Spectrophtometric determination of tungsten(VI) with rutin and cetyltrimethylammonium bromide

Tungsten-(VI) reacts with rutin in the presence of cetyltrimethylammonium bromide to form a soluble yellow complex having maximum absorbance at 416 nm. The molar ratio of tungsten to rutin in the complex is 1:2. The molar absorptivity is 5.01 x 10(4) 1.mole(-1).cm(-1). Beer's law is obeyed over the range 1 x 10(-7)(-1) x 10(-5)M tungsten (VI). Optimum solution conditions for the determination of tungsten in various sample matrices have been found and the interference of diverse ions has been examined.     

Chemiluminescence determination of nitrate with photochemical activation in a flow injection system

A chemiluminescence flow injection system is described for the determination of nitrate, involving use of a laboratory-built flow-through photochemical reactor. Optimum analytical conditions were established. The linear range for nitrate is 7 x 10(-8)-1 x 10(-4)M. The sampling frequency is 60 samples per hour. The relative standard deviation for 1 x 10(-7), 1 x 10(-6) and 1 x 10(-5)M nitrate is 0.97, 0.84 and 0.76%, respectively. The method has been applied to the determination of nitrate in natural water samples, and recoveries of 96-103% have been attained.     

Fluorimetric trace determination of cerium(III) with sodium triphosphate

Sodium triphosphate acts as a specific reagent for enhancing the fluorescence intensity of cerium(III). The purpose of this study was to investigate the spectrofluorimetric determination of trace amounts of Ce(III) in sodium triphosphate solution. The excitation and emission wavelengths are 303.5 nm and 353 nm respectively. Optimum sodium triphosphate concentration is found to be 0.074 g l(-1) at room temperature. The fluorescence varies linearly with the concentration of cerium(III) in the range 0.001-45 mug ml(-1). The detection limit is 9.4 x 10(-4)mug ml(-1). The relative standard deviations for 30 mug ml(-1) and 0.05 mug ml(-1) Ce(III) in 0.074 g l(-1) sodium triphosphate solution are 1.1% and 0.72% respectively. Quenching effects of other lanthanides and some inorganic anions are described. This method is a direct and rapid analytical method for the determination of Ce(III) in rare earth mixtures and cerium concentrates.     

Triphenyltetrazolium chloride for determination of iodate and periodate

Optimum conditions for complexation in the systems triphenyl-tetrazolium chloride-iodate-iodide-dichlorethane and triphenyltetrazolium chloride-periodate-iodide-dichlorethane were found. The molar absorptivity of the complex was 7.48 x 10(4) 1. mole(-1). cm(-1) for the iodate, and 9.09 x 10(4)1. mole(-1) cm(-1) for the periodate. Beer's law is adhered to in the range of 0.04-0.7 mug/ml for iodate and 0.02-0.35 mug/ml for periodate. The influence of foreign ions was studied. Cr(VI), Hg(II) and S(2)O(2-)(3) interfere. The proposed method has been applied to analysis of iodate and periodate in fresh water.     

Determination of cefadroxil by sequential injection with spectrophotometric detector.

A sequential injection analysis (SIA) spectrophotometric procedure for cefadroxil determination has been developed. The SIA instrumentation was modified to achieve the desired function and operations by using the software developed to interface the PC with the conventional SIA system. The method is based on the measurement of a red, water-soluble product formed by the reaction between cefadroxil and 4-aminoantipyrine in the presence of alkaline potassium hexacyanoferrate(III) at 510 nm. Optimum conditions for determining the drug were investigated. Beer's law was obeyed over the concentration ranges of 1 - 10 mg L(-1) and 10 - 50 mg L(-1) with a detection limit (3 sigma) of 0.17 mg L(-1) and a limit of quantification (10 sigma) of 0.56 mg L(-1). The relative standard deviations of 1.98% and 1.93% for 5 mg L(-1) and 30 mg L(-1) of the drug, respectively (n = 11) are obtained. The proposed method has been applied satisfactorily to the determination of cefadroxil in commercial pharmaceutical formulations with a sampling rate of 100 h(-1). Results obtained were in good agreement with those obtained by the official HPLC method at the 95% confidence level.     

