Electron spin resonance for quantitative assay of chlorpromazine in drug formulations by oxidation with cerium(IV) in sulfuric acid media

For the first time electron spin resonance (ESR) spectroscopic technique has been used for a highly selective determination of chlorpromazine. The method is based on the oxidation reaction of chlorpromazine with cerium(IV) in sulfuric acid media. In this method 3.8x10(-3) mol dm(-3) cerium(IV) was used in 0.035 mol dm(-3) sulfuric acid with the ESR spectra recorded at room temperature. A calibration equation of the following form was obtained over the linear concentration range of 10-100 ppm with a correlation coefficient (r) of 0.999: A=1.355+0.0382C. The results obtained by the ESR method were found to be comparable with those obtained by the British Pharmacopoeia (BP) method. The method suffers no interferences excipients rendering the method suitable for determination of this drug in pharmaceutical preparations.     

Sequential injection technique for automated titration: spectrophotometric assay of vitamin C in pharmaceutical products using cerium(IV) in sulfuric acid

For the first time sequential injection analysis (SIA) technique has been employed for titrimetry. A new SI titrimetric spectrophotometric method for the assay of vitamin C in drug formulations was explored. The method is based on the oxidation reaction of vitamin C with cerium(IV) in sulfuric acid media using a spectrophotometer as a detector with the wavelength monitored at 410 nm. A 2(3) factorial design chemometric approach was employed to study the interaction effect of the chemical and system variables, mainly cerium(IV), sulfuric acid concentrations and the flow rate. The results of the chemometric optimization revealed that the optimum operating conditions for the SI titrimetric analysis of vitamin C were 7.0 x 10(-3) M cerium(IV), 0.455 M sulfuric acid and 28.9 microL s-1 flow rate. A linear calibration plot for the determination of vitamin C was obtained in the concentration range between 30 to 200 ppm. The method was applied to the determination of vitamin C in pharmaceutical preparations and no excipient was found to pose any interference, thus rendering the method suitable for the determination of the drug in pharmaceutical preparations. The SIA method is found to be accurate when the results were statistically compared with the results obtained by the BP standard method. The SIA method is superior when compared to the conventional titration method, the BP standard method and previous methods with respect to precision and automation in solution handling.     

Flow injection titrimetric analysis of vitamin C in pharmaceutical products

A flow injection titrimetric method for the assay of vitamin C using cerium(IV) was developed. A 157 mul vitamin C solution was injected into a carrier stream of 7.48 x 10(-3)M cerium(IV) prepared in 0.10M sulfuric acid flowing at a rate of 5.0 ml/min. A 1.3 ml mixing chamber was employed for dispersion of the resultant solution which was propelled through a flow-through cell and detected using the spectrophotometer at a wavelength monitored at 410 nm. The method was applied to the determination of vitamin C in pharmaceutical preparations and a high accuracy was attained when compared with the British Pharmacoepeia (BP) method. Excellent precision indicated by a relative standard deviation of less than 0.9% was always obtained. No interferences were encountered and as many as 36 samples per hour were reached for throughput.     

Indirect determination of uranium by the on-line reduction and fluorimetric detection of cerium(III).

A novel flow injection method has been developed for the indirect determination of uranium by the on-line reduction and subsequent fluorimetric detection of cerium(III). A sample solution containing uranium(VI), prepared as a sulfuric acid solution, was injected into a sulfuric acid carrier solution and passed through a column packed with metal bismuth to reduce uranium(VI) to uranium(IV). The sample solution was merged with a cerium(IV) solution to oxidize uranium(IV) to uranium(VI) and the cerium(III) generated was then monitored fluorimetricaly. The present method is free from interference from zirconium, lanthanides, and thorium, and has been successfully applied to the determination of uranium in monazite coupled with an anion-exchange separation in a sulfuric acid medium to eliminate iron(III). The sample throughput was 25 per hour and the lowest detectable concentration was 0.0042 mg l(-1).     

