The Determination of Methenamine and its Salts in Tablet Dosage Forms Using Ion-Pair Extraction

Abstract

This paper reports a simple, accurate, reproducible, stability-indicating procedure which may be used to quantitatively determine methenamine base, methenamine mandelate or methenamine hippurate in tablet dosage forms. The procedure initially involves the separation of methenamine from the dosage form and from formaldehyde, the decomposition product, by a cartridge ion-pair extraction process. The methenamine may then be assayed by a number of methods. In this paper the methenamine was hydrolyzed to formaldehyde and the formaldehyde determined by the Nash procedure. The method compares favorably with the USP XXI procedure for methenamine tablets. Advantages of the procedure include the ability to use a single method for the base and salt forms of the drug and the potential application to stability and quality control studies of methenamine dosage forms.     

The Use of Charge Transfer Complexation in the Spectrophotometric Determination of Some Corticosteroid Drugs Through Intermediate Oxime Formation

Abstract

Two spectrophotometric procedures for the assay of three corticosteroid drugs through oximation and subsequent charge transfer complexation with two electron acceptor substances are proposed. The optimum experimental conditions, and molar ratio of reactants were studied. The applicability of the proposed procedures to assay the tested compounds in tablets from and comparison with an official method revealed the reliability, sensitivity and accuracy of the suggested procedures.     

Spectropolarimetric Assay of R(-)-Epinephrine

Abstract

A rapid, simple and specific procedure for the simultaneous assay and determination of enantiomeric purity of pharmaceutical grade 1-epinephrine solution is described. The procedure is faster, more precise and more specific for the levoisomer than the U.S.P. XXI method. It can also be used for 1-epine-phrine inhalation solution and 1-epinephrine injection solution.     

The Simultaneous Spectrophotometric Assay of the Active Constituents of Multicomponent Analgesics Using Kalmanfiltering

Abstract

UV-spectrophotometry in combination with Kalmanfiltering is used for the assay of analgesics in tablets. Commercial products containing various combinations of acetylsalicylic acid, salicylic acid, caffeine, phenacetine and acetaminophen are analyzed. For comparison, these tablets were also analyzed by HPLC. The accuracy and precision of both methods are comparable. The described spectrophotometric assay with the aid of Kalmanfiltering represents a new, rapid and low-cost alternative to existing analytical procedures for analgesics.     

A New Sensitive Reversed‐phase High‐performance Liquid Chromatography Method for the Quantitative Determination of Metoclopramide in Canine Plasma

Abstract

A specific and sensitive high‐performance liquid chromatographic method was developed for the determination of metoclopramide in canine plasma. The procedure involves fast liquid–liquid extraction and analysis on an octadecyl silane (ODS) column. A preliminary pharmacokinetic study was performed by applying the developed method to a single oral administration of metoclopramide (MCP) to a dog. The validation method yielded good results regarding linearity, precision, accuracy, and specificity. The procedure is suitable for separation and quantification of MCP in canine plasma, enough to quantify 0.2 ng/ml when 0.5 ml of plasma is used. This assay procedure might be useful for the pharmacokinetic study of MCP in dogs.     

Solid-Phase Extraction Techniques for Assay of Diuretics in Human Urine Samples

Abstract

Solid-phase extraction techniques were evaluated for the treatment of urine samples in the analysis of diuretics before injection into an HP-Hypersyl ODS-C18 column. Six different reversed-phase extraction columns were tested, and the results obtained are compared with those obtained in a classical liquid-liquid extraction with ethyl acetate.

The solid-phase extraction procedures are the best overall choice for all the diuretics tested, due to their versatility, the minor time-consuming, and the good recovery percentages obtained. C18 and C8 packings give the highest recoveries for a majority of the diuretics studied. However, CH or PH columns, due to their greater selectivity, can be used if the elution of the matrix is not complete in the washing solution. This could be more suitable.     

Rapid Determination of Teicoplanin in Human Plasma by High Performance Liquid Chromatography

Abstract

A rapid isocratic reversed-phase HPLC method for the determination of the major component of teicoplanin in plasma is described.

