Determination of critical micelle concentration values by capillary electrophoresis

An improved, simple capillary electrophoresis method for the determination of critical micelle concentration values in an easy way by plotting the corrected electric current values versus the surfactant concentrations at a given field was described. The critical micelle concentrations of sodium dodecyl sulfate in different solutions were obtained, and the values were in good agreement with those found in the literature. The text was submitted by the authors in English.     

Sustainable Synthesis of the Naturally Hypolipidemic Agent α-Asarone

A short and practical preparation of α-asarone was developed using the inexpensive methylisoeugenol as a starting material. The utilization of a sequence of tribromination, debromination, and copper-mediated aromatic substitution enabled the stereoselective formation of only the E-isomer of α-asarone in good yield.     

用GC－MS法测定尿中可待因及其代谢物的浓度

建立了用ＧＣ－ＭＳ（ＳＩＭ）内标定量法快速测定人尿中可待因及其代谢物浓度的方法。样品经酸水解、乙醚／异丙醇提取，用ＭＳＴＦＡ－ＭＢＴＦＡ衍生化后进样于ＧＣ－ＭＳＤ，方法灵敏、准确，可用于监测吸毒者尿中可待因、吗啡类药物的浓度。本法已经受ＩＯＣ的１９９２年水平考试的考验。     

Determination of ambroxol hydrochloride in tablets using flow-injection UV spectrophotometry and HPLC

A flow-injection UV spectrophotometric method was developed for the determination of ambroxol hydrochloride in tablets. The quantitative determination of ambroxol was performed at 245 nm using distilled water as the carrier solvent. In this study, the flow rate, loop volume, and the number of injections per hour were 15 mL/min, 193 μL, and 100, respectively. The analytical signal of ambroxol was linear in the concentration range of 40–200 μg/mL. The detection limit and limit of quantification were found as 11.55 and 38.49 μg/mL, respectively. The results for the determination of ambroxol in tablets, 29.99 ± 0.23 mg (mean ± SD), were in good agreement with the labeled quantities (30 mg/tablet). A relatively high recovery value (100.4%) shows the accuracy of the proposed method. Furthermore, the results obtained were in accordance with those obtained by the HPLC method, which were used as a comparison method for the determination of ambroxol HCl, as far as the Student’s t-test and Fisher test results were concerned. It was concluded that the proposed flow-injection UV spectrophotometric method was fast, accurate, precise, and suitable for automation in the determination of ambroxol. The text was submitted by the authors in English.     

New computational approach for the simultaneous photometric determination of catalysts and activators

A new method for the simultaneous kinetic determination of catalysts and activators was developed on the basis of a mathematical model. The parameters and variables are optimized from experimental data obtained by application of a multiple standard-addition method and use of the Gauss-Newton and Simplex method, both of which provide identical results. The proposed method was applied to the simultaneous photometric determination of Mn(II) and Pb(II) on the basis of their catalytic and activating effects, respectively, on the oxidation of Tiron by hydrogen peroxide. Data were both acquired and processed with the aid of software developed by the authors. The linear determination range achieved was 1.00-5.00 ng/ml Mn(II) and 200-800 ng/ml Pb(II). Experimental readings were made at 450 nm with a fibre optics detector. The most serious interference with the method was posed by Cr(III).     

Determination of sulfur in cosmetic products using ion-selective electrode

A method for the indirect voltammetric determination of sulfur is proposed. A solution of hydrazine hydrate was used as an alkaline medium to transform sulfur into sulfide. The optimal conditions were chosen for sulfur determination using ion-selective electrode and the results agree with those obtained by high-performance liquid chromatography. The text was submitted by the authors in English.     

KBrO3-KBr紫外分光光度法测定痕量苯酚

研究了在盐酸介质中以 KBrO3-KBr 紫外分光光度法测定痕量苯酚的条件,在浓度为 0.6mol/L HCl,3×10-5mol/L KBrO3,5×10-4mol/L KBr,6×10-4mol/L KI 溶液中测定苯酚时,线性范围为 0.10～2.5mg/L,表观摩尔吸光系数为 1.89×104L·mol-1·cm-1,Sandell 指数为 4.98μg/cm2.本法已用于测定废水中苯酚.     

