Spectrophotometric determination of oxytetracycline in pharmaceutical preparations using sodium molybdate as analytical reagent

A spectrophotometric method is proposed for the determination of oxytetracycline in pharmaceutical preparations. The method is based on the measurement of the absorbance of the molybdate—oxytetracycline complex at 404 nm (pH 5.50; μ = 0.1 M; 20°C). The composition of the complex (1:1) was determined by the application of the spectrophotometric methods of Job and Bent—French (pH 5.50; λ = 390 nm; μ = 0.1 M). The relative stability constant (K′ = 10^4.6) of the complex was obtained by the methods of Sommer and Nash (pH 5.50; λ = 390 nm; μ = 0.1 M; 20°C). The molar absorptivity of the complex was 9.5 × 10³ l mol⁻¹ cm⁻¹. Beer's law was obeyed over the concentration range 2.48–34.78 μg ml⁻¹. The relative standard deviation RSD (n = 10) was 0.27–0.39%. The method proposed can be applied to the assay of oxytetracycline in capsules. The detection limit of oxytetracycline is 2.5 μg ml⁻¹.     

Fluorimetric assay of rufloxacin in serum and in pharmaceutical formulations

A simple and rapid fluorimetric method for the determination of 9-fluoro-10-[N-(4′-methyl)piperazinyl]-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-d,e][1–4]benzothyazin-6-carboxylic acid hydrochloride (MF 934), in serum and in pharmaceutical formulations, has been developed based on its strong fluorescence, in 0.1 N H₂SO₄, at 526 nm (excitation wavelength at 340 nm). The procedure which involves the direct dilution of the sample requires only a few minutes and the sample volume is only 20–100 μl of serum, depending on the drug concentration. Tedious sample preparation procedures such as extraction, deproteinization, or centrifugation are not necessary. The minimum concentration that can be detected is 0.3 ng ml⁻¹, the standard curve in 0.1 N H₂SO₄ was found to be linear from 0.005 to 1.5 μg ml⁻¹ and from 0.01 to 0.07 g in plasma after dilution with 0.1 N H₂SO₄.     

Spectrophotometric method for the determination of verapamil hydrochloride in pharmaceutical formulations using N-bromosuccinimide as oxidant

A rapid, simple and sensitive validated visible spectrophotometric method has been described for the assay of verapamil hydrochloride either in pure form or in pharmaceutical formulations. The method involves the oxidation of the verapamil hydrochloride with N-bromosuccinimide in perchloric acid medium at room temperature, leading to the formation of a yellow colored product, which absorbs maximally at 415 nm. Under the optimized experimental conditions, the color is stable up to 45 min and Beer's law is obeyed in the concentration range of 10.0-200.0 microg ml(-1) with molar absorptivity and Sandell's sensitivity of 2.55 x 10(3) l mol(-1) cm(-1) and 0.192 microg cm(-2) per 0.001 absorbance unit, respectively. The method has been successfully applied to the determination of the drug in commercial dosage forms. Statistical comparison of the results with those of a reference method by means of point and interval hypothesis shows excellent agreement and indicates no significant difference in accuracy and precision. Results of analyses were optimized and validated statistically and through recovery studies. The experimental true bias of all samples is smaller than +/-2%.     

紫杉醇新剂型的研究进展

紫杉醇是一种广谱、高效的抗肿瘤药物,但由于其水溶性差,临床上应用的注射剂加入聚氧乙烯蓖麻油以增加紫杉醇的水溶性,但聚氧乙烯蓖麻油在体内会产生严重的毒副作用.为了解决紫杉醇注射剂中聚氧乙烯蓖麻油的毒性问题,开发紫杉醇新剂型是近年来新药研发的热点之一.该文综述了近年来研发的一些紫杉醇新剂型,如乳剂、胶束、环糊精包合物、脂质体、微球、纳米粒和药物释放支架等,并对其可行性进行了分析.     