By using solid phase extraction C18 and UV detection at 240 nm, this method is specific, and sufficiently sensitive.

We found a good linearity over the range: 5 – 40 mg/1 of teicoplanin plasma concentrations. The coefficients of variation did not exceed 5.4% both within-day and between-day assays.

With the small plasma sample required for the analysis (250 μl) and the good accuracy, this rapid procedure appears to be suitable for the therapeutic drug monitoring.     

Determination of Pentaerythritol Tetranitrate in Pharmaceuticals by High Performance Liquid Chromatography

Abstract

A high performance liquid chromatographic procedure for the analysis of pharmaceutical formulations containing pentaerythritol tetranitrate including the diluted bulk drug and finished products consisting of uncoated tablets and timed-release capsules and tablets was developed. The method employs a reversed-phase system with UV detection at 230 nm. Replicate analyses of 11 commercial formulations (5 diluted bulk drugs and 6 dosage forms gave precision values (CV) having a range of 0.17 to 1.80%. Recovery values obtained from these commercial preparations via fortification ranged from 98.8 to 102.0% while recoveries from 3 synthetic mixtures varied from 99.2 to 100.8%. The detector response for the analyte was observed to be linear over a 50-fold concentration range using nitroglycerin as the internal standard. The proposed HPLC method is specific, easy to perform and exhibits excellent accuracy and precision. Seven different brands of HPLC columns were evaluated for possible use with the method.     

Liquid Chromatographic Analysis of Antiepileptic Drugs: An Overview

Abstract

Extraction of antiepileptic drugs (AEDs) can be carried out by different procedures which include: (i) protein precipitation, (ii) liquid-liquid and (iii) liquid-solid extraction. The latter yields a cleaner sample and shows efficiency comparable to the other procedures; recovery ranges from 90 to 105% for most AEDs.

Types of column include: (i) conventional, (ii) microbore and (iii) high-speed. Compared with conventional and high-speed columns, microbore columns, which have a diameter of 1–2 mm, allow to achieve the highest sensibility (up to double values) and to reduce solvent consume (up to 70 %). High-speed columns, characterized by a length of 3–10 cm and by a reduced packing particle size (? 3μm), make the analysis time more rapid by at least 50%.

Reversed phase chromatography is the most versatile technique as compared to the normal phase and to the precision and accuracy. These parameters, in fact, resulted close to those of the fluorescence polarization immunoassay technique (FPIA), which was the most precise and accurate among the methods compared (79).     

Determination of Vitamin B12 in Multivitamin Tablets by High Performance Liquid Chromatography

Abstract

Two procedures for separation and determination of vitamin B₁₂ in multivitamin tablets by reversed phase high performance liquid chromatography are proposed. Sample preparation is very simple: tablets are dissolved in distilled water, centrifuged and filtered. The sample solution is directly applied in the sample loop injector and chromatograms are obtained with gradient elution using water-methanol and water-acetonitrile as solvents. The peak of vitamin B₁₂ from samples of B-complex tablets is well separated with the two procedures. For multivitamin tablets, however, only the procedure with water and methanol as solvents was good for separation and quantification of vitamin B₁₂. Both procedures were verified by the standard addition method and also compared to a previously developed method using electrothermal atomic absorption spectrometry for vitamin B₁₂ determination.     

Determination of the New Ace-Inhibitor Quinapril and Its Active Metabolite Quinaprilate in Plasma and Urine by High-Performance Liquid Chromatography and Pre-Column Labelling for Fluorescent-Detection

Abstract

A sensitive and selective method for the determination of quinapril and its active metabolite quinaprilate in human plasma and urine is described. The method is based on isolation using C18 Bond Elut cartridges, pre-column derivatization with 9-anthryldiazo-methane and purification of the reaction mixture on CBA columns followed by reversed-phase high performance liquid chromatography with fluorometric detection. Calibration curves were linear between 20 ng and 1000 ng/ml of plasma (100-2000 ng for urine) for both substances, the lower limit of detection being 5-10 ng/ml.