Spectrophotometric determination of lanthanum, thorium and iron(III) with chromotropic acid azo dyes of the pyridine series

Highly sensitive methods for the determination of lan thanum, thorium and iron(III) have been developed with the sodium salts of 2-(pyridyl-2-azo)chromotropic acid, 2-(pyridyl-3-azo)chromotropic acid and 2-(2-carboxypyridyl-3-azo)chromotropic acid. Optimum concentration ranges are of the order 1-20 ppm. The effect of diverse ions (cations and anions) including those of rare-earths are reported. The nature of the complexes has been investigated and values for the instability constants are given.     

Amperometry with two polarisable electrodes-XI Determination of bismuth by EDTA titration

Optimum conditions have been found for a highly selective determination of bismuth via EDTA titration with biamperometric indication of the end-point. The influence of the applied potential, pH and stirring on the accuracy and selectivity of the determination has been studied. In a medium of 0.4M nitric acid only high concentrations of iron(III) and copper(II) interfere with the determination of bismuth. Zirconium, thallium(III) and indium interfere even in small concentrations. The average error of the determination of 5-100 mg of bismuth (when titrated with 0.05M EDTA solution) is +/-0-1 % rel. and for the determination of 0.5-10 mg it is +/-0.3% rel. (0.005M EDTA). The method has been verified by the analysis of a Wood's metal of known composition.     

Determination of trace amounts of manganese in nickel by fourth-derivative spectrophotometry

Fourth-derivative absorption spectra were used to determine trace amounts of manganese in nickel salts. Optimum conditions for the oxidation of microgram amounts of Mn(II) to MnO(-)(4) in the presence of large amounts of nickel were established. Fourth-derivative spectra provided good sensitivity and selectivity for this determination. Attention has been paid to the effect of instrumental parameters on the results obtained. Limitations of the peak-to-trough and zero-crossing measurement techniques have been examined. Manganese (1 x 10(-3)-2 x 10(-5)%) in nickel salts (nitrate, sulphate and chloride) and in nickel powder was determined with good precision and accuracy.     

Determination of yttrium in rare earths by photon activation analysis

The determination of yttrium in the presence of large amounts of the rare earths by the thermal neutron reaction (89)Y(n, gamma)(90)Y is complicated because of frequent problems of sample self-shielding from major constituents of the sample, and the difficulty of separating (90)Y, a pure beta-emitter, from other elements which are very similar chemically. A non-destructive photon activation analysis method has been developed for this determination. Bremsstrahlung from a 35-muA beam of 35-MeV electrons induces the photonuclear reaction (89)Y(gamma, n)(88)Y. Optimum sensitivity is obtained by coincidence counting of the 0.90 and 1.84 MeV gamma-rays associated with the decay of (88)Y. The detection limit is less than 1 mug of yttrium.     

Preconcentration of copper, nickel and zinc with Amberlite XAD-16 resin

Summary An adsorption-elution and atomic absorption spectrophotometric method using Amberlite XAD-16 is proposed for the preconcentration and determination of Cu, Ni and Zn. Optimum conditions for the preconcentration were investigated. Recoveries of the elements were found to be 82.4±0.3%, 95±3% and 71±1% for Cu, Zn and Ni, respectively, at 95% confidence level. The recoveries were increased to about 99% for Cu and Ni by complexing with 1-(2-pyridylazo)-2-naphthol (PAN). The effect of Na and K on the preconcentration of trace metals has also been investigated. The method was applied to a tap water.     

Spectrophotometric determination of molybdenum with 7,8-dihydroxy-4-methylcoumarin and cetyltrimethylammonium bromide

The 1:2 complexes formed between molybdenum and 7,8-dihydroxy-4-methylcoumarin in the presence and absence of cetyltrimethylammonium bromide (CTAB) have been studied. The binary complex formed at pH 5.6-6.0 in the absence of CTAB exhibits an absortion maximum at 360 nm with a molar absorptivity of 5.1 x 10(4) 1.mole(-1).cm(-1). The complex formed at pH 4.8-6.0 in the presence of CTAB has a molar absorptivity of 1.32 x 10(5) 1.mole(-1).cm (-1) at 400 nm, the wavelength of maximum absorption. Optimum conditions for complex formation were investigated and a rapid, sensitive and relatively selective method for the determination of up to approximately 70% of Mo in diverse alloys and steels is described. Small amounts of zirconium and tungsten interfere.     