Selective and validated spectrophotometric methods for the determination of nicorandil in pharmaceutical formulations

Two simple and sensitive validated spectrophotometric methods have been described for the assay of nicorandil in drug formulations. Method A is based on the reaction of the drug with phloroglucinol-sulfanilic acid reagent in sulfuric acid medium to give yellow-colored product, which absorbs maximally at 425 nm. Method B uses the oxidative coupling of 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) with DL- 3,4 - dihydroxyphenylalanine (DL-dopa) in the presence of nicorandil as oxidant in sulfuric acid medium to form an intensely colored product having maximum absorbance at 530 nm. Beer's law is obeyed in the concentration range 2.5 to 50.0 and 1.0 to 15.0 microg mL(-1) with methods A and B, respectively. Both methods have been successfully applied for the analysis of drug in pharmaceutical formulations. The reliability and the performance of the proposed methods are established by point and interval hypothesis and through recovery studies. The experimental true bias of all samples is smaller than +/-2%.     

Spectrophotometric determination of sparfloxacin in pharmaceutical formulations using bromothymol blue

A visible light spectrophotometric method is described for the determination of sparfloxacin in tablets. The procedure is based on the complexation of bromothymol blue 0.5% and sparfloxacin to form a compound of yellow colour with maximum absorption at 385 nm. The Lambert-Beer law was obeyed in the concentration range of 2-12 mg/l. The present study describes a sensitive and accurate method for the determination of the concentration of sparfloxacin in tablets. It was also found that the excipients in the commercial tablet preparation did not interfere with the assay.     

Spectrophotometric determination of piroxicam and tenoxicam in pharmaceutical formulations using alizarin

New spectrophotometric procedures have been established for the quantitation of piroxicam and tenoxicam. The procedures are based on the reaction between the examined drug and alizarin (I), alizarin red S (II), alizarin yellow G (III) or quinalizarin (IV) producing ion-pair complexes which can be measured at the optimum wavelength. The optimization of the reaction conditions is investigated. Beer's law is obeyed in the concentration ranges 0.05-2.40 microg ml(-1), whereas optimum concentration as adopted from Ringbom plots was 0.12-2.25 microg ml(-1). The molar absorptivity, Sandell sensitivity, detection and quantification limits are also calculated. The correlation coefficient was >/=0.9990 (n=10) with a relative standard deviation (R.S.D.) of 相似文献   

Difference spectrophotometric assay of 1,2-diphenolic drugs in pharmaceutical formulations - I. Boric acid reagent

A new procedure is described for the selective determination of drugs containing a 1,2-diphenolic moiety. The assay is based upon the measurement of difference absorbance between two equimolar solutions of the drug in pH 7 phosphate buffer, one of which also contains 0.1 M boric acid. The difference absorbance, which is maximum at about 292 nm, is due to the different spectral characteristics of the boric acid ester of the drug and of the unesterified drug and is proportional to the concentration of the drug. The accuracy, precision, sensitivity and specificity of the procedure are discussed. Applications of the assay are described for adrenaline, isoetharine, isoprenaline, levodopa and methyldopa in pharmaceutical formulations.     

Spectrophotometric analysis of raloxifene hydrochloride in pure and pharmaceutical formulations

Two simple and sensitive spectrophotometric methods (A and B) for the determination of raloxifene hydrochloride in bulk samples and pharmaceutical formulations are described. Method A is based on the oxidation of the drug with ferric chloride and coupling with potassium ferric cyanide. Method B is based on reduction of the drug with Fehling's reagent. Bluish green color formed in method A absorbs at 735 nm and brown color produced in method B absorbs at 430 nm.     

Rapid methods for determination of fluoxetine in pharmaceutical formulations

Two different analytical methods for the quality control of fluoxetine in commercial formulations have been developed and compared: a spectrofluorimetric method and a capillary zone electrophoretic (CZE) method. The fluorescence emission values were measured at λ=293 nm when exciting at λ=230 nm. The CZE method used an uncoated fused-silica capillary and pH 2.5 phosphate buffer as the background electrolyte. The extraction of fluoxetine from the capsules consisted of a simple one-step dissolution with methanol/water, filtration and dilution. Both methods gave satisfactory results in terms of precision; the best results were obtained for the electrophoretic method, with RSD% values always lower than 2.0%. The accuracy was assessed by means of recovery studies, which gave very good results, between 97.5 and 102.6%. Furthermore, both methods also have the advantage of being very rapid.     

