Determination of Some Pharmaceutically – Important Aminoquinoline Antimalarials,via Charge – Transfer Complexes

Abstract

A simple and rapid spectrophotometric method for the assay of amodiaquine hydrochloride, chloroquine phosphate and primaquine phosphate is described. The method is based on the interaction of the drug with 7, 7, 8, 8-tetracyanoquinodimethane (TCNQ) as a π-electron acceptor, forming a highly coloured stable radical anion. The molecular ratios of the reactants in the complexes as well as the experimental conditions leading to maximum charge-transfer bands have been studied. Beer's Law is obeyed over aminoquinoline antimalarials concentration range of 0.4–4.0 ug.ml^?1. The proposed procedure has been applied successfully to the analysis of antimalarials in their dosage forms and the results are in agreement with those of official methods.     

Quantitation of Baclofen in Tablets Using High-Performance Liquid Chromatography

Abstract

A reverse phase high-performance liquid chromatography method has been developed to quantify baclofen in tablets. The method is accurate and precise with a percent relative standard deviation of 0.52 based on 5 readings. The recovery from the synthetic mixtures was quantitative. The results were in excellent agreement with the USP-NF colorimetric method. The method can be used to test the content uniformity of the tablets. Samples which were treated with either sulfuric acid or sodium hydroxide and boiled for 10 minutes did not show new peaks in the chromatogram. Baclofen appears to be a very stable compound.     

Quantitation of Terbutaline Sulfate in Pharmaceutical Dosage Forms Using High Performance Liquid Chromatography

Abstract

A stability-indicating reverse phase high-performance liquid chromatography method has been developed to quantify terbutaline sulfate in pharmaceutical dosage forms. The method is accurate and precise with percent relative standard deviations based on 6 readings of 0.6 with an internal standard (salicylic acid) and 0.8 without an internal standard. The results are in excellent agreement with the USP-NF method. A decomposed sample gave 49.4% results with the developed method versus 71.3% with the USP-NF method.     

Colorimetric Determination of Isoetharine Hydrochloride in Inhalation Solutions

Abstract

A simple colorimetric assay method has been developed to quantify isoetharine hydrochloride in inhalation solutions. The method is based on a very simple reaction with potassium ferricyanide in a 0.05 M phosphate buffer solution. The color so developed can be measured at 500 nm. Beer's law was followed. The results were precise and accurate, with percent relative standard deviation of 0.6 based on 5 readings. The results using the developed method were in excellent agreement with the results obtained using the USP-NF method which is based on HPLC. Iodine solution was used to prevent the interference from the antioxidant (acetone sodium bisulfite). There was no interference from the other excipients present and from the two structurally related compounds, metaproterenol and terbutaline     

Development of a synthetic route towards N4,N9-disubstituted 4,9-diaminoacridines: On the way to multi-stage antimalarials

A multi-step synthetic route towards N⁴,N⁹-disubstituted 4,9-diaminoacridines that, to the best of our knowledge, has no precedence in the literature, has been developed. The target structures are likely to reveal interesting biological activities in the near future, not only due to their mepacrine-like core, but also because they embed simultaneously the pharmacophores of chloroquine and primaquine, antimalarial drugs that act at different stages of malaria infection.     

Determination of the Antimalarial Primaquine in Whole Blood and Urine by Normal-Phase High-Performance Liquid Chromatography

Abstract

A method has been developed to estimate primaquine in whole blood and urine by sensitive and selective high-performance liquid chromatography. Using the linear chain analogue of primaquine as the internal standard, a single-step extraction, normal-phase silica column with a basic mobile phase, levels down to 1 ng/ml of primaquine could be measured with good precision. Other anti-malarials like amodiaquine and pyrimethamine did not interfere in the assay. The major carboxylic acid metabolite of primaquine did not elute under the normal-phase chromatographic conditions. The method is suitable for use in clinical pharmacokinetic studies with primaquine.     