The present assay procedure has been applied to monotoring plasma and urine concentrations in several pharmacokinetic studies in humans.     

Liquid Chromatographic Analysis of Ciprofloxacin and Ciprofloxacin Metabolites in Body Fluids

Abstract

An isocratic HPLC assay procedure for analysis of ciprofloxacin and three metabolites was developed. The procedure requires only dilution of bile, saliva, and urine samples prior to reverse-phase chromatography on a polystyrene-divinylbenzene (PSDVB) column; analysis of serum samples requires a cleanup step on a PSDVB cartridge prior to chromatography. The dependence of chromatographic efficiency on flow rate and temperature was investigated and the accuracy, precision, selectivity, and sensitivity of the procedure were evaluated. The developed procedure was also compared to a modified version of a published ciprofloxacin procedure that requires an octadecyl-silane (ODS) column for chromatographic separation. Similar efficiency, precision, and accuracy were observed with both procedures and both were used for analysis of clinical samples. However, the procedures were used for different purposes. The PSDVB procedure, because of more favorable column selectivity, was used to assay ciprofloxacin and its metabolites in bile, urine and saliva samples. The ODS procedure, because of a simpler serum preparation step, was used t o assay ciprofloxacin in serum samples.     

Determination of Ketoconazole in Plasma and Dosage Forms by High-Performance Liquid Chromatography and a Microbiological Method

Abstract

A simple and rapid high-performance liquid chromatographic (HPLC) method for the determination of ketoconazole in plasma and in tablets was developed. the method employs benzafibrate as internal standard and is sufficiently rapid and sensitive for use in pharmacokinetic studies. Separation of the drug from plasma was achieved by extraction with acetonitrile followed by a reversed phase chromatography on a μ Bondapak column using the isocratic mobile phase of methanol-water-glacial acetic acid (67.5:32:0.5). With this eluting solvent ketoconazole and the internal standard. were well separated from the components of plasma. A linear relationship was obtained between the ratio of the area under the peak of drug to that of the internal standard versus the concentration of the drug. Data comparing the microbiological assay with the HPLC procedure, which was developed, are shown. In the microbiological assay, Candida albicans, was the test organism, using the agar diffusion technique. Both methods were applied to the assay of ketoconazole in plasma and in tablets. Excellent agreement was observed between the results from the two methods.     

Determination of Ascorbic Acid and Dehydroascorbic Acid in Blood Plasma Samples

Abstract

Following the stabilization of the plasma samples with HClO₄ and EDTA, the samples could be directly analyzed by HPLC using electrochemical detection and reversed-phase columns. The accuracy and precision of the method was evaluated using plasma samples spiked with ascorbic acid (10 μg/ml) and the results were also compared to the classical colorimetric procedure. Dehydroascorbic (5 μg/ml) was determined in plasma samples using UV detection following derivatization at room temperature for 45 minutes with o-phenylenediamine.     

Simultaneous Determination of Acetaminophen with Orphenadrine Citrate,Ibuprofen or Chlorzoxazone in Combined Dosage Forms by Zero-Crossing Derivative Spectrophotometry

Abstract

A derivative spectrophotmetric procedure for the simultaneous determination of acetaminophen-orphenadrine citrate, acetaminophen-ibuprofen and acetaminophen-chlorzoxazone, binary mixtures is described. The procedure minimises the mutual interference between these drugs in mixtures and allows the determination of these compounds without a previous extraction step. The precision of the method, expressed as the relative standard deviation, is better than 4%. The method has been successfully applied to laboratory mixtures and commercial tablets containing these drugs.     

Determination of Ketotifen Fumarate in Raw Material and Pharmaceutical Products Using Ion‐pair Formation

Abstract

A simple and sensitive extractive spectrophotometric method has been described for the determination of Ketotifen. The developed method is based on the formation of a colored ion‐pair complex (1∶1 drug/dye) of Ketotifen and bromocresol green in buffer pH 3 and extraction in chloroform. The extracted complex shows absorbance maxima at 423 nm. Beer's law is obeyed in the concentration range of 5.15–61.91 µg/ml. The proposed method has been applied successfully for the determination of drug in commercial tablets and syrup dosage form. No significant interference was observed from the excipients commonly used as pharmaceutical aids with the assay procedure.     