SPME-GC determination of potential volatile organic leachables in aqueous-based pharmaceutical formulations packaged in overwrapped LDPE vials

A direct liquid immersion solid-phase microextraction-gas chromatographic (SPME-GC) method was developed and validated for the determination of 11 potential volatile organic compounds that may leach from preprinted foil laminate overwrap into aqueous pharmaceutical formulations filled in low-density polyethylene (LDPE) vials. The target compounds namely, ethanol, acetone, isopropyl alcohol, ethyl acetate, 2-butanone, n-heptane, isopropyl acetate, n-propyl acetate, toluene, diacetone alcohol and 1-propoxy-2-propanol, were suitably extracted from aqueous sample solutions by SPME using a 100-microm PDMS fiber, desorbed inside the GC inlet port, and analyzed using a J&W Scientific DB-1701 (86% polydimethylsiloxane/14% cyanopropylphenyl, 30 m x 0.53 mm i.d., 1.5-microm film thickness) capillary column with FID detection. The variables affecting the SPME absorption and desorption conditions were optimized and discussed. The average recoveries for all analytes varied from about 97.9 to 116.7% with the exception of n-heptane and toluene where the mean recoveries ranged from about 73.6 to 100.0% presumably due to their poor solubility in the aqueous sample matrix. The standard curves for all compounds were linear over the concentration range investigated with coefficient of correlations, r(2)> or =0.98. The detection and quantitation limits ranged from approximately 0.6 ng/ml to 1.7 microg/ml and 5 ng/ml to 4.2 microg/ml, respectively, and the intra- and inter-day precision was considered adequate (R.S.D.< or =16%) for low-level determination of the target analytes in the sample matrix. The method was successfully applied for determination of the target compounds from preprinted foil laminate overwrap in selected aqueous-based pharmaceutical formulations.     

Spectrophotometric determination of acyclovir in some pharmaceutical formulations

A simple and reliable spectrophotometric method has been developed for the determination of acyclovir in pharmaceutical formulations. The method is based on its oxidative coupling reaction with 3-methylbenzothiazolin-2-one hydrazone (MBTH) in the presence of FeCl₃ as an oxidant to produce deep-green colored species measurable at 616 nm. The absorbance-concentration plot is linear over the range 20-200 μg ml⁻¹ with minimum detectability of 1.06 μg ml⁻¹ (4.71×10⁻⁶ M). The molar absorptivity was 9.41×10² l mol⁻¹ cm⁻¹ with correlation coefficient (n=7) of 0.9998. The different experimental parameters affecting the development and stability of the color were studied carefully and optimized. The proposed method was applied successfully to the determination of acyclovir in its dosage forms. The percentage recoveries ±SD (n=9) were 98.63±0.34, 99.61±0.58, 99.35±0.58 and 99.72±0.86 for tablets, ophthalmic ointment and cream, respectively. A proposal of the reaction pathway was presented.     

Spectrophotometric and chromatographic determination of omeprazole in pharmaceutical formulations

The purpose of this study was to determine the stability of the pH sensitive drug, omeprazole, within different solid oral pharmaceutical formulations and to determine whether the addition of antacid and surfactant agents, at varying concentrations, influenced drug stability and release. Spectrophotometric and chromatographic techniques were used for evaluation purposes, giving good results concerning linearity, precision and specificity within the range of concentrations used in this study. However, the results show that the degradation products of omeprazole interfere with spectrophotometric evaluation, making this technique insufficiently selective for omeprazole. On the other hand, liquid chromotography proved to be more sensitive, accurate and precise. Additionally, in an attempt to improve the administration form of the drug, an extemporaneous suspension was designed, which after evaluation proved to be a satisfactory administration vehicle. The best formulation of omeprazole studied is: omeprazole: 0.5%; corn starch 34.2%; aluminum hydroxide 26%; magnesium hydroxide 13%; simple syrup 24.8%; SDS 1%.     

