N-p-tolyl-2-furohydroxamic Acid as the Extracting and Spectrophotometric Reagent for Vanadium(V)

Abstract

A simple and rapid spectrophotometric determination of vanadium(V) is described. The vanadium-N-p-tolyl-2-furohydroxamic acid complex is extracted into chloroform form 6–8 molar hydrochloric acid solution. Maximum absorbance occurs at 540 nm and Beer's Law is obeyed over the range of 0–15 μg of vanadium in the organic phase. The molar absorptivity is 3.0 × 10³ mole^?1 cm^?1 at 540 nm.

Vanadium could be determined in high purity niobium and tantalum metals, cast iron, steel, non ferrous alloys and silicates. Vanadium could be determined in the presence of several commonly occurring cations.     

Colorimetric Microdetermination of some Corticosteroid Drugs Using Indophenol as Chromophoric Reagent

Abstract

A simple, rapid and sensitive method for the determination of betamethasone (I), dexamethasone (II) and hydrocortisone (III), either in the pure form or in pharmaceutical formulations is described. The method is based on the development of a brown product with indophenoi in basic aqueous-ethanolic (50% v/v) medium. The optimum reaction conditions for the charge transfer complex formed were assessed. The absorbance measurements were made at 820, 816 and 822 nm for I, II and III respectively. The calibration graph was linear in the range 1-26, 1-32 and 1-35 μg/ml of I, II and III with slopes of 0.028, 0.021 and 0.024, respectively. For more accurate analysis, Ringbom optimum concentration ranges were 2.5-23.0, 3.0-28.5 and 3.0-33.0 μg/ml for I, II and III, respectively. The precision of the procedure was checked by calculating the relative standard deviation of ten replicate determinations on a sample containing 20 μg/ml for each drug and was found to be 1.67, 1.39 and 1.85% for I, II and III, respectively. Many common excepience and common drugs present in their dosage forms do not interfere, and the tolerable levels were evaluated. Results of analysis of pure drugs and their dosage forms by the proposed method are in good agreement with those of the British Pharmacopoeia 1993 procedure.     

卤氧化铋化合物光催化剂

卤氧化铋,BiOX (X=Cl, Br, I)作为一种新型光催化剂,由于具有特殊的层状结构和合适的禁带宽度从而显示出优异的光催化性能。本文主要对微纳米卤氧化铋光催化剂的制备方法、形貌尺寸及光催化性能进行了综述。卤氧化铋的光催化活性普遍优于商品TiO₂ (P25)的光催化活性,并且随着卤素原子序数的增加光催化活性逐渐增强。此外,卤氧化铋光催化剂还具有很高的稳定性。借助于掺杂改性,卤氧化铋的光催化性能得到进一步改善;通过晶体结构和能带结构的设计合成可以得到高活性的卤氧化铋化合物光催化剂。最后,对卤氧化铋光催化剂今后的研究方向进行了展望。     

硅酸铋(BSO)纳米粉体的制备与表征

Bismuth silicate nanopowders were prepared by the sol-gel method. Tetraethyl orthosilicate (TEOS) and Bi₂O₃ were used as the starting materials. The precursors were heat-treated at 750℃ for 2 h. The size distribution of Bi₄Si₃O₁₂ nanopowders is 40～100 nm. The TG-DTA curves, the XRD patterns and the TEM microphotograph of Bi₄Si₃O₁₂ are discussed. Compared with crystal materials, the excitation spectra and the emission spectra of Bi₄Si₃O₁₂ nanopowders indicate blue shift.     