Differential electrolytic potentiometry, a detector in flow injection analysis for oxidation-reduction reactions

For the first time, differential electropotentiometry (DEP) is coupled with the flow injection analysis (FIA) technique for detection of oxidation–reduction reactions, and is utilized for quantitative determination of vitamin C in pharmaceutical preparations using 1.0×10⁻³-M cerium(IV) in 0.50-M sulfuric acid as carrier. Two similar platinum electrodes were employed and polarized by a constant current. Optimization by the univariate method was carried out and the optimum conditions for current density, flow rate, sample size and concentration of sulfuric acid were 4 mA, 0.93 ml min⁻¹, 140 μl and 0.25 M, respectively. Vitamin C was determined in the concentration range 100–300 ppm with 0.9987 correlation coefficient and 1.9 standard deviation. The method was applied to the determination of vitamin C in pharmaceutical preparations and no excipient was found to pose any interference thus rendering the method suitable for determination of the drug in pharmaceutical preparations. The accuracy of the method was determined by comparison with the BP standard method.     

间接荧光检测离子色谱法分析维生素C、亚硫酸根和硫代硫酸根

报道了一种用离子色谱分析维生素Ｃ、亚硫酸根和硫代硫酸根离子的新方法。在这种方法中采用了四价铈柱后氧化还原反应和三价铈荧光检测法。同时也给出了使用这种方法的一些最佳的实验条件。     

Computer assisted optimization of a flow-injection method for the assay of promethazine, chlorpromazine and trimeprazine in drug formulations

A simple, accurate and fast method for the determination of promethazine, chlorpromazine and trimeprazine neuroleptics in drug formulations by flow injection spectrophotometric detection was developed. The method was based on the oxidation of the drug with potassium dichromate in sulphuric acid media. Optimum conditions were obtained by using the modified simplex computer programme. A 110-mul sample volume was taken as reasonable for all the compounds. The optimum conditions reached were 76-cm coil length, 6.00 ml/min flow rate, 3.10M sulphuric acid and 0.00167M dichromate for promethazine; 94-cm coil length, 5.00 ml/min flow rate, 1.48M sulphuric acid and 0.00185M dichromate for chlorpromethazine and 80-cm coil length, 6.00 ml/min flow rate, 3.44M sulphuric acid and 0.000500M dichromate for trimeprazine. High sample throughput of at least 200 samples per hour was obtained for all compounds. Acceptable relative standard deviations in the range +/-0.4-0.9%, and good accuracy in the range 99.5-99.9% were attained when the method was statistically compared with the BP method and when applied to proprietary drugs, without suffering interferences.     

Flow injection method for the assay of the anti-arrhythmic procainamide HCl in drug formulations utilizing statistical optimization techniques

A flow injection spectrophotometric method for the determination of procainamide HCl was explored. The method was based on the oxidation of procainamide HCl with cerium(IV) in sulphuric acid media and subsequent monitoring of the absorbance of the oxidized form of the drug at 480 nm. A sample rate of 250 samples per hour was attained. The procedure was optimized by the Factorial Design at two upper and lower levels of the five parameters sample loop size, flow rate, coil length, sulphuric acid and cerium(IV) concentrations. The latter three indicated high interactions and revealed significance to peak height value therefore optimized by the Super Modified Simplex programme. The optimized FI system with a linear calibration range of 100-600 ppm was found to be adequate and suitable for determination of procainamide HCl in proprietary drugs. A high degree of accuracy of the results was demonstrated by a statistical comparison with those obtained by the British Pharmacopoeia method of the same batch of drugs.     

Investigation of Chemiluminescence Behavior of Flavonoids with Cerium (IV)‐Rhodamine B System

Abstract

The chemiluminescence (CL) behavior of five major flavonoid types in cerium (IV)‐rhodamine B system was investigated by flow‐injection. Strong CL was observed when cerium (IV) reacted with rhodamine B in sulfuric acid medium in the presence of flavonoids. This reaction system has been established as a simple, rapid, and highly sensitive flow injection CL analysis for quercetin and kaempferol, and their detection limit (3σ) was 2.7 and 0.22 nmol/L, respectively. The relative standard deviation (n=8) was 1.2% for 1.0 µmol/L quercetin and 1.9% for 0.5 µmol/L kaempferol. This method was successfully applied to the determination of quercetin in the hydrolysate of rutin and compared well with the high performance liquid chromatography (HPLC) method. From a comparison of several related flavonoids, it was concluded that only flavonoids that contain a free 3‐hydroxyl and 2, 3‐double bond in conjugation with 4‐oxo function could produce a relatively strong CL emission.     