Extractive spectrophotometric methods for the determination of oxomemazine hydrochloride in bulk and pharmaceutical formulations using bromocresol green, bromocresol purple and bromophenol blue

Three simple, sensitive and accurate spectrophotometric methods have been developed for the determination of oxomemazine hydrochloride in bulk and pharmaceutical formulations. These methods are based on the formation of yellow ion-pair complexes between the examined drug and bromocresol green (BCG), bromocresol purple (BCP), and bromophenol blue (BPB) as sulphophthalein dyes in acetate-HCl buffer of pH 3.6, 3.4, and 4.0, respectively. The formed complexes were extracted with dichloromethane and measured at 405 nm for all three systems. The best conditions of the reactions were studied and optimized. Beer's law was obeyed in the concentration ranges 2.0-12, 2.0-13, and 2.0-14 microg mL(-1) with molar absorptivities of 3.2 x 10(4), 3.7 x 10(4), and 3.1 x 10(4) L mol(-1) cm(-1) for the BCG, BCP, and BPB methods, respectively. Sandell's sensitivity, correlation coefficient, detection and quantification limits are also calculated. The proposed methods have been applied successfully for the analysis of the drug in pure form and in its dosage forms. No interference was observed from common pharmaceutical excipients. Statistical comparison of the results with those obtained by HPLC method shows excellent agreement and indicates no significant difference in accuracy and precision.     

Chiral HPLC analysis of formoterol stereoisomers and thermodynamic study of their interconversion in aqueous pharmaceutical formulations

A chiral HPLC method was validated and successfully applied for the determination of formoterol stereoisomers and their inversion products in an aqueous matrix stored at 5–70 °C up to 3 weeks. Analysis was performed on a Chiral-AGP column (100 × 4-mm, 5-μm) using a variable mixture of mobile phase A (50-mM sodium phosphate buffer, pH 7.0) and B (10% v/v IPA) at a flow rate of 1.3 ml min⁻¹, and UV detection at 242 nm. All four formoterol stereoisomers were adequately resolved with acceptable detection and quantitation limits varying from 0.01–0.04 μg/ml and 0.04–0.1 μg/ml, respectively. The method showed acceptable accuracy (≥88%), precision (RSD ≤ 8.5%) and good linearity (r² ≥ 0.9999) over the concentration range investigated. While interconversion at 5 ± 3 °C and 25 ± 2 °C/60% RH ±5% RH was too low to be determined accurately within the study period, chiral inversion of formoterol stereoisomers measured at high temperatures followed the first order rate kinetics and occurred at a single chiral center, resulting in the reversible formation of diastereoisomers, (R,R) ↔ (S,R) and (S,S) ↔ (R,S). No enantiomerization or diastereomerization occurred. There was no significant difference in inversion of the active components in racemic (R,R/S,S)-formoterol fumarate and the single isomer (R,R)-arformoterol tartrate drug formulations, and both drugs are expected to maintain their stereochemical integrity throughout the proposed shelf-life at the recommended storage condition (5 ± 3 °C).     

HPLC analysis of imidazole antimycotic drugs in pharmaceutical formulations

Reversed-phase HPLC on different column packing materials (Hypersil C-18, Spherisorb-CN, Chromspher-B) is used to obtain selective separations of imidazole antimycotic drugs, such as ketoconazole, clotrimazole, tioconazole, bifonazole, isoconazole, econazole, miconazole and fenticonazole. The use of a post-column on-line photochemical reactor is shown to be useful for the enhancement of the sensitivity of the HPLC analysis with UV detection. The proposed HPLC methods are applied to the analysis of commercial dosage forms (creams) with solid-phase extraction (SPE) procedure, using a diol sorbent, being found to be a convenient technique for the sample preparation giving quantitative drug recovery.     

Simultaneous LC determination of paracetamol and related compounds in pharmaceutical formulations using a carbon-based column

A simple, rapid and convenient high performance liquid chromatographic method, which permits the simultaneous determination of paracetamol, 4-aminophenol and 4-chloracetanilide in pharmaceutical preparation has been developed. The chromatographic separation was achieved on porous graphitized carbon (PGC) column using an isocratic mixture of 80/20 (v/v) acetonitrile/0.05 M potassium phosphate buffer (pH 5.5) and ultraviolet detection at 244 nm. Correlation coefficient for calibration curves in the ranges 1–50 μg ml⁻¹ for paracetamol and 5–40 μg ml⁻¹ for 4-aminophenol and 4-chloroacetanilide were >0.99. The sensitivity of detection is 0.1 μg ml⁻¹ for paracetamol and 0.5 μg ml⁻¹ for 4-aminophenol and 4-chloroacetanilide. The proposed liquid chromatographic method was successfully applied to the analysis of commercially available paracetamol dosage forms with recoveries of 98–103%. