatic oreoaration of chiral β-hvdroxv acid by PPL.     

Development and validation of a capillary electrophoresis method for the determination of phenothiazines in human urine in the low nanogram per milliliter concentration range using field-amplified sample injection

A capillary zone electrophoresis (CZE) method with ultraviolet-visible detection has been established and validated for the determination of five phenothiazines: thiazinamium methylsulfate, promazine hydrochloride, chlorpromazine hydrochloride, thioridazine hydrochloride, and promethazine hydrochloride in human urine. Optimum separation was obtained on a 64.5 cm x 75 microm bubble cell capillary using a buffer containing 150 mM tris(hydroxymethyl)aminomethane and 25% acetonitrile at pH 8.2, with temperature and voltage of 25 degrees C and 20 kV, respectively. Naphazoline hydrochloride was used as an internal standard. Field-amplified sample injection (FASI) has been applied to improve the sensitivity of the detection. Considering the influence of parameters affecting the on-line preconcentration (nature of preinjection plug, sample solvent composition, injection times, and injection voltage) and due to the significant interactions among them, in this paper we propose for the first time the application of a multivariate approach to carry out the study. The optimized conditions were as follows: preinjection plug of water for 7 s at 50 mbar, electrokinetic injection for 40 s at 6.2 kV, and 32 microm of H3PO4 in the sample solvent. Also, a solid-phase extraction (SPE) procedure is developed to obtain low detection limits and an adequate selectivity for urine samples. The combination of SPE and FASI-CZE-UV allows adequate linearities and recoveries, low detection limits (from 2 to 5 ng/mL), and satisfactory precisions (3.0-7.2% for an intermediate RSD %).     

Heterocyclic synthesis with nitriles: Synthesis of some new thiocyanato-substituted heterocycles from alkylidene malononitrile

α-(Thiocyanatomethyl)benzylidenemalononitrile undergoes bromination with N-bromo succinimide to afford α-(bromothiocyanatomethyl)benzylidenemalononitrile. This bromo derivative undergoes reactions with sodium hydrogen sulfide, thioglycollic acid, hydroxylamine hydrochloride, phenylhydrazine, and hydrazine hydrate to afford thiophene, 4H-thiopyran, 4H-oxazine, pyridazine, and bis(thiazol-2-ylidene)azine derivatives, respectively. Mechanistic explanations as well as structure elucidations are discussed.     

PREPARATION AND PHOTOSENSITIVITY OF WATER SOLUBLE PHENOLIC RESINS CONTAINING ACRYLOYL AND QUATERNARY AMMONIUM CHLORIDE GROUPS

New water soluble and photocrosslinkable prepolymers colltaining acrylate and quaternary ammonium salt groupswere synthesized from epoxy phenolic resin via ring-opening reaction with acrylic acid and with aqueous solution oftriethylamine hydrochloride successively. The second reaction needs no phase transfer catalyst to accelerate, since theproduct formed can act as a phase transfer catalyst. The prepolymer obtained contains both photocrosslinkable acrylategroups and hydrophilic quaternary ammonium salt groups. Optimum conditions for these reactions were studied. Thephotosensitivity of the prepolymer was also investigated. The effects of different photoinitiators, different crosslinkablediluent monomers and amine accelerator on the photosensitivity of the prepolymer were compared. The photoinitiator ofhydrogen abstraction type is still effective without using amine or alcohol as accelerator, because the prepolymer containsα H beside the OH groups formed in the ring-opening reactions     

Analogues of antipsychotic phenothiazines. 10-(β-dialkylamino) ethylaminophenothiazines

A series of 10-(β-dialkylaniino) ethylarninophenothiazines III was obtained by lithium alumi-um hydride reduction of 10-dialkylaminoacetylaminophenothiazines II. Compounds II were synthesized by intramolecular cyclization, via a Smiles rearrangement, of 2-nitro-2′-(β-dialkyl-aminoacetyl) hydrazinodiphenyl sulfides I and XI, which in turn were best prepared by condensation of the appropriate dialkylaminoacetic acid hydrochloride with the corresponding 2-nitro-2′-hydrazinodiphenyl sulfide in the presence of dicyclohexyl carbodiimide. Other attempted methods for the synthesis of compounds 1 are also described.     