Simultaneous High Performance Liquid Chromatographic Determination of Theophylline and Ethylenediamine in Aminophylline Dosage Forms as Their Dansyl Derivatives

Abstract

A simple HPLC method has been developed for the assay of the components of aminophylline (theophylline: ethylenediamine 2:1) in solid and liquid dosage forms. Following the extraction of tablets into or the dilution of a liquid dosage form with water, the aqueous extract was reacted with dansyl chloride in an alkaline medium. The mixture of the dansyl derivatives of theophylline and ethylediamine was analyzed on an reversed phase μBondapak Cia column, using a methanol-water-acetic acid-triethylamine (60–65: 33–38: 1. 5:0. 5) mobile phase delivered at the rate of 1.5 mL/min, and a detection wavelength of 254 nm. In addition to exhibiting excellent accuracy and precision, the method yielded detector responses that were linearly related to concentrations of theophylline and ethylenediamine in aminophylline of up to 7 mg of theophylline, and of up to 10 mg     

High-Performance Liquid Chromatographic Determination of Atenolol in Tablets

Abstract

A reversed phase high-performance liquid chromatographic method was developed for the determination of atenolol in four oral 100 mg atenolol preparations.

An aliquot of the sample is dissolved in a mobile phase consisting of 0.0612 M potassium hydrogen phosphate - isopropanol-tetrahydrofuran (84:10:6) v/v). The pH was adjusted to 6.7 with phosphate buffer. Nicotinamide was used as internal standard and chromatographed on a Pinkerton column ISRP (GFF-S5–80) 5 μm, 150 × 4.6 mm i.d. The applied column is convenient for the assay at least 90 samples of atenolol without degrading column performance. The detection was performed at 272 nm. The retention time for atenolol was 5.07 min.

The proposed HPLC method was found to be suitable for the rapid and precise routine analysis of atenolol in tablets.     

Determination of Formaldehyde in the Polymerized Ragweed Antigen by HPLC

Abstract

Formaldehyde is used in the polymerization of ragweed antigen for the desensitization treatment of hay fever. Because the polymerized ragweed antigen is used as a vaccine which stimulates the production of the desired immunological effects upon injecting into the body, trace formaldehyde in the injected material is a health concern. Two procedures for the determination of formaldehyde were developed. In the direct procedure, formaldehyde in the sample was reacted with 2,4-dinitrophenylhydrazine (2,4-DNP) in solution to yield a strongly UV absorbing derivative. In an alternate approach, formaledhyde in the sample in a sealed vial was allowed to diffuse in the gaseous form into a reaction chamber consisted of a culture tube insert in which formaldehyde was derivatized with 2,4-DNP reagent. Following extraction into methylene chloride, the derivative was injected into the liquid chromatograph, separated on a reversed phase column and detected at UV 254 nm.     

High Performance Liquid Chromatographic Assay of phenylbutazone in Pharmaceutical Dosage Forms

Abstract

A simple, rapid and reliable high performance liquid chromatographic procedure for the quantitation of phenylbutazone in pharmaceutical dosage forms was developed, and compared with the U. S. P. XXI method and a spectrophotometric assay developed in this laboratory. A comparison of the three methods indicated that the HPLC method is the most rapid, simple and reproducible. The recoveries based on six placebo samples were 100.2, 99.2, and 99.4% by HPLC, UV and the U. S. P. method, respectively, and their respective CVs were 0.39, 0.73, and 1.5%. Replicate regression analyses of three standard plots in the concentration range of 0.02-0.12 mg/ml obtained using the HPLC assay on three different days yielded a correlation coefficient <0.999 and the coefficient of variation for the three slopes was 1.05%. It is suggested that the proposed HPLC method should be used for routine quality control and dosage form assay of phenylbutazone.