Simultaneous First-Derivative Spectrophotometric Determination of Nickel and Manganese Complexes with 2-(2-Pyridylmethyleneamino)phenol

Abstract

A method is proposed for the simultaneous determination of nickel and manganese by first-derivative spectrophotometry based on their reactions with 2-(2-pyridylmethyleneamino)phenol (PMAP) Schiff base. The method allows the determination of Ni and Mn in the concentration range 0.3–3.0 μg ml^?1 in mixtures with their ten-fold concentration ratio. The method has been applied for Ni and Mn determination in bronzes. To optimize the experimental conditions for spectrophotometric determination of Mn with PMAP stability constants at different pH values have been determined. A critical evaluation of the proposed method was performed by statistical analysis of the experimental data.     

Diphenyl carbazone as an internal indicator in volumetric analysis

Summary A method for the volumetric determination of calcium using diphenyl carbazone as indicator has been described. Calcium is precipitated by excess sodium oxalate, the excess oxalate being determined by standard lead nitrate. A study of the possible interferences of barium and magnesium in the above determination is undertaken and it is shown that the above procedure is applicable to the determination of calcium in the presence of magnesium and barium.Sincere thanks of the authors are due to Professor G. B. Singh for providing the necessary facilities during the course of the above investigation.     

The micro-volumetric determination of lead with thionalide and its application to the analysis of tin-base and lead-base alloys

The authors have elaborated an exact micro-volumetric method for the determination of lead with thionalide. The method has been successfully applied to the determination of lead in tin-base and lead-base alloys, following the isolation of lead as lead sulphate and its redissolution in ammonium acetate.     

Determination of parabens in pharmaceutical and cosmetic products by capillary electrophoresis

A validated capillary electrophoresis method for the determination of parabens-methyl, ethyl, propyl, and butyl is described. The optimum results were obtained by the use of a run buffer containing 20 mM borate buffer (pH 9.0) with 10% methanol and by applying a voltage of 20 kV, a low hydrodynamic injection of 10 s, and detecting the signals at 200 nm. Moxifloxazin was used as an internal standard. All parabens were separated within 10 min. The method showed a good repeatability, linearity, and sensitivity. It was applied to the determination of parabens in pharmaceutical and certain cosmetic products. The text was submitted by the authors in English.     

AQbD-Oriented Development of a New LC Method for Simultaneous Determination of Telmisartan and Its Impurities

Analytical quality by design (AQbD)-oriented liquid chromatographic method development for determination of telmisartan and its impurities A, C, and 1 is determination is presented. Step-by-step process was conducted in order to define reliable design space. At the beginning, critical process parameters with the highest influence on method performance were defined: acetonitrile content in the first (ACN 1) and second (ACN 2) gradient step and time (t ₂) the second gradient step. These factors were varied according to Box–Behnken plan of experiments and their influence on retention times of impurities A and C, S value between telmisartan and impurity 1 and peak capacity were followed. In this way, the relationship between the critical process parameters and critical quality attributes was established. The obtained mathematical models and Monte Carlo simulations were used to identify the design space. Fractional factorial design was applied for experimental robustness testing, and the method was validated to verify the adequacy of selected optimal conditions. Finally, all validation parameters were tested, and adequacy of the method was confirmed. Applicability as a routine method was confirmed by analysis of commercially available tablets.     

Oxidative stress increases 6-nitronorepinephrine and 6-nitroepinephrine concentrations in rat brain

6-Nitronorepinephrine (nitroNE) and 6-nitroepinephrine (nitroE) are reaction products of nitric oxide and norepinephrine and epinephrine, respectively. The authors have previously reported a method for determination of nitroNE and nitroE in rat brain using high-performance liquid chromatography-peroxyoxalate chemiluminescence reaction detection. In this study, the effect of oxidative stress on nitroNE and nitroE concentrations in rat brain was examined using this method. After kainic acid administration in rats for 2 days, the concentrations of both nitroNE and nitroE in rat brains were found to have increased by 400-600%, which was partly suppressed by the co-administration of a superoxide dismutase mimetic. This indicates that oxidative stress might increase nitroNE and nitroE concentrations in rat brains.     

