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.     

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.     

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 optimization of a flow injection spectrophotometric method for the assay of chlorpromazine in pharmaceutical preparations

A new simple flow injection spectrophotometric method for the assay of chlorpromazine using cerium(IV) in sulfuric acid media was developed. The oxidized form of the drug was monitored at the maximum absorbance of 526 nm. The optimum conditions were 0.035M sulfuric acid, 3.80 x 10(-3)M cerium(IV), flow rate 4.85 ml/min, coil length 45 cm and sample size 110 mm(3). Optimization was carried out by the modified simplex method. Response surface methodology was employed to investigate the ruggedness of the method. A sampling frequency of 120 hr(-1) was attained. Relative standard deviations for standard sample were usually less than 0.75. The method was applied to the determination of chlorpromazine in proprietary drugs and results were statistically compared with the official British Pharmacopoeia (BP) method.     

Sequential Injection Method for the Determination of Oxprenolol in Pharmaceutical Products Using Chemometric Methods of Optimization

A sequential injection (SI) spectrophotometric method for the determination of oxprenolol in pharmaceutical products was developed. The method is based on the oxidation of oxprenolol on-line with Ce(IV) in sulfuric acid medium and the subsequent monitoring of the absorbance of the oxidized form of the drug at 480 nm. The procedure was optimized by the orthogonal array design at two and four levels. The factors included in the optimization were Ce(IV) concentration, sulfuric acid concentration, and the stop time of the composite zone at the reaction coil. The optimized SI system with a linear dynamic range of 50–400 ppm was found to be suitable for the assay of oxprenolol in pharmaceutical products.     

Determination of isoniazid in drugs

A titrimetric method is described for the determination of isoniazid in pharmaceutical preparations. Samples are treated with an excess of iodine monochloride, and the iodine produced is titrated with iodine trichloride to an Andrews end-point. p-Aminosalicylic acid undergoes only nuclear iodination and does not interfere. Mixtures of isoniazid with vitamin C or methionine are analysed by first titrating both compounds by the Andrews method and then determining either vitamin C alone by titration with iodine monochloride or methionine by a second Andrews titration after destruction of isoniazid with nitrous acid. In both cases, isoniazid is obtained by difference. A mixture of isoniazid, methionine and vitamin C can also be analysed.     

FT-IR Spectrophotometric Analysis of Ascorbic Acid and Biotin and their Pharmaceutical Formulations

Abstract

Fourier transform–infrared (FT-IR) spectrometry was used for the rapid, direct measurement of ascorbic acid (vitamin C) and biotin (vitamin H) in different pharmaceutical products. Conventional KBr spectra were compared for the best determination of active substances in drug preparations. The Beer–Lambert law and chemometric approaches were applied in data processing.     

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.     

Factorial design and response surface optimization of spectrophotometric sequential injection analysis of olanzapine formulations

A new spectrophotometric sequential injection analysis (SIA) method for the assay of olanzapine in pharmaceutical formulations was optimized by the factorial design and the response surface approaches. The method was based on the oxidation of olanzapine by an excess amount of permanganate in sulfuric acid media. The reduction of permanganate was spectrophotometrically detected at 570 nm. The 2³ full factorial design was adopted for the optimization of permanganate concentration, sulfuric acid concentration and flow rate. The method was validated based on the IUPAC guidelines. Real pharmaceutical samples were subjected to the proposed SIA method and the results were in satisfactory agreement with those obtained by a previous spectrophotometric method. The full-automation of SIA empowered the proposed method with high repeatability (RSD 1.74%, n = 7) and intermediate-precision (RSD 2.53%, n = 5). Additionally, both automation and miniaturization offered high sampling frequency (26 samples/h). Furthermore, the employment of chemometric optimization enhanced sensitivity of the method with limits of detection and quantification of 1.07 and 3.57 mg/L, respectively. Comparing with previous olanzapine assay methods, which employing conventional analytical techniques, the new SIA method is inexpensive in terms of instrumentation, consumption of reagents and samples as well as effort and manpower. The SIA method is also safer for handling solutions and for the environment.     

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).     

Titrimetric and Spectrophotometric Determination of Some Phenothiazine Psychotropics in Pure Form and in Pharmaceutical Formulations with Metavanadate

 Two simple, fast, accurate and precise methods for the determination of six phenothiazines and a number of their pharmaceutical formulations are described. The titrimetric method involves the oxidation of the drugs by metavanadate in sulphuric acid medium and titration of vanadium(IV) formed, with cerium(IV) using ferroin indicator and acetone as catalyst. In spectrophotometry, vanadium(IV) formed was reacted with ferriin and the resulting ferroin measured at 510 nm. Phenothiazines in the ranges 5–100 mg and 2.5–25.0 μg mL⁻¹ can be determined by titrimetry and spectrophotometry, respectively, with detection limits of 0.96–2.05 mg and 0.0359–0.0565 μg mL⁻¹, respectively. Both methods were applied successfully to the determination of the studied drugs in pharmaceutical preparations. The reliability of the assays was established by parallel determination by the official methods of British Pharmacopoeia and the results being statistically evaluated. Received September 26, 2000. Revision March 25, 2001.     