Spectrophotometric Microdetermination of Some Pharmaceutically Impor tant Aminoquinoline Antimalarials, as Ion-Pair Complexes

 A simple, rapid, accurate and sensitive spectrophotometric method for the microdetermination of some pharmaceutically important aminoquinoline antimalarials, namely amodiaquine dihydrochloride (I), chloroquine phosphate (II) and primaquine phosphate (III) is described. The method is based on the interaction of these drugs with calmagite indicator to give highly coloured ion-pair complexes which exhibit maximum absorption at 663, 665 and 666 nm, respectively, Beer’s law is obeyed in the concentration ranges 1.0–25.0, 1.0–28.0 and 1.0–33.0 μg/ml for the drugs I, II and III, respectively. For more accurate analysis, the Ringbom optimum concentration ranges are 2.5–22.5, 2.0–26.0 and 3.0–30.0 μg/ml, respectively. The apparent molar absorptivities were calculated. Statistical treatment of the experimental results indicates that the method is sufficiently accurate and precise. The accuracy of the method is indicated by the recovery (99.8±1.4%) and the precision by the relative standard deviation (>1.5%). The proposed method has been applied to the determination of these drugs in certain formulations, with results that compared favourably with those obtained by the official methods. Received November 2, 1998. Revision February 29, 2000.     

Analytical Applications of Ion-Exchange Materials. V. Chromatographic Separation of Drugs on Ferric Phosphate Papers

Abstract

Chromatography of 14 drugs is performed on papers impregnated with ferric phosphate. Nine solvent systems are used based on aqueous phosphate buffers and mixed organic solvents. The Rf values on plain papers and impregnated are compared. Some important binary separations are practically achieved.     

Spectrophotometric Determination of Risedronate and Etidronate in Pharmaceutical Formulations via the Molybdovanadate Method

Abstract

An accurate and sensitive spectrophotometric method was developed for the determination of risedronate and etidronate in pharmaceuticals. The method was based on oxidation of the studied drugs with potassium persulfate and reaction of the generated orthophosphate ions with molybdovanadate reagent. The produced yellow phosphovanadomolybdate complex was measured at 313 nm. The method was rectilinear in the ranges 0.5–10 and 0.5–8 µg/mL with detection limits of 0.087 and 0.122 µg/mL for risedronate and etidronate, respectively. The method was applied for the determination of the studied drugs in their tablets, and the results agreed with those obtained by the comparison methods.     

Determination of Mefenamic Acid and Paracetamol by First Derivative Spectrophotometry

Abstract

A direct and simple first derivative spectrophotometric method has been developed for the determination of mefenamic acid and paracetamol in pharmaceutical formulations. A methanolic hydrochloric acid solution was used as solvent for extracting the drugs from the formulations and subsequently the samples were evaluated directly by derivative spectrophotometry. Simultaneous determination of both drugs can be carried out using the zero-crossing and the graphical methods. The methods do not require simultaneous equations to be solved. The calibration graphs were linear in the ranges from 1.8 × 10^?6 to 1.6 × 10^?4 M of mefenamic acid and from 4.1×10^?6 to 1.4 × 10^?4 M of paracetamol. The ingredients commonly found in commercial pharmaceutical formulations do not interfere. The proposed method was applied to the determination of these drugs in tablets.     

Spectrophotometric determination of some pharmaceutically-important aminoquinoline antimalarials

A simple and rapid spectrophotometric method for the assay of amodiaquine hydrochloride, chloroquine phosphate and primequine phosphate is described. The method is based on the interaction of the drug with tetracyanoethylene to give a stable charge transfer complex. The spectra of the complex show maxima at 413, 415 and 415nm, respectively, with high apparent molar absorptivities. Beer's law is obeyed in the concentration ranges 2–12, 1–8 and 2–12 g ml^–1 of the three drugs studied. The proposed method is applied to the determination of these drugs in certain formulations and the results are favourably comparable to the official methods.     

Extraction - Spectrophotometric Determination of Phosphate Using N-Phenylbenzohydroxamic Acid

Abstract

A simple solvent extraction and spectrophotometric method for the determination of micro amount of phosphate (PO₄) is described. Phosphate is selectively separated from associated elements by reacting it with calcium and extracting excess calcium with N-phenylbenzohydroxamic acid (PBHA) at pH 11.3. The excess calcium was determined in ultra-violet and visible region and hence the phosphate content was calculated. The Beer's law is obeyed in the range 0.5 ? 10.0 ppm at 340 nm and 0.25 - 8.0 ppm at 560 nm of phosphate for a fixed amount of calcium (20.0 ppm). These results are also compared with those obtained by atomic absorption spectrophotometry. The method has been applied for the determination of phosphate in pharmaceutical and other samples.     

Quantitation of Glipizide and Glyburide in Tablets Using High Performance Liquid Chromatography

Abstract

Reverse phase high-performance liquid chromatography methods for the quantitation of glipizide and glyburide in tablets have been developed. The methods are accurate and precise with a percent relative standard deviations based on 6 injections of 0.8 and 0.3% for glipizide and glyburide, respectively. The developed methods can be used to test the content uniformity of the tablets. The extraction procedure for the active ingredients from the tablets is very simple. There is no interference from the excipients and the acid hydrolyzed samples showed new peak in the chromatograms.     

