Spectrophotometric determination of metronidazole in pharmaceutical pure and dosage forms using p-benzoquinone

A simple and accurate spectrophotometric method for the determination of metronidazole in pure and pharmaceutical dosage forms has been developed. The proposed method is based on the reduction of the nitro group to amino group of the drug. This can be achieved by heating a mixture of an alcoholic solution of metronidazole, zinc powder and dilute hydrochloric acid in a water bath at 90 ± 5 °C for 15 min. The cold and clear filtrate reacts with p-benzoquinone to develop a purple color, which absorbs maximally at 526 nm. The calibration graph is linear over the concentration range of 15–190 μg ml^?1 with a molar absorptivity of 1.09 × 10³ l mol^?1 cm^?1. The proposed method is applied to commercially available pharmaceutical dosage forms and the results are statistically compared with those obtained by the reference method.     

Photochemistry of azidostyrylquinolines: 1. Quantum-chemical study of the structure in the ground and the lower excited singlet states

The structures of isomeric 2-and 4-azidostyrylquinolines and their protonated forms in the ground (S ₀) and the lowest excited singlet (S ₁) states were calculated by the PM3 semiempirical method and the density functional theory (DFT) using the B3LYP/6-31G^* basis set. It was shown that the σ _NN ^* molecular orbital, which is localized on the azide group and is antibonding for the N-N₂ bond, is populated in the S₁ state of these azides in both neutral and protonated forms. Based on this result, it was assumed that the test azides would be photoactive in both forms, i.e., would have a photodissociation quantum yield of φ > 0.1. The calculation of absorption spectra by the TD B3LYP/6-31G^* method showed that the long-wavelength absorption bands of the protonated forms are shifted to visible spectral region, thus suggesting that azidostyrylquinolines in the protonated form will be sensitive to visible light.     

Spectrophotometric Determination of Piroxicam via Chelation with Fe(III) in Commercial Dosage Forms

The objective of this work is to develop and validate spectrophotometric method for the determination of piroxicam in commercial dosage forms. The method is based on the chelation of the drug with Fe(III) to form pink coloured metal chelate at room temperature which absorbs maximally at 504 nm. Beer's law is obeyed over the concentration range of 8–160 μg mL^?1 (A = 1.07 × 10^?3 + 7.75 × 10^?3 C). Under the optimized experimental conditions, proposed method is validated as per the International Conference on Harmonisation guidelines. The limits of detection and quantitation for the proposed method are 0.775 and 2.348 μg mL^?1, respectively. The proposed method has been successfully applied to the determination of piroxicam in commercial dosage forms. The results are compared with the reference El‐Ries et al. spectrophotometric method.     

The Characterization of a New Reagent N-allyl-N'-(Sodium P-Aminobenzenesulfonate Thiourea,and its Application to Determination of Pd(II)

ABSTRACT

The study of a new water-soluble reagent, N-allyl-N ' -(sodium p-aminobenzenesulfonate)thiourea (ASAT)'s preparation and its characteristics are described. It was found that in pH 4.0-5.5 NaAc-HAc buffer solution, ASAT forms a stable yellow soluble complex with Pd²⁺. The maximum absorption is at 296 nm, ?=1.33×10⁵1 mol^?1 cm^?1. Higher sensitivity and selectivity are advantages of this method. The new method is simple and convenient and can provide satisfactory results on samples of anode mud and ore.     

Spectrophotometric Determination of Lisinopril in Pure and Pharmaceutical Formulations

An accurate, simple, fast, and cheap spectrophotometric method has been developed for the determination of lisinopril in pharmaceutical pure and dosage forms. The method is based on the reaction of ninhydrin with primary amine present in the lisinopril in the presence of DMF. This reaction produces a greenish blue colored product which absorbs maximally at 600 nm. Beer's law was obeyed in the range of 10–150 μg/mL with molar absorptivity of 4.083 × 10³ L mole^?1 cm^?1. The effects of variables such as temperature, heating time, concentration of color producing reagent, and stability of color were investigated to optimize the procedure. The results are validated statistically. The proposed method was applied to commercially available tablets, and the results were statistically compared with the official potentiometric method.     

Tracer experiments for the determination of chemical forms of radioiodine in water samples

Two simple methods, (1) isotope exchange method and (2) anion exchanger column method, are developed for the determination of chemical forms of radioiodine (iodide and iodate) in water samples. Using these methods, transformations of chemical forms of iodine in various water samples were studied. It was observed that iodate in rain water (unfiltered) and milk tended to change iodide form, whereas iodide was converted to iodate form in seawater and tap water. After the Chernobyl accident both chemical forms of¹³¹I (iodide and iodate) were found in rain water samples collected in Japan.     