Cerimetrie en milieu nitrique. application au dosage du fer,de l'uranium et du plutonium

A method is described for titrimetric determination of iron, uranium or plutonium in nitric acid media. The element is reduced with titanium(III) solution in presence of sulfamic acid, and titrated with cerium(IV) solution. Precautions normally taken for nitric acid media are unnecessary. The method is rapid and precise and is readily applicable to determinations of plutonium or irradiated uranium.     

Titrimetric determination of vanadium(IV) with cerium (IV)sulphate at room temperature using ferroin as indicator

A procedure has been developed for the visual titrimetric determination of vanadium(IV) with cerium(IV) sulphate, using ferroin is redox indicator. The method has been extended to the determination of iron(II) and vanadium(IV) in mixtures.     

Titrimetric and spectrophotometric methods for the determination of cerium(IV) in aqueous solution

A titrimetric and spectrophotometric methods for cerium(IV) determination have worked out. The first method relies upon the treatment of cerium(IV) solution with an excessive amount of iodide; the liberated iodine is extracted into chloroform, then reduced to iodide. The latter is iodometrically determined after 6- or 36-fold amplification. The spectropho-tometric finish is based upon the reaction of the titled ion with iron(II), in the presence of hexacyanoferrate(II), to form an intense prussian blue color suitable for the trace determination of cerium(IV) ion.     

Flow-Injection Fluorometric Determination of Novalgin in Pharmaceutical Preparations

A flow-injection configuration for the fluorometric determination of Novalgin (dipyrone) is proposed. The procedure is based on the oxidation of Novalgin by cerium(IV). The fluorescence native of cerium(III) formed in the oxidation of Novalgin is monitored. Lineal calibration graphs were obtained between 0.5 and 4 μg/ml, with a sampling rate of 40 samples/h and relative standard deviations between 0.93 and 2.8%. The applicability of the method to the determination of Novalgin in pharmaceutical preparations was demonstrated by investigating the effect of potential interferences and by analysis of commercial preparations.     

Stopped-flow--photometric and kinetic--fluorimetric methods for the determination of thyroid hormones in tablets

The catalytic effect of thyroxine and triiodothyronine on the reaction between cerium(IV) and arsenic(III) was studied by using photometric and fluorimetric measurements. The kinetic - photometric studies were based on measurement of the decrease in absorbance of cerium(IV), whereas the rate of formation of fluorescent cerium(III) was measured in the kinetic - fluorimetric studies. A modular stopped-flow system was coupled to a spectrophotometer in order to develop stopped-flow methods for the determination of thyroxine and triiodothyronine. The proposed methods were compared and applied to the determination of these hormones in pharmaceutical preparations.     

Spectrophotometric determination of cyanocobalamin (as cobalt)

A spectrophotometric method for the determination of cyanocobalamin (as cobalt) in pharmaceutical preparations has been developed. The sample is first decomposed with sulfuric acid and potassium perchlorate. The liberated cobalt is then determined using 2,2′-dipyridyl-2-pyridylhydrazone as reagent in solutions containing 20% sulfuric acid. The presence of other metal cations does not interfere with the determination of cobalt. The method has been applied to the determination of cobalt in pure cyanocobalamin and in two pharmaceutical preparations.     

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。     

New spectrophotometric and spectrofluorimetric methods for the determination of angiotensin II receptor antagonists in tablets and plasma

Spectrophotometric and spectrofluorimetric methods for the determination of five Angiotensin II type 1 receptor antagonists in tablets and plasma have been developed and optimized. The spectrophotometric method involves the addition of a measured excess of bromate-bromide in HCl medium and subsequent estimation of the residual bromine by reacting with a fixed amount of methyl orange. The spectrofluorimetric method depends on the oxidation of the drugs with cerium(IV) and subsequent monitoring of the fluorescence of the induced cerium(III) at 365 nm with excitation at 255 nm. Both of the proposed methods were successfully applied to the determination of the investigated drugs in their pure forms and pharmaceutical preparations. Besides, the spectrofluorimetric method was applied to the determination of irbesartan and telmisartan in biological fluids with good accuracy and precision.