Rapid, low level determination of silver(I) in drinking water by colorimetric-solid-phase extraction

A rapid, highly sensitive two-step procedure for the trace analysis of silver(I) is described. The method is based on: (1) the solid-phase extraction (SPE) of silver(I) from a water sample onto a disk impregnated with a silver-selective colorimetric reagent, and (2) the determination of the amount of complexed analyte extracted by the disk by diffuse reflectance spectroscopy (DRS). This method, called colorimetric-solid-phase extraction (C-SPE), was recently shown effective in determining low concentrations (0.1-5.0 mg/ml) of iodine and iodide in drinking water. This report extends C-SPE to the trace (∼4 μg/l) level monitoring of silver(I) which is a biocide used on the International Space Station (ISS). The determination relies on the manually driven passage of a water sample through a polystyrene-divinylbenzene disk that has been impregnated with the colorimetric reagent 5-(p-dimethylaminobenzylidene) rhodanine (DMABR) and with an additive such as a semi-volatile alcohol (1,2-decanediol) or nonionic surfactant (Brij 30). The amount of concentrated silver(I) is then determined in a few seconds by using a hand-held diffuse reflectance spectrometer, with a total sample workup and readout time of ∼60 s. Importantly, the additive induces the uptake of water by the disk, which creates a local environment conducive to silver(I) complexation at an extremely high concentration factor (∼800). There is no detectable reaction between silver(I) and impregnated DMABR in the absence of the additive. This strategy represents an intriguing new dimension for C-SPE in which additives, directly loaded in the disk material, provide a means to manipulate the reactivity of the impregnated reagent.     

EGCG在Tween80胶束体系中的性质(英文)

通过离子萃取技术,从黄山绿茶中提取高纯度儿茶素没食子酸酯(EGCG).在Tween 80/EGCG/H2O体系中,随着EGCG浓度增加,Tween 80临界胶束浓度和胶束动力学半径增大;随着Tween 80浓度增加,EGCG和Tween 80扩散系数减小,而EGCG的紫外-可见吸收光强度和荧光强度增加.对EGCG在Tween 80胶束中的定位也进行了讨论.     

低分子烃类对吐温80-盐-水液-固析相分离的影响

报导了环己烷、庚烷等的加溶对非离子表面活性剂（吐温－80）液－固析相分离的影响,使小分子显色剂对甲酰基偶氮变色酸（CApF)、偶氮胂1（ArsenazoI)和配合物在低温下就易从盐水溶液相富集到表面活性剂固相,萃取率达95％。并对不己烷、庚烃的加溶机理及温度的作用做了探讨。     

非离子表面活性剂TWeen80相图的研究

本文研究了醇类（正丁醇、正戊醇、正辛醇和正癸醇）、油类（正十八烷、正十六烷、正十四烷、正十烷、正癸烷和正辛烷）、正十八烷含量以及NaCl浓度对Tween80／醇／油／水体系相图的影响。结果表明，NaCl浓度对Tween80／正辛醇／正十八烷／水体系相图的影响不明显；醇类随着炭原子数目的增加，O／W微乳液区面积增大，W／O微乳液区面积减小，微乳液区总面积增大；不同的油类形成的微乳液区面积由大到小的顺序是：正十六烷≈正十四烷＞正十二烷＞正癸烷＞正十八烷＞正辛烷；随着正十八烷含量的增加，微乳区面积减小。用2277热活性检测系统测定了石油菌B－2分别在非微乳液和助表面活性剂分别是正戊醇、正辛醇，油是正十八烷所形成的微乳液中生长的功率－时间曲线。结果表明微乳液培养基更适用于B－2利用高碳烷烃进行生长；正辛醇作助表面活性剂形成的微乳液培养基比正戊醇作助表面活性剂形成的微乳液培养更为有利；O／W型微乳液比W／O型微乳液对B－2的生长更为有利。     