Determination of phenol by flow-injection with chemiluminescence detection based on the hemin-catalysed luminol-hydrogen peroxide reaction

This study established a novel flow injection (FI) methodology for the determination of phenol in aqueous samples based on luminol chemiluminescence (CL) detection. The method was based on the inhibition that phenol caused on the hemin-catalysed chemiluminescence reaction between luminol and hydrogen peroxide in alkaline solution. Optimum conditions and possible mechanisms have been investigated. The linear range was 2.0×10(-9) to 4.0×10(-7)gmL(-1) for phenol. The proposed method is sensitive with a detection limit of 4.0×10(-10)gmL(-1). The relative standard deviation for 11 measurements was 2.3% for 1.0×10(-7)gmL(-1) phenol. The method was applied for the determination of phenol in waste water samples. The results obtained compared well with those by an official method.     

气相色谱法测定胶粘剂中的游离甲醛

采用超声波萃取胶粘剂中游离甲醛,经2,4-二硝基苯肼衍生后用气相色谱一电子捕获检测器法测定．对提取方法、衍生化条件及色谱条件进行了研究,确定了甲醛检测的最佳条件．研究数据显示,该方法对甲醛的检出限为0．175μLg／g,在0．1～60．0μg／mL浓度范围内,线性相关系数R^2=0．9999;在1、2和8μg／mL3个添加水平下的添加回收率在98．97％-102．24％之间,5个实验室对同一样品中甲醛含量测定值的相对标准偏差为4．0％．结果表明本方法简便、快速、检测限低、回收率高、重现性好．     

Spectrophotometric determination of platinum with o-phenylenediamine

Platinum(IV or II) reacts with o-phenylenediamine, at pH 6.5, to form light blue solutions having maximum absorption at 703 nm. The reaction, slow at room temperature, is complete in 3-4 min at temperatures near 100 degrees . Use of dimethylformamide in the solution prevents precipitation of the reaction product. The colour is stable for at least 24 hr. Effects of heating temperature and time, pH, reagent concentration, and other variables have been studied. The system conforms to Beer's law over the concentration range investigated. Optimum concentration range for measurement in 10-mm cells is 0.4-1.4 ppm of platinum; the molar absorptivity is 9.83 x 10(3) l. mole(-1). mm(-1). Interference from foreign ions has been evaluated, and methods for removal or masking of interferences have been tested. In the colour-forming reaction, platinum(IV) is reduced by the organic reagent to platinum(II), which is then complexed with the reagent. The metal : ligand ratio of 1 : 2 was indicated by solution spectrophotometric measurements, and was confirmed on the solid reaction product by elemental analysis and by mass spectrometric examination.     

丙烯酰胺与4-乙烯基吡啶共聚物的季胺化及其若干性能

将丙烯酰胺 (AM)与 4 乙烯基吡啶 (4VP)的共聚物 (P(AM co 4VP) )用硫酸二甲酯季铵化 ,制备了系列吡啶季铵盐型阳离子丙烯酰胺共聚物 ,用FTIR、1 H NMR和紫外分光光度法表征了其分子结构与组成 ,并重点研究了其絮凝与缓蚀性 ,考察了阳离子度与分子量对其各种功能的影响 .研究结果表明 ,吡啶季铵盐型阳离子丙烯酰胺共聚物具有优良的絮凝 缓蚀等功能 ,且阳离子度越高 ,性能越好 ,而分子量对其性能亦有显著的影响 .     