Stabilization of lead sulfide nanoparticles by polyamines in aqueous solutions. A structural study of the dispersions

Lead sulfide (PbS) nanoparticles have been synthesized in aqueous solutions by a reaction between inorganic lead salts and sodium sulfide and stabilized using the cationic polyelectrolytes branched poly(ethylenimine) (PEI), poly(allylamine hydrochloride) (PAH), and poly(diallyldimethylammonium chloride) (PDDA). The structures of the polyamine-stabilized nanoparticle dispersions were examined in detail using UV-vis spectroscopy, small-angle X-ray scattering (SAXS), static and dynamic electrophoretic mobility measurements, and transmission electron microscopy (TEM). Considerable differences were found between the stabilizing efficiencies of these polyelectrolytes, which cannot be attributed to their charge densities or their persistence lengths. Small monodisperse nanoparticles of PbS with a tight stabilizing shell were consistently found only when PEI was used as a stabilizer even at high pH values, although its charge density is then very low. The excellence of PEI as a stabilizer is mainly due to the extensive branching of the chains and the presence of uncharged secondary and tertiary amine groups, which apparently serve as good anchoring points at the nanoparticle surfaces. None of the polyelectrolytes examined here provide long-term protection of the nanoparticles toward oxidation by air, showing that a need for more complex multipurpose stabilizers exists for aqueous PbS dispersions.     

One-Pot Three-Component Synthesis of 3-Methyl-4-Arylmethylene- Isoxazol-5(4H)- Ones Catalyzed by Sodium Sulfide

Abstract

3-Methyl-4-arylmethylene-isoxazol-5(4H)-ones were synthesized by the convenient three-component reaction of ethyl acetoacetate, hydroxylamine hydrochloride, and aromatic aldehydes catalyzed by sodium sulfide in the presence of ethanol at room temperature. The advantages of this procedure were mild reaction conditions, high yields, short reaction time, and operational simplicity.     

Catalytic Photometric Determination of Selenium by Flow Injection Analysis

A method is developed for the determination of trace amounts of selenium by flow injection analysis based on the catalytic effect of this element. Catalytic enhancement by selenium for the reduction of picrate ion by sodium sulfide was used and photometrically measured at the wavelength, 470nm. Optimum conditions were determined for temperature, pH, the concentrations of picrate and sodium sulfide, and also the conditions of the flow system; injection of sample volume, flow rate and mixing coil length. With these conditions a good linear relationship was obtained for selenium in the range from 0.1 ppm to 1.0ppm and the detection limit was about 5ppb (two times of the noise). Interference by the diverse ions can be avoided with the use of a precolumn cation exchanger (Dowex 50) and by masking with EDTA in the conditional stream.     

Copper Sulfide Wire as a Selective Fiber in Solid-Phase Microextraction

Summary A copper wire coated with copper sulfide (CuS) was investigated as fiber for solid-phase microextraction (SPME). The fibers seem very effective for extraction of aliphatic alcohols and amines from aqueous samples. Optimum conditions for the preparation and conditioning of the fibers are presented. Scanning electron microscopy shows the formation of a porous CuS layer with a thickness of ca. 9 m. The calibration graph for benzyl alcohol was linear in the range 10–100 ppb. The detection limit for benzyl alcohol and GC-FID was 2 ppb (S/N=3).     

Photometric determination of traces of antimony with rhodamine b after sulfide precipitation

A method is described for the colorimetric determination of as little as a few tenths of a part per million of antimony in samples composed primarily of elements of atomic numbers 1–28 (e.g., geo materials).Antimony is isolated by sulfide precipitation in mineral acid medium after reduction of ferric iron with hydroxylamine hydrochloride, with final determination by rhodamine B-benzene extraction. The procedure provides for the presence of gallium, thallium, tungsten and gold.     