Influence of Tween 80 on lipid metabolism of an Aspergillus niger strain

Addition of 0.1% of nonionic surface-active Tween 80 to a medium optimized for pectolytic enzyme production of Aspergillus niger increased the amount of enzymes excreted by 70%. In the presence of Tween 80 the amount of sterol esters and triacylglycerols was increased. During the course of cultivation the amounts of precursors for ergosterol biosynthesis diminished with an increase of ergosterol. A. niger incorporated cholesterol from the medium, partly converting it to cholesterol esters. Sterol esters were formed only with selected fatty acids. Oleic acid, the hydrophobic part of Tween 80, was mainly incorporated in phospholipids and glycolipids.     

Kinetic spectrophotometric determination of hydrazine

A sensitive kinetic method for determining low levels of hydrazine has been described. The method is based on the measurement of the rate of the reaction between hydrazine and Mo(VI) in the presence of hydrochloric acid. The redox reaction was monitored spectrophotometrically at 710 nm. The variable-time and fixed-time methods were used. The calibration graph was linear for hydrazine concentrations of 1.0 × 10⁻⁴-1.4 × 10⁻² M, using the fixed-time method of analysis. The method is simple, rapid, precise, sensitive and widely applicable.     

吐温80—AuCl4^—化学发光新体系测定痕量碘离子的研究

基于碘离子对吐温８０－ＡｕＣｌ４＾－体系化学发光的强烈抑制作用,提出了一种测定痕量碘离子的新的化学发光分析法。方法的线性范围和检测分别为１．２×１０＾－８￣１．０×１０＾－６ｇ／ｍＬ和５．１×１０＾－９ｇ／ｍＬ碘离子。拟定的方法体系简单,选择性好,加碘酱油和实际水样中碘离子的测定,结果满意。     

FTIR study of Tween80/1-butyl-3-methylimidazolium hexafluorophosphate/toluene microemulsions

With the aid of Tween80, an environmentally benign nonionic surfactant applied to medicine and food industry, the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF₆) formed IL microemulsions with toluene. The phase diagram of the ternary system was prepared at 25 °C. It was demonstrated that there were a single-phase region and a multiple phase region in the ternary phase diagram. The single-phase region could be further divided into toluene-in-bmimPF₆, bicontinuous, and bmimPF₆-in-toluene microemulsion regions by electrical conductivity. In particular, the microstructural characteristics of the microemulsions were investigated by Fourier transform infrared spectroscopy. The results indicated that it was the hydrogen-bonded interactions between bmimPF₆ and Tween80 that might be the driving force for the solubilization of bmimPF₆ into the core of the Tween80 aggregates.     

动力学光度法测定痕量甲醛

在稀硫酸溶液中,甲醛对KClO3氧化罗丹明6G褪色反应有催化作用,研究了其动力学条件,建立了测定痕量甲醛的动力学光度分析方法,线性范围为0.02～1.8μg/mL,检出限为1.5×10-8g/mL。该法用于湖水、饮料和漆料中痕量甲醛的测定,标准加入回收率为93.8%～108.5%,RSD为2.6%～3.4%。     

Study on the Polarity of bmimPF6/Tween80/toluene Microemulsion Characterized by UV-Visible Spectroscopy

With the aid of nonionic surfactant Tween80, the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF₆) forms nonaqueous microemulsions with toluene. The phase diagram of the ternary system was prepared at 25°C. It was demonstrated that there were a single-phase region and a two-phase region in the ternary phase diagram. The single-phase region could be further divided into toluene-in-bmimPF₆, bicontinuous and bmimPF₆-in-toluene microemulsion regions by electrical conductivity. And by the use of methyl orange as an absorption probe, the polarity of the bmimPF₆-in-toluene microemulsion was probed by UV-vis spectroscopy. A relatively constant polarity of the microemulsion droplets is obtained in the bmimPF₆ microemulsion.     