Resolution of Overlapped Capillary Electrophoresis Peaks by Using Heuristic Evolving Latent Projections to Quantify Chloroquine Phosphate and Promethazine Hydrochloride

Chloroquine phosphate and promethazine hydrochloride are two main components in compound reserpine tablets. It is difficult to separate the two compounds with capillary electrophoresis (CE). Heuristic evolving latent projections (HELP) is a chemometric algorithm which is suitable for resolving overlapped peaks from CE and HPLC. In this paper, HELP was applied to resolving the completely overlapped peaks of chloroquine phosphate and promethazine hydrochloride from CE. Mathematical separation and satisfactory quantification results can be achieved easily without too much time involved in the procedure.     

Determination of Phosphate by Cathodic Stripping Voltammetry at a Glassy Carbon Electrode

Abstract

The oxidation of Fe(II) in the presence of phosphate results in a film of a sparingly soluble Fe(III) phosphate salt on a glassy carbon electrode. The reaction is used as the preconcentration step in a cathodic stripping method for phosphate. The recommended procedure yields working curves which are linear over single orders-of-magnitude down to 0.1 ppm, With a 40-minute preconcentration time, 40 ppb phosphate can be detected. The method is free of interference by chloride and sulfate.     

Phosphate Bonded Refractories and Insulating Materials

Abstract

The fundamental studies in phosphate bonding carried out by Kingery (1) in the USA in early fifties gave rise to worldwide investigations and practical application of a new type of refractories and insulating materials. The use of phosphate binders made it possible to develop a unique class of refractories and insulating materials with principally novel technical properties. Theoretical investigations and power-saving nonwaste technology of their production has been developed in Orgtehstrom from the early seventies. The result of these activities was industrial production of phosphate bonded refractories and insulating materials on a commercial basis; the technology was introduced in all ceramics and glass works of construction material industry of the Latvian SSR.     

Detection and determination of antimalarial drugs and their metabolites in body fluids

This review of methods for determining antimalarial drugs in biological fluids has focused on the various analytical techniques for the assay of chloroquine, quinine, amodiaquine, mefloquine, proguanil, pyrimethamine, sulphadoxine, primaquine and some of their metabolites. The methods for determining antimalarials and their metabolites in biological samples have changed rapidly during the last eight to ten years with the increased use of chromatographic techniques. Chloroquine is still the most used antimalarial drug, and various methods of different complexity exist for the determination of chloroquine and its metabolites in biological fluids. The pharmacokinetics of chloroquine and other antimalarials have been updated using these new methods. The various analytical techniques have been discussed, from simple colorimetric methods of intermediate selectivity and sensitivity to highly sophisticated, selective and sensitive chromatographic methods applied in a modern analytical laboratory. Knowledge concerning the method for a particular study is determined by the type of application and the facilities, equipment and personnel available. Often is it useful to apply various methods when conducting a clinical study in malaria-endemic areas. Field-adapted methods for the analysis of urine samples can be applied at the study site for screening, and corresponding blood samples can be preserved for subsequent analysis in the laboratory. Selecting samples for laboratory analysis is based on clinical, parasitological and field-assay data. The wide array of methods available for chloroquine permit carefully tailored approaches to acquire the necessary analytical information in clinical field studies concerning the use of this drug. The development of additional field-adapted and field-interfaced methods for other commonly used antimalarials will provide similar flexibility in field studies of these drugs.     

Development of Calcium Phosphate Glass-Ceramics for Surgical and Dental Use

Abstract

Two types of glass-ceramics have been developed in the system of calcium phosphate without silica. The preparation conditions, crystallization processes, and some of physical properties are briefly reported. These glass-ceramics have high potential use for bone substitutes and dental materials such as dental crown, root and tooth.     

Carbon-13 nuclear magnetic resonance spectra of potent antimalarials: Primaquine and chloroquine

C¹³ Nmr chemical shits of primaquine and chloroquine are reported. The signals are assigned on the basis of substituent effects on benzene shifts, intensities, multiplicities in SFORI) and the comparison with structurally related compounds.     

A Novel Method for the Synthesis of Acetyl Phosphate

A facile method for the synthesis of acetyl phosphate by a reaction of 2-hydroxypropylphosphate with acetic acid is described.