Determination of cerium in rare earth ores by fluorescence quenching of rhodamine 6G

A fluorescence quenching method has been developed to determine cerium with rhodamine 6G. The method is based on the oxidation of rhodamine 6G by cerium(IV) in sulfuric acid solution. The linear calibration range is 4.0 × 10^–7 -1.6 × 10^–6mol/L. The detection limit is 1.0 × 10^–7 mol/L. The relative standard deviation was 1.0% (n = 5). The method has been used to determine cerium in rare earth ores, with satisfactory results. The method offers the advantages of simplisity, sensitivity and selectivity.     

滤纸还原–硫酸铈滴定法测定含锑铅精矿中锑

建立滤纸还原-硫酸铈滴定法测定含锑铅精矿中锑含量的方法。采用硫酸、硝酸溶解样品,以滤纸作还原剂,在盐酸介质中,用磷酸掩蔽高价铁,以甲基橙和亚甲基蓝为指示剂,于80~90℃下,用硫酸铈标准溶液滴定至溶液突变至亮蓝色(铁含量高时为黄绿色)为终点。在实验条件下对3个含锑铅精矿样品进行分析,测定结果的相对标准偏差为0.7%~2.2%(n=8),加标回收率为95%~106%。分别采用该方法和锑矿石中锑的国家标准分析方法GB/T 15925-2010对含锑铅精矿样品进行测定,两种方法的测定值基本一致,相对误差为1.4%~4.5%。该方法准确度高,精密度好,成本低,适用于铅精矿中锑含量的测定。     

A new oxidimetric reagent: potassium dichromate in a strong phosphoric acid medium--VII. Photometric titration of vanadium(IV) and of cerium(III) alone and in mixtures with iroN(II)

Vanadium(IV) can be accurately titrated with potassium dichromate in media containing phosphoric acid of 3-12M concentration: the change in absorption of vanadium(IV) is followed in the region 660 mmicro using a red filter. It is more convenient to carry out the titration in 3M phosphoric acid because at higher concentrations chloride, nitrate, cerium(III) and manganese(II) may interfere. Photoelcetric titration is more convenient than potentiometric because the former can be made in a 3M phosphoric acid medium, whereas the latter is possible only in 12M phosphoric acid. The simultaneous differential photometric titration of iron(II) and vanadium(IV) is also possible. Conditions have been found for the photometric titration of cerium(III) and of cerium(III) plus iron(II). The titration is carried out (at 450 mmicro or with a blue filter) in about 10.5M phosphoric acid. Application of the method to a cerium mineral is considered.     

Oxidation of cerium(III) to cerium(IV) using a mixture of hot concentrated perchloric and sulfuric acids

The oxidation of cerium(III) to cerium(IV) using a hot concentrated mixture of perchloric and sulfuric acids is shown to be quantitative Optimum conditions for the oxidation are described Complete removal of chlorine, an interfering decomposition product of boiling perchloric acid, is achieved by purging the concentrated acid solution with nitrogen before dilution with water The presence of sulfuric acid is essentral, the chief role of sulfuric acid apparently being to stabihze the cerium(IV) as a sulfatocerate complex.     

Spectrophotometric determination of cerium(IV), arsenic(III), and nitrite with promazine hydrochloride

Promazine hydrochloride is proposed as a new reagent for the spectrophotometric determination of cerium(IV), arsenic(III), and nitrite. The reagent forms a red-colored radical with cerium(IV) instantaneously in 0.5?2 M sulfuric acid or 0.5?2.5 M phosphoric acid solution. The red radical exhibits maximum absorbance at 505 nm. An 11-fold molar excess of the reagent is necessary for the full development of the color intensity. Beer's law is valid over the concentration range 0.5–15 ppm in sulfuric acid and 0.5–21 ppm in phosphoric acid. The sensitivities of the reaction in sulfuric and phosphoric acid media are 0.022 and 0.019 μg/cm², respectively. The effects of acidity, time, order of addition of reagents, temperature, reagent concentration, and diverse ions are reported. The proposed method offers the advantages of good sensitivity, simplicity, rapidity, selectivity, and a wider range of determination without the need for extraction. Arsenic(III) and nitrite are indirectly determined.     