铋单质及其复合材料在光催化中的应用

单质铋作为近年来报道的新型光催化材料受到了研究者的广泛关注,本文主要介绍了铋单质的光敏化、半导体光催化及等离子体共振光催化机理。阐述了以沉淀法、溶剂热法、电化学法为代表的铋单质光催化材料的主要制备方法,并探讨了制备方法中表面活性剂、反应温度以及pH对合成铋单质的影响。归纳了铋单质尺寸和形貌对其吸光性能的影响。在此基础上进一步综述了以铋-二氧化钛、铋-铋系氧化物、铋-氧化锌、铋-氮化碳（C₃N₄）为主要代表的铋-半导体复合光催化材料,并归纳了其光催化增强机理,最后阐述了铋单质及其复合光催化材料的发展趋势。     

Dimedone as an Analytical Reagent for the Colorimetric Determination of Paracetamol and Oxyphenbutazone

Abstract

Dimedone is used here for the colorimetric determination of paracetamol and oxyphenbutazone both in pure form and in their tablets. Paracetamol and oxyphenbutazone are first nitrated and the nitroderivatives produced are extracted into ethyl actetate. Dimedone is added in the presence of triethylamine and a highly coloured complex is formed. The concentration ranges adhering to Beer's law are 0.01 - 0.1 mg/ml for oxyphenbutazone and 0.03 - 0.1 mg/ml for paracetamol.     

Solid Phase Extraction and Spectrophotometric Determination of Mercury in Tobacco and Tobacco Additives with p-Sulfobenzylidenerhodanine as Chromogenic Reagent

A highly sensitive, selective and rapid method for the determination of mercury based on the reaction of mercury(II) with p-sulfobenzylidenerhodanine (SBDR) and the solid phase extraction of the colored chelate with a C₁₈ cartridge has been developed. In the presence of pH 3.8 acetate buffer solution and Tween-80 medium, SBDR reacts with mercury to form a red chelate of a molar ratio of 1:2 (mercury to SBDR). This chelate was enriched by solid phase extraction with a C₁₈ cartridge and eluted from the cartridge with ethanol (containing 5% acetic acid). The enrichment factor of 50 was achieved. In the ethanol medium, the molar absorptivity of the chelate is 1.28×10⁵L·mol^–1·cm^–1 at 545nm. Beers law is obeyed in the range of 0.011.2µgmL^–1 in the measured solution. The relative standard deviation for eleven replicate samples of 0.01µgmL^–1 level is 1.52%. This method can be applied to the determination of mercury in tobacco and tobacco additives with good results.     

A Novel Colorimetric Reagent for Potassium Based on Crown Ether Complex Formation

Abstract

The extraction study of alkali metal ions was made with a new type of crown ether, 4′-picrylaminobenzo-15-crown-5 (HL). Upon dissociation in alkaline medium orange-colored HL gives blood-red anion, L^?, and extracts selectively K⁺ (and to a lesser extent Rb⁺) ion into chloroform as a colored complex of composition ML·HL. A colorimetric determination of 10 - 400 ppm K⁺ in the presence of < 2000 ppm Na⁺ was possible using this new crown ether reagent.     

4-Aminoantipyrine as an Analytical Reagent for the Colorimetric Determination of Tetracycline and Oxytetracycline

Abstract

A spectrophotometric method is proposed for the determination of tetracycline and oxytetracycline and their dosage forms. The suggested method depends on the reaction with 4-aminoantipyrine in the presence of an alkaline oxidising agent. A red antipyrine dye is produced. The reaction ratio has been determined. Variables such as pH, temperature, reagent concentration, stability of the colour produced have been evaluated to permit selection of the most advantageous technique. Beer's law was obeyed over the concentration range 0.04 - 0.12 mg/ml and 0.04 - 0.16 mg/ml for tetracycline and oxytetracycline respectively.     

Colorimetric Determination of Ampicillin and 6-Aminopenicillanic Acid Using Acenaphthenequinone as a Chromophoric Reagent