Speciation and estimation of radioiodine in reactor coolant water

The species of radioiodine in the primary coolant water of the heavy water moderated, heavy water cooled 100 MW research reactor have been identified. It was observed that IO ₃ ^? was the major species in the reactor coolant during reactor operation and I^? was the major species during shutdown. Organic and elemental forms amount only to less than 2% of total radioiodine. A simple method was developed for the estimation of gross iodine activity in reactor coolant water. The method involves the separation of all inorganic forms of iodine into a photographic film consisting of a thin layer of silver halide. The iodine in the film was estimated by gross counting of the film in a Geiger-Müller counter. Gross iodine activity in the reactor coolant samples estimated by the present method were in agreement with that obtained by direct γ-spectrometry with a Ge detector. It is concluded that the method can be used for the routine estimation of radioiodine in reactor coolant water.¹³³I/¹³¹I and¹³⁵I/¹³¹I ratios in the film were estimated and found to be useful in identifying split rod conditions in the reactor.     

Speciation of aluminium fluoride complexes and Al in soils from the vicinity of an aluminium smelter plant by hyphenated High Performance Ion Chromatography Flame Atomic Absorption Spectrometry technique

The paper presents a new tool for the determination of inorganic speciation forms of aluminium: AlF_n^{(3 − n)+}, and Al³⁺ by means of the HPIC-FAAS. The proposed method has been successfully used for speciation analysis (qualitative and quantitative) of inorganic aluminium forms AlF_n^{(3 − n)+} in soil samples. In order to isolate the most environmentally available fraction, 5 g of the sample was collected and extracted in deionised water (water soluble fraction) for 1 h using a magnetic stirrer. The determinations in a hyphenated technique system were performed for a number of prepared water extracts. Concentration determinations of particular aluminium forms were performed based on model studies and real samples. The separation of Al species with nominal charge of + 1, + 2, and + 3 required a run time of less than 4 min during a single analysis. Based on the analysis of water extracts of soil, it was obtained that aluminium forms elute in the following order: 1PA (first signal) — AlF₂⁺ and/or AlF₄⁻; 2PA (second signal) — AlF²⁺ and/or AlF₃⁰; 3PA (third signal) — Al³⁺. In order to confirm the occurrence of these forms a simulation using the Mineql program was conducted. The details of speciation analysis of aluminium fluoride forms by means of an HPIC-FAAS instrument equipped are presented. Interpretation of the speciation analysis of the water soluble fraction of soil samples is proposed, based on the separation during chromatographic run and calculated data by Mineql.     

Spectrophotometric method for determination of atrazine and its application to commercial formulations and real samples

A simple sensitive spectrophotometric method has been developed for the determination of atrazine in herbicide formulations and real samples. The method was based on the reaction of atrazine with pyridine to form a quaternary halide which in the presence of alkali forms a carbinol base. The heterocyclic ring of the carbinol base breaks and forms the glutaconic dialdehyde. The glutaconic dialdehyde group was coupled with sulfanilic acid to form a yellow coloured product having λ _max 450 nm or coupled with aniline to form a orange red coloured product having λ _max 480 nm. The Beer's law was obeyed over the range from 0.1 to 25 µg mL^?1 and molar absorptivity 1.5 × 10⁴ L mol^?1 cm^?1 for sulfanilic acid, and from 0.08 to 12 µg mL^?1 and molar absorptivity 1.3 × 10⁴ L mol^?1 cm^?1 for aniline were observed. The reaction conditions and other analytical parameters were optimised. The proposed method has been successfully applied for the analysis of commercial formulations and real samples.     

Development of a new analytical method for online simultaneous qualitative determination of aluminium (free aluminium ion, aluminium-fluoride complexes) by HPLC-FAAS

The paper presents a novel method for simultaneous online examination of inorganic forms of aluminium: AlF₂⁺, AlF^2+, and Al³⁺ by means of the high performance liquid chromatography hyphenated with a detection by the atomic absorption spectrometry with flame atomization (HPLC-FAAS) without post-column reaction. The application of optimization procedure conditions of chromatographic separation of inorganic forms of aluminium was achieved by the analytical column IonPac CS5A (Dionex) with guard column IonPac CG5A (Dionex) and an aqueous ammonium chloride mobile phase, at pH about 3 with gradient elution. The separation of Al forms with nominal charge of 1+, 2+, 3+ required a run time of less than 8 min during a single analysis. The proposed method has been successfully used for the examination of aluminium forms formation AlF_n⁽³⁻ⁿ⁾⁺ in environmental samples.     