Sensitive determination of phenolic compounds using high-performance liquid chromatography with cerium(IV)-rhodamine 6G-phenolic compound chemiluminescence detection

A simple, selective and sensitive determination method of 20 phenolic compounds has been developed using high-performance liquid chromatography (HPLC) with chemiluminescence detection. The method is based on the chemiluminescent enhancement by phenolic compound of the cerium(IV)-rhodamine 6G system in sulfuric acid medium. Twenty phenolic compounds were separated on a XDB-C(8) column with a gradient elution using a mixture of methanol and 1.0% acetic acid as a mobile phase. Under the optimized conditions, a linear working range extends 2 orders of magnitude with the relative standard deviations of intra- and inter-day precision below 4.0%, and the detection limits (S/N = 3) were in the range of 1.5-82.1 ng/ml. The chemiluminescence reaction was compatible with the mobile phase of high-performance liquid chromatography. The proposed method has been successfully applied to the assay of phenolic compounds in red wine without any pretreatment.     

Simultaneous determination of quercetin, kaempferol, and isorhamnetin in phytopharmaceuticals of Hippophae rhamnoides L. by high-performance liquid chromatography with chemiluminescence detection

A novel method based on reversed-phase high-performance liquid chromatography with chemiluminescence detection has been developed for the simultaneous determination of three flavonols including quercetin, kaempferol, and isorhamnetin. The procedure was based on the chemiluminescent enhancement by flavonols of the cerium(IV)-rhodamine 6G system in sulfuric acid medium. The effects of several parameters on the HPLC resolution and CL emission were studied systematically. Good separation was achieved with isocratic elution using a mixture of methanol and aqueous 1.0% acetic acid (37:63, v/v) within 25 min. Under optimized conditions, the linear working range covers 3 orders of magnitude with relative standard deviations below 4.5% for 11 replicate injected flavonol samples, and detection limits (S/N= 3) were 1.6 x 10(-8), 3.5 x 10(-9), and 6.5 x 10(-9) g mL(-1) for quercetin, kaempferol, and isorhamnetin, respectively. The chemiluminescence reaction was compatible with the mobile phase of high-performance liquid chromatography. The proposed method has been successfully applied to the determination of three active flavonols in phytopharmaceuticals of Hippophae rhamnoides L. After a simple extraction procedure, the repeatability and recovery were satisfactory.     

Spectrofluorimetric Determination of Antimony

Abstract

A spectrofluorimetric procedure for the determination of micromolar concentrations of antimony(III) was devised based on its reduction of cerium(IV) to produce fluorescent cerium(III). The method was optimized and the reaction was fast enough in hydrochloric acid media without the need for iodide or osmium(VIII) as catalysts. Linear calibration graphs were obtained in the range 1-10 10^?6M. The standard deviation for determining 5 × 10^?6M antimony(III)(10 times) was 1.43 × 10^?7M and the relative error was -3.4 %. The method was applied to the determination of antimony(III) in its mixture with antimony(V), total antimony was later determined after reduction with mercury metal in deoxygenated solutions. The affect several reducing agents on the determination of antimony-was also examined.     

还原性负离子的间接荧光检测离子色谱法

采用４个铈柱后反应和３价铈荧光检测的离子色谱法分离维生素Ｃ,亚硝酸根,硫代硫酸根,亚硫酸根,草酸根和碘离子６种还原性负离子,同时也给出了使用这种方法的一些最佳条件。     

Spectrofluorometric determination of ketorolac tromethamine via its oxidation with cerium(IV) in pharmaceutical preparations and biological fluids

A simple and sensitive fluorometric method for determination of ketorolac tromethamine was studied. The method depends on oxidation of the drug with cerium(IV) and subsequent monitoring of the fluorescence of the induced cerium(III) at lambda(em) 365 nm after excitation at 255 nm. Different variables affecting the reaction conditions, such as the concentrations of cerium(IV), sulfuric acid concentration, reaction time, and temperature, were carefully studied and optimized. Under the optimum conditions, a linear relationship was found between the relative fluorescence intensity and the concentration of the investigated drug in the range of 0.1-0.8 microg/mL. No interferences could be observed from the excipients commonly present in dosage forms. The proposed method was successfully applied to the analysis of the investigated drug in its pure form, pharmaceutical preparations, and biological fluids with good accuracy and precision. The recoveries for pharmaceutical formulations ranged from 99.8-101.0 +/- 0.6% for tablets, 98.5-101.0 +/- 1.0% for ampoules, and 99.0-100.5 +/- 0.7% for eye drops. The results obtained by the proposed method were satisfactory compared with those obtained by the official method. The recoveries for biological fluids were 99.1-100.4 +/- 0.7 and 99.0-100.0 +/- 0.5% for plasma and urine, respectively.