Abstract

A colorimetric method for the determination of ampicillin (Amp.) and 6-aminopenicillanic acid (6-APA) are described, based on the reaction of these drugs with acenaphthenequinone in basic media to give a highly intense red coloured product. The latter exhibits an absorption maximum at 610 nm with apparent molar absorptivities of 2.83 and 1.45 × 10⁴ l. mol^?1 cm^?1 and Sandell sensitivities of 0.013 and 0.015 μg cm^?2 for Amp. and 6-APA, respectively. The optimum concentration ranges are 0.4-10 and 0.4-14 μg ml^?1 for Amp. and 6-APA, respectively. For more accurate results, Ringbom optimum concentration ranges are 1–8.5 and 1–12 μg ml^?1 for Amp. and 6-APA, respectively. Statistical analysis indicated that there was no significant difference between the results obtained by the described method and those of the official methods. The mean recoveries percentage were found to be 99.5 × 1.1% for pharmaceutical formulations and 99.1 × 1.6% for serum and urine samples. The method is selective for the determination of Amp. or 6-APA in the presence of their degradation products, additives and excipiences that are normally encountered in dosage forms. The proposed method was applied successfully to the determination of Amp. in pharmaceutical formulations. Also, applicability of the proposed method to human serum and urine is presented and the validity assessed by applying the standard addition technique.     

A New Colorimetric Reagent for Carbon Monoxide

Abstract

A new colorimetric reagent for carbon monoxide is described. The reaction sequence apparently involves reduction by carbon monoxide of [PdCl₄]^2-, which then reduces [Fe^III EDTA]^? to [Fe^IIEDTA]^2-. The latter undergoes ligand exchange with 2,2′-dipyridyl or 1,10-phenanthroline to form the more stable colored [FeL₃]²⁺, which is measured spectrophotometrically. Sodium molybdate enhances the overall reaction. The color intensity produced is non-linear but reproducible. The method is unique in that a soluble colored compound is produced rather than a metal sol.     

铋纳米管的快速合成与表征

以铁粉作还原剂在水溶液中通过置换反应在室温下成功地合成了铋纳米管,并采用透射电子显微镜、电子衍射、X射线粉末衍射仪和热重分析仪对样品进行了鉴定和表征．结果表明所合成的样品呈肩并肩式的管状结构,管径比较均一,并具有高的结晶性和相纯度．热重分析显示所制备的样品含有约3．2％的有机物,并具有良好的热稳定性能．     

Diaminobenzene as a Novel Reagent for Nitrite Assay in Environmental Samples: Evidence for Its Mechanistic Aspects

Abstract

o-Phenylenediamine has been used as a reagent to quantify nitrites/nitrates in a variety of sample matrices. The method is based on the cyclization reaction between o-phenylenediamine and nitrite in acid medium. The amine undergoes diazotization with nitrite in the presence of acid to form the diazonium ion, which subsequently cyclizes to yield yellowish orange benzotriazole at room temperature with an absorption maximum at 450 nm. The formed dye has been separated, purified, and characterized by IR, NMR, and spectroscopy techniques. The parameters of the reaction between amine and nitrite have been optimized. The effect of interfering ions on the determination of nitrites/nitrates has been described. The developed method has been applied for the determination of residual NO₂ gas present in the ambient air after fixing it as a nitrite ion using sodium arsenite as a trapping medium. The dye formed has been extracted into organic solvent to improve the detection limit during the measurement of low levels of ambient NO₂ in air. The method obeyed Beer's law in the concentration range 0–250 µg in aqueous medium and 0–50 µg in organic medium with molar absorptivity of 4.09 × 10⁴ L mol^?1 cm^?1 and 4.3 × 10⁴ L mol^?1 cm^?1 respectively. Nitrate is determined by reducing it to nitrite after passing through the copperized cadmium reductor column. The developed method has been applied to determine nitrite/nitrate levels in water, soil, and biological samples.     

A Novel Method for the Determination of Streptomycin Using Sodium Nitroprusside as a Chromogenic Reagent by Spectrophotometry

Abstract

A rapid and simple spectrophotometric method for the determination of streptomycin has been developed and validated. The method was based on the reaction of streptomycin with sodium nitroprusside in the alkaline medium forming a red product measured at the maximum absorption of 495 nm. The stoichiometric ratio of the product is 1:1. Beer's law is obeyed in a range of 1.87 µg mL^?1 ～ 279.8 µg mL^?1 of streptomycin and ?₄₉₅ is 6.0 × 10³ L·mol^?1 cm^?1.Under the optimum condition, the equation of linear regression is A = 0.00742 + 0.05683 C (× 10⁵ mol·L^?1), with a linear correlation coefficient of 0.9990. The detection limit (3σ/k) is 0.96 µg mL^?1, the relative standard deviation (RSD) is 2.40%, and the average recovery rate is 98.3%–102.7%. Every parameter has been optimized, and the reaction mechanism has been studied. The proposed method has been successfully applied to the determination of streptomycin for injections and tablets of pharmaceutical preparation. Analytical results obtained by this new method were very gratifying.     