NMR Study of Reactions between Pd,Ru, and Rh Nitrite Complexes with Sulfamic Acid

Reactions of nitrite complexes of Pd, Ru, and Rh with sulfamic acid were studied by the ^{14, 15}N, and ¹⁷O NMR method. Chemical shifts were assigned, and the predominant forms of the complexes were established. The reaction products at room temperature are cis-nitroaqua complexes. Coordination of the sulfamate ion upon storage for a long time or on heating was detected.     

Ion-Pair RP-LC of Tegaserod Maleate and its Impurities in Pharmaceutical Formulations and in Dissolution Studies

A simple ion-pair reversed-phase high-performance liquid chromatographic (RP-HPLC) method has been developed for determination of tegaserod maleate and related impurities in tablet dosage forms. The mobile phase was 60:40 (v/v) acetonitrile-25 mmol L^?1 sodium dodecyl sulfate, adjusted to pH 2.6 with glacial acetic acid. A C18 column was used as stationary phase and UV detection was at 314 nm. The method was optimized and validated. Response was linearly dependent on concentration between 0.1 and 100 µg mL^?1 with a limit of quantification (LOQ) of 0.1 µg mL^?1 for tegaserod maleate (S/N = 10). Under optimum conditions, tegaserod maleate was successfully separated from related substances, including 5-methoxyindole-3-carboxaldehyde remaining after synthesis and other impurities possibly resulting from oxidization and decomposition. The excipients did not interfere with assay of tegaserod maleate in tablet dosage forms. It is suggested that the proposed method can be used for routine quality control and dosage-form assay of tegaserod maleate.     

Electrochemical Reduction of Metronidazole and Its Determination in Pharmaceutical Dosage Forms by D.C. Polarography

Abstract

A simple d.c. polarographic method has been developed for the determination of metronidazole in dosages forms. In Robinson - Britton buffer (pH 4.38) and in presence of 1.60 × 10^?3 % Triton X-100, the drug produced a well defined 4-electron polarographic wave followed by another wave of about half the height of the first wave. The current is proportional to the concentration and permits the drug to be determined by d.c. polarography in the concentration range 5.0 × 10^?5 -7.0 × 10^?4 M. Results obtained by the proposed method are in excellent agreement with that provided by the USP-XX method. A rapid, sensitive and accurate polarographic method for the determination of metronidazole in the tablets which are produced locally is proposed.     

Determination of intracellular glutathione and cysteine using HPLC with a monolithic column after derivatization with monobromobimane

An optimized high‐performance liquid chromatography (HPLC) method is used to show that, as myoblasts differentiate into multinucleated muscle fibers, there is a shift to a more oxidized cell redox state. The HPLC method incorporated derivatization with monobromobimane for the determination of the reduced (GSH) and oxidized (GSSG) forms of glutathione and the reduced (Cys) and oxidized (CysSS) forms of cysteine. The derivatization was optimized to improve the sensitivity of the approach; the limits of detection for glutathione and cysteine were 3 × 10^?8 and 5 × 10^?8 M , respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

Quantitation of Diltiazem Hydrochloride in Commercial Dosage Forms by Visible Spectrophotometry

A selective and sensitive visible spectrophotometric method has been described for the quantitation of diltiazem hydrochloride in commercial dosage forms. The method is based on the reaction of the tertiary amino group of the drug with sodium hypochlorite to form the chloro drug derivative, followed by the destruction of the excess hypochlorite by sodium nitrite and the subsequent development of blue color takes place by the reaction of chloro derivative of drug with starch and potassium iodide in sodium bicarbonate medium. The maximum absorbance of the resulting blue solution is read at 540 nm. Under the optimized experimental conditions, Beer's law is obeyed in the concentration range of 2.5–25.0 μg mL^?1 with a linear regression equation of A = 9.85 × 10^?4 + 4.90 × 10^?2 C and coefficient of correlation, r = 0.9999. The molar absorptivity is found to be 2.26 × 10⁴L mol^?1 cm^?1. The limits of detection and quantitation of the proposed method are 0.12 and 0.37 μg mL^?1, respectively. The proposed method has been successfully applied for the quantitation of diltiazem hydrochloride in commercial dosage forms. The results of the proposed method compared with those of Abdellatef's spectrophotometric method presented good mean recovery with acceptable true bias of all pharmaceutical samples within ± 2.0%.     