Kinetics of precipitation and growth of thin indium(III) sulfide films

Thin films of indium(III) sulfide have been prepared by chemical precipitation from aqueous solutions containing indium(III) nitrate, thioacetamide, tartaric acid, and hydroxylamine hydrochloride at 333–368 K. Kinetics of In₂S₃ precipitation and the films growth under conditions of spontaneous formation of the solid phase in the solution has been studied. Formal rate law of indium(III) sulfide formation accounting for the partial orders of In₂S₃ precipitation with respect to the system components and the process activation energy has been derived. The effects of the reaction mixture composition, temperature, and the synthesis duration of In2S3 films growth have been studied.     

Easy sample treatment for the determination of enrofloxacin and ciprofloxacin residues in raw bovine milk by capillary electrophoresis

An easy, selective, and sensitive method has been developed for the determination of enrofloxacin (ENR) and its main active metabolite, ciprofloxacin (CIP), in raw bovine milk using CE with UV detection at 268 nm. Milk samples were prepared by a clean‐up/extraction procedure based on protein precipitation with hydrochloride acid followed by being defatted by centrifugation and SPE using a hydrophilic‐lipophilic balance cartridge. Optimum separation was obtained using a 50 mM phosphoric acid at pH 8.4 and the total electrophoretic run time was 6 min. Sample preparation by this method yielded clean extracts with quantitative and consistent mean recoveries from 89 to 97% for CIP and from 93 to 98% for ENR. LODs obtained were lower to the maximum residue limits for these fluoroquinolones. The precision of the ensuing method is acceptable; thus, the RSD for peak area and migration time was less than 8.5 and 0.5% for CIP and 9.9 and 0.9% for ENR, respectively. The results showed that the proposed method was efficient showing good recoveries, sensitivity, and precision for the studied compounds and could be satisfactorily applied in routine analysis for the monitoring of ENR and CIP residues in milk, due to its ruggedness and feasibility demonstrated.     

Mild method for the conversion of amides to thioamides

Aqueous ammonium sulfide was found to be an ideal substitute for hydrogen sulfide for the thiolysis of activated amides. High yields of the corresponding thioamides were obtained for a broad range of substrates, using two different procedures that are both operationally simple and inexpensive, as well as amenable to large-scale preparation. Preliminary results indicate that aqueous ammonium sulfide may also replace hydrogen sulfide in the synthesis of thionoesters from amides.     

New Germaheterocycles,Germadithioacetals and a Germylated Oxide and Sulfide Derived from Cysteamine,Methylcysteamine and N-Substituted Cysteamine: Synthesis and Radioprotective Activity

Further to our work concerning organometallic compounds active in chemical radioprotection, we report the synthesis and pharmacological study (radioprotective activity, toxicity) of new germathiazolidines and germadithioacetals derived from cysteamine, methylcysteamine and N -substituted cysteamine. A germylated oxide and sulfide with methylcysteamine hydrochloride as ligand were also investigated. A notable decrease in the toxicity and a fairly large increase in the radioprotective activity of these new organogermylated compounds were observed compared with cysteamine, methylcysteamine and N -substituted cysteamine.     

硫化锌胶体标准溶液稳定性研究

采用去离子除氧水,由淀粉、乙酸锌、氯化钠、硫化钠等配制了硫化锌胶体标准溶液。实验结果表明,硫化锌胶体标准溶液的吸光度与硫化钠标准溶液基本一致,可以替代硫化钠标准溶液。采用t检验对硫化物胶体标准溶液稳定性进行了检验,表明该法配制的硫化锌胶体标准溶液在室温下可稳定保存2个月,解决了硫化物标准溶液只能现配现标现用的问题。     

Hydrogen sulfide as a source of hydrogen production

Potentialities and perspectives of using the known processes of hydrogen sulfide decomposition (thermal, plasmochemical, electrochemical, and photochemical) to produce hydrogen are examined. The results of theoretical and experimental studies of hydrogen sulfide dissociation on the surface of single crystals are presented. The data on the low-temperature decomposition of H₂S on the sulfide and metal catalysts are discussed. The electronic structure of diatomic sulfur and thermodynamics of its formation in the processes of H₂S decomposition are considered. The decomposition of hydrogen sulfide on the heterogeneous catalysts placed under the solvent layer is shown to be promising. The mechanism of assimilation of hydrogen sulfide by colorless sulfur bacteria is proposed.