聚乙烯醇缩对甲酰基偶氮磺的合成和液—固萃取分离镍,铜,锌的研究

报道了２－（４－磺酸苯偶氮）－７－（４－甲酰基苯偶氮）－１,８－二羟基－３,６－萘二磺酸以及在偶氮磺与聚乙烯醇（ＰＶＡ）的缩合产物的合成及其性质。并从试剂的结构和反应机理方面对ＳＡｐＦ和ＰＶ·ＳＡｐＦ的分析性能进行了对比研究。实验结果表明,采用高分子显色剂做萃取剂,易获得萃取率和好的分离效果,且萃取不受被萃物结构和电性的影响。     

Promotional Effect of Bismuth as Dopant in Bi-Doped Vanadyl Pyrophosphate Catalysts for Selective Oxidation of n-Butane to Maleic Anhydride

Bismuth-promoted (1% and 3%) vanadyl pyrophosphate catalysts were prepared by refluxing Bi(NO3)3·5H2O and VOPO4·2H2O in isobutanol. The incorporation of Bi into the catalysts lattice increased the surface area and lowered the overall V oxidation state. Profiles of temperature programmed reduction (TPR) in H2 show a significant shift of the maxima of major reduction peaks to lower temperatures for the Bi-promoted catalysts. A new peak was also observed at the low temperature region for the catalyst with 3% of Bi dopant. The addition of Bi also increased the total amount of oxygen removed from the catalysts. The reduction pattern and reactivity information provide fundamental insight into the catalytic properties of the catalysts. Bi-promoted catalysts were found to be highly active (71% and 81% conversion for 1% and 3% Bi promoted catalysts, respectively, at 703 K), as compared to the unpromoted material (47% conversion). The higher activity of the Bi-promoted catalysts is due to that these catalysts possess highly active and labile lattice oxygen. The better catalytic performance can also be attributed to the larger surface area.     

Molecular Bismuth Cations: Assessment of Soft Lewis Acidity

Three-coordinate cationic bismuth compounds [Bi(diaryl)(EPMe₃)][SbF₆] have been isolated and fully characterized (diaryl=[(C₆H₄)₂C₂H₂]²⁻, E=S, Se). They represent rare examples of molecular complexes with Bi⋅⋅⋅EPR₃ interactions (R=monoanionic substituent). The ³¹P NMR chemical shift of EPMe₃ has been found to be sensitive to the formation of LA⋅⋅⋅EPMe₃ Lewis acid/base interactions (LA=Lewis acid). This corresponds to a modification of the Gutmann–Beckett method and reveals information about the hardness/softness of the Lewis acid under investigation. A series of organobismuth compounds, bismuth halides, and cationic bismuth species have been investigated with this approach and compared to traditional group 13 and cationic group 14 Lewis acids. Especially cationic bismuth species have been shown to be potent soft Lewis acids that may prefer Lewis pair formation with a soft (S/Se-based) rather than a hard (O/N-based) donor. Analytical techniques applied in this work include (heteronuclear) NMR spectroscopy, single-crystal X-ray diffraction analysis, and DFT calculations.     

Polarographic Determination of Bismuth Sensitization in the Presence of Nioxime

Abstract

Nioxime sensitizes the differential pulse polarographic determination of B1(III) in alkaline medium and in the presence of tart rate and citrate; detection limits of 8 and 12 ppb are obtained. Characterization of the electroactive process included an examination of the degree of reversibility and the effect on the peak current of pH, buffer composition, nioxime and bismuth concentrations and the presence of other metal ions.