Determination of99Tc in reactor loop decontamination liquid waste using extraction chromatography

A new analytical method has been developed to determine⁹⁹Tc in samples of aqueous radioactive waste containing high levels of⁶⁰Co (10³–10⁶ Bq/l) in mixed forms (simple cationic⁶⁰Co²⁺ and coordinated complex forms). The method consists of selective extraction of the⁹⁹Tc with a combination of cation exchange and solid-phase extraction resins under strong acid conditions. Quantification of the isolated⁹⁹Tc is accomplished using liquid scintillation counting. The method provides high recoveries (>98%), is simpler than classical solvent extraction methods, eliminates the use of chlorinated organic solvents and the time of analysis is reduced by a factor of 2 when compared to solvent extraction methods.     

Strontium-90 determination in biological and environmental samples by direct milking of its daughter product, yttrium-90

A method is presented for the determination of ⁹⁰Sr in environmental samples by direct milking of ⁹⁰Y. Pyridine-2,6-dicarboxylic acid forms an anionic complex with yttrium which is retained on an anionic resin. Most of the matrix elements are washed out of the column as neutral or uncomplexed species and yttrium is eluted by increasing the ionic force of the eluent solution. This method gives yttrium recoveries between 65% to 85% for soil, grass, milk and bone samples with very high radiochemical purity (⁹⁰Y average half-life of 66±4 hours) and a detection limit of 0.3 Bq/kg of soil. The method supports a calcium content up to 3 g per sample without any decrease in yttrium yield, allowing the measurement of milk, milk-teeth and bone samples with no concentration step in one day.     

Electronic absorption spectra for free hydrazyl radicals,their ionic forms and initial hydrazines

The results of the calculations of π–π^* transition energies of some free hydrazyl radicals, their ionic forms and initial hydrazines by the SCF –MO –LCAO method with restricted configuration interaction are presented. The comparison of the data obtained with the electronic spectra experimentally found, revealed that the absorption of radical solutions in the visible area was due to the electronic structure of radical molecules, the contribution of ionic forms to the absorption being negligible.     

Direct and Derivative Spectrophotometric Determination of Zinc with 2,4-Dihydroxybenzaldehyde Isonicotinoyl Hydrazone in Potable Water and Pharmaceutical Samples

A simple and sensitive spectrophotometric method is developed for the determination of zinc in aqueous solutions. The metal ion forms a greenish-yellow colored complex with 2,4-dihydroxybenzaldehyde isonicotinoyl hydrazone (2,4-DHBINH) in the pH range of 4–10. The complex shows maximum absorbance at 390 nm and in the pH range of 6–8. Beer's law is obeyed in the range 0.10–1.50 μg/mL of Zn(II). The molar absorptivity and Sandell's sensitivity are 3.55 × 10⁴ mol⁻¹ cm⁻¹ and 0.0016 μg/cm², respectively. The composition of the complex is 1 : 1. The effect of interfering ions has been studied, and the method was applied to the determination of zinc(II) in potable water and pharmaceutical samples. A fast derivative spectrophotometry method is also proposed for the determination of zinc in the range 0.06–1.60 μg/mL, which is more sensitive than the zero order method. __________ Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 9, 2005, pp. 933–937. Original Russian Text Copyright ? 2005 by Sivaramaiah, Raveendra Reddy. The text was submitted by the authors in English.     

Development and Validation of a Stability-Indicating HPLC Method for Determination of Ciprofloxacin Hydrochloride and its Related Compounds in Film-Coated Tablets

The objective of the current study was the development and subsequent validation of a simple, sensitive, precise and stability-indicating reversed-phase HPLC method for the determination of ciprofloxacin HCl in pharmaceutical dosage forms in the presence of its potential impurities. The chromatographic separation of ciprofloxacin HCl and its related compounds was achieved on an Inertsil ODS3 column using UV detection. The optimized mobile phase consisted of phosphoric acid solution: acetonitril. The proposed method provided linear responses within the concentration range 250–750 μg mL⁻¹ for ciprofloxacin HCl and 0.5–1.5 μg mL⁻¹ for its related compounds. LOD and LOQ values for the active substance were 5.159 and 15.632 μg mL⁻¹, respectively. Correlation coefficients (r) of the regression equations for the impurities were greater than 0.99 in all cases. The precision of the method was demonstrated using intra- and inter-day assay RSD% values which were less than 1% in all instances. No interference from any components of pharmaceutical dosage forms or degradation products was observed.