Derivative spectrophotometric determination of praseodymium in rare earth mixtures with lomefloxacin

Praseodymium forms a Pr(LMFX)(3) complex with lomefloxacin. In this paper, the absorption spectra of the complex has been investigated by applying conventional and derivative spectrophotometric methods. It was found that lomefloxacin could form a stable complex with praseodymium in the pH 6.5-8.5 media. The absorption intensity of the complex is 4.5-fold more than PrCl(3). Using the second derivative spectra, the sensitivity is 7.4 times higher for Pr than in the normal method (zero derivative spectra). The second derivative spectrophotometry for determination of praseodymium in the presence of other rare earths has been developed. The calibration curves were linear in the range of 3.5-65 mug ml(-1) for Pr. The detection limit is 0.85 mug ml(-1). The method is satisfactory for the determination of praseodymium in mixed rare earths.     

Determination of epinephrine, norepinephrine, dopamine and L-dopa in pharmaceuticals by a photokinetic method.

A study of the photochemical reaction of the Rose Bengal (RB)-ethylenediaminetetraacetic acid system in the presence of epinephrine, norepinephrine, dopamine and L-dopa is presented. The rate of photoreduction of RB is dramatically retarded by small amounts of these catecholamines, which have an inhibitory effect on the excited state of RB, which is the activator of the process. Optimum conditions for the determination of catecholamines in the range of concentration between 5 x 10(-6) and 1 x 10(-4) mol dm-3 are described. The proposed method has been applied with excellent results to the determination of catecholamines in pharmaceuticals.     

Detection of trace levels of trichothecenes in human blood using capillary gas chromatography-electron-capture negative ion chemical ionisation mass spectrometry

A sensitive and selective method has been developed for the simultaneous detection in blood of eleven trichothecenes of widely varying polarity. The procedure involved precipitation of blood proteins with acetone followed by a clean-up using reversed-phase Sep-Pak C18 cartridges. The extracted trichothecenes were derivatised as their pentafluoropropionyl esters, separated using capillary gas chromatography and detected using electron-capture negative ion chemical ionisation with methane reagent gas and selected-ion monitoring. Optimum sensitivity and selectivity were obtained using low source temperatures (60 degrees C indicated) and high source pressures (1 Torr indicated). Detection limits on 1-ml blood samples were in the range 0.1-5 ppb. The method was readily adaptable to the detection of other trichothecenes. A protocol was used which minimised the risk of cross-contamination. The method was validated in collaborative studies by the successful analysis of 42 blood samples spiked and submitted blind by two independent laboratories for analysis.     

Oxidative dehydrogenation of alkylheteroaromatic compounds. 2*. Dehydrogenation of alkylthiophenes

Summary The dehydrogenation of a series of alkylthiophenes has been studied on vanadium-magnesium systems in the presence of atmospheric oxygen, and on zinc-chromium oxide catalysts in the absence of oxygen. Optimum conditions have been determined for bringing this about enabling vinylthiophenes to be obtained in high yield and with high selectivity. The advantages of the oxidative dehydrogenation method have been shown in the synthesis of vinyl derivatives of thiophene.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1034-1037, August, 1994.     

Spectrophotometric method for the determination of manganese with phenylfluorone in the presence of Triton X-100 and cetylpyridinium chloride in pharmacological preparations and vegetable fertilizers

A simple and very sensitive method for the spectrophotometric determination of manganese in pharmacological preparations and vegetable fertilizers is proposed. The method is based on the formation of a blue coloured complex of Mn (II) with 9-phenyl-2,3,7-trihydroxy-6-fluorone (PF) in the presence of cetylpyridinium chloride (CP) and Triton X-100. Optimum concentrations of PF, CP, Triton X-100 and pH ensuring maximum absorbance were defined. The complex Mn(II)-PF-CP-Triton X-100 shows maximum absorbance at 591 nm with the molar absorptivity value 1.77x10(5 )L mol(-1 )cm(-1). The detection limit of the method is 0.004 microg mL(-1). The Beer's law is obeyed for manganese concentrations in the range 0.02-0.2 microg mL(-1). The effect of foreign ions was elucidated. The statistical evaluation of the method was carried out for six determination using 5 microg Mn and the following results were obtained: standard deviation 0.021, confidence interval 5.05+/-0.05 microg Mn. The method has been applied for the determination of manganese in pharmacological preparations (Biovital, Kinder Biovital) and vegetable fertilizers (Hydrovit 100, Florovit).