靛蓝胭脂红-溴酸钾体系催化光度法测定微量碘

研究了在室温及0．4mol/L H2SO4介质中碘离子对KBrO3氧化靛蓝胭脂红褪色反应的催化作用,建立了一种测定微量碘的新方法。碘离子浓度在0．20－2．0μg/mL范围内与△A呈线性关系,检测限为0．14μg/mL。多数常见离子无干扰。可用于海带中微量碘的测定。     

Chemiluminescence Determination of Sulpiride in Pharmaceutical Preparations and Biological Fluids Based on KMnO4‐Tween 80 Reaction

Chemiluminescence (CL) of an acidic KMnO₄ system in the presence of Tween 80 was investigated for the determination of sulpiride. Strong CL was recorded when a mixture of sulpiride and Tween 80 was injected into acidic KMnO₄ solution. The experimental parameters affecting the CL intensity were carefully studied using flow injection mode. Under the optimum conditions, the CL intensity was proportional to the concentration of sulpiride in the range of 5.0 × 10⁻⁷ ∼ 1.0 × 10⁻⁴ g mL⁻¹. The detection limit is 1.6 × 10⁻⁷ g mL⁻¹ sulpiride, and the relative standard deviation for 1.0 × 10⁻⁶ g mL⁻¹ sulpiride solution is 1.5% (n = 11). The proposed method has been successfully applied to the determination of sulpiride in tablets and in spiked human plasma and urine samples.     

Kinetic Effects in non Ionic Micellar Solutions

The elimination reaction between 2-(p-nitrophenyl)ethyl bromide and OH^- ions was studied in nonionic aqueous micellar solutions of two esters of long chain fatty acids and sorbitan polyethylene glycol, Tween 20 (monolaurate) and Tween 80 (monooleate). The equilibrium binding constants of the 2-(p-nitrophenyl)ethyl bromide molecules to the nonionic micellar aggregates were obtained by spectroscopic measurements. The experimental kinetic data were quantitatively rationalized by the treatment of first-order reactions based on the pseudophase model. Results from this work and from previous studies show that, whereas the presence of cationic and sulfobetaine micelles accelerates the reaction, the presence of nonionic micelles inhibits the reaction.     

Kinetic spectrophotometric determination of bromide in clidinium-c drug

A simple,rapid and sensitive method has been described for the determination of the trace amounts of bromide.The method is based on the catalytic effect of bromide ion on the oxidation of methylene blue by bromate in sulfuric acid media.The reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of methylene blue at 665 nm. Bromide was determined in the range of 0.05-1.90μg/mL with the detection limit of 0.03μg/mL.The relative standard deviations of five replicate determinations of 0.20 and 10.0μg/mL of bromide were 2.4%and 1.8%,respectively.The influence of potential interfering ions and substances was studied.The method is applied to the analysis of bromide in clidinium-c tablet as a real sample.     

Focused microwaves-assisted extraction and simultaneous spectrophotometric determination of vanillin and p-hydroxybenzaldehyde from vanilla fragans

A new method to quick extraction of vanillin and p-hydroxybenzaldheyde (PHB) of vanilla beans from vanilla fragans is proposed. Samples were irradiated with microwaves energy to accelerate the extraction process and photometric monitoring was performed at 348 and 329 nm (vanillin and PHB, respectively). The simultaneous determination of vanillin and PHB from extracts was performed using the Vierordt's method, which showed a precision, expressed as relative standard deviation, smaller 2.5% for both analytes. Conditions such as microwaves irradiation power, number of irradiation and non-irradiation cycles, irradiation time and ethanol concentration were optimized by means of multivariate screening that showed that irradiation power and number of irradiation cycles are the most significant condition in the vanilla extraction process. The focused microwave-assisted extraction (FMAE) was applied to commercial (dried vanilla beans from fresh green vanilla beans), lyophilised and dried (commercial vanilla dried at 135 °C in oven) vanilla beans samples. The results showed that the extraction of vanillin and PHB in the commercial vanilla samples were higher than in dried and lyophilised samples. With the proposed FMAE a decrease in the extraction time of 62 times and an increase in the vanillin and PHB concentrations between 40 and 50% with respect to the official Mexican extraction method, were obtained.     