Analysis of diphenylamine and impurities using monolithic column with electrochemical detection

A high-performance liquid chromatographic (HPLC) method with electrochemical detection (ED) using a monolithic column was developed and validated for the simultaneous quantitative determination of aniline, 2-aminobiphenyl, and 4-aminobiphenyl in diphenylamine samples. The proposed HPLC method provides a shorter analysis time as compared to previously reported ones (less than 4 min). Method validation was performed in terms of sensitivity, repeatability, linearity, accuracy, detection limit, and quantification limit. It is found that the method has high accuracy and precision. The limits of detection obtained were 0.23 ng/mL for aniline and 0.30 ng/mL for 2-aminobiphenyl, 4-aminobiphenyl, and diphenylamine. All authors contributed equally to this work. The text was submitted by the authors in English.     

Spectrofluorometric Determination of Thiamin and Riboflavin in Vegetable Foods

Abstract

Modifications of the AOAC thiamin and riboflavin methods allow effective and simple determination of both vitamins from aliquots of the digested sample of vegetable foods. Study of the minimum amount required for a complete hydrolysis of the vitamers corresponding to each vitamin have been carried out. A critical study of thiocrome formation which was later used in the spectrofluorimetric determination of thiamin was done. In order to separate riboflavin from the digested sample, a new liquid chromatographic method based on adsorption in florisil is proposed. The aforementionated methods were applied to different samples of several vegetable foods.     

In Process Citation

The reversibility of the determination reaction is the most frequent cause of deviations from linearity of thermometric titration curves. Because of this, determination of the equivalence point by the tangent method is associated with a systematic error. The authors propose a relationship which connects this error quantitatively with the equilibrium constant. The relation, verified experimentally, is deduced from a mathematical study of the thermograms and could probably be generalized to apply to other linear methods of determination.     

示波极谱滴定法测定生物碱氢溴酸盐类药物

以ＡｇＮＯ３作滴定剂，ＫＮＯ３和磺基水杨酸为极谱底液，采用交流示波极谱滴定法测定氢溴酸山莨菪碱、氢溴酸东莨菪碱、氢溴酸加兰他敏三种生物碱氢溴酸盐类药物的含量。该法到目前为止未见报道，具有快速、准确、终点直观的特点。     

Voltammetric determination of mesotrione at hanging mercury drop electrode

A study of the electrochemical reduction of the mesotrione pesticide on a hanging mercury drop electrode (HMDE) was performed as a basis for the development of a sensitive analytical method for natural samples. The electrochemical characteristics of herbicide mesotrione dissolved in a phosphate buffer (pH 7.0) have been determined by means of electrochemical techniques such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV) over a wide range of pH from 2.0 to 10.0. The experimental parameters, such as electrolyte type and its pH, pulse amplitude, and scan rate were optimized. The method was applied to the determination of the pesticide in a spiked soil samples. Using this method, a linear calibration curve for mesotrione was obtained up to the 0.1 μM range in pH 7 phosphate buffer solution with a detection limit (S/N = 3) of 50 nM. The method can be applied successfully to the determination of mesotrione in soils. The text was submitted by the authors in English.     

Kinetic-spectrophotometric determination of Sb(V) based on its reaction with iodide in the presence of methylene blue

A rapid, simple, and sensitive kinetic method is developed for the determination of trace amounts of Sb(V). The method is based on the reaction of Sb(V) with iodide in acidic media in the presence of methylene blue. The reaction was monitored spectrophotometrically by measuring the decrease in the absorbance at 664 nm by a fixed-time technique of 60 s. The method allowed the determination of Sb(V) at concentrations between 0.01 and 2.2 μg/mL. The limit of detection was 0.006 μg/mL and the relative standard deviation for ten replicate measurements of 0.5 μg/mL Sb(V) was 1.2%. The method was applied to the determination of Sb(V) in tap water and spring water with satisfactory results. The text was submitted by the authors in English.     

Determination of trace titanium with titanium(IV)-(DBC-arsenazo)-potassium bromate system by catalytic-kinetic spectrophotometry

In a 0.080 M sulphuric acid medium, trace titanium(IV) catalyzes the discoloring reaction of DBC-arsenazo oxidized by potassium bromate and the discoloring degree is proportional to the concentration of titanium(IV) in the solution. A new catalytic-kinetic spectrophotometric method for the determination of trace titanium(IV) was developed based on this principle. At a wavelength of 516 nm, the linear range of determination of titanium(IV) is 0–2.2 μg/25 mL. The detection limit for the determination of titanium is 2.04 ng/mL. The present method has been satisfactorily applied to the determination of titanium in fish samples. The text was submitted by the authors in English.