Kinetic spectrophotometric determination of amodiaquine and chloroquine

Abstract  Two simple, sensitive, and selective spectrophotometric methods were developed for determining amodiaquine (AQ) and chloroquine (CQ) based on their oxidation with potassium iodate and potassium bromate, respectively. The initial rates of oxidation of AQ and CQ were monitored at 342 and 343 nm, the wavelengths of maximum absorptions of the two drugs. The various experimental parameters affecting oxidation reactions were thoroughly studied and optimized. Beer’s law was obeyed for 0.2–4.0 and 0.5–5.0 μg cm⁻³, with correlation coefficients of 0.9999 and 0.9998 (n = 6) and a detection limit (based on the 3S _b -criterion) of 0.04 and 0.06 μg cm⁻³ for AQ and CQ. The proposed methods were conveniently applied to determining AQ and CQ in pure and dosage forms. Graphical abstract        

Interaction of cationic chlorin photosensitizers with non-ionic surfactant Tween 80

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Kinetic spectrophotometric determination of certain cephalosporins using oxidized quercetin reagent

A simple, precise and accurate kinetic spectrophotometric method for determination of cefoperazone sodium, cefazolin sodium and ceftriaxone sodium in bulk and in pharmaceutical formulations has been developed. The method is based upon a kinetic investigation of the reaction of the drug with oxidized quercetin reagent at room temperature for a fixed time of 30 min. The decrease in absorbance after the addition of the drug was measured at 510 nm. The absorbance concentration plot was rectilinear over the range 80–400 μg mL⁻¹ for all studied drugs. The concentration of the studied drugs was calculated using the corresponding calibration equation for the fixed time method. The determination of the studied drugs by initial rate, variable time and rate-constant methods was feasible with the calibration equations obtained but the fixed time method has been found to be more applicable. The analytical performance of the method, in terms of accuracy and precision, was statistically validated; the results were satisfactory. The method has been successfully applied to the determination of the studied drugs in commercial pharmaceutical formulations. Statistical comparison of the results with a well established reported method showed excellent agreement and proved that there is no significant difference in the accuracy and precision.     

Kinetic resolution of cyanohydrins via enantioselective acylation catalyzed by lipase PS-30

By using lipase PS-30 as catalyst, the kinetic resolution of a series of racemic cyanohydrins has been achieved via enantioselective acylation. The values of kinetic enantiomeric ratio (E) reached up to 314. Substituent effect is also briefly discussed.     

Potentiometric and spectrophotometric pKa determination of water-insoluble compounds: validation study in a new cosolvent system

In this paper the validation of pK_a determination in MDM-water mixtures is presented. The MDM-water mixture is a new multicomponent cosolvent mixture (consisting of equal volumes of methanol, dioxane and acetonitrile, as organic solvents) that dissolves a wide range of poorly water-soluble compounds. The cosolvent dissociation constants (p_sK_a) of 50 chemically diverse compounds (acids, bases and ampholytes) were measured in 15-56 wt% MDM-water mixtures by potentiometric or spectrophotometric titration and the aqueous pK_a values obtained by extrapolation. Three different extrapolation procedures were compared in order to choose the best extrapolation in MDM-water mixture using a sub-set of 30 water-soluble compounds. The extrapolated results are in good agreement with pK_a values measured in aqueous medium. No significant difference was found among these extrapolation procedures thus the widely used Yasuda-Shedlovsky plot was proposed for MDM cosolvent also. Further we also present that the single point estimation based on measurement in 20%/v MDM-mixture using a general calibration equation may be suitable for rapid pK_a determination in the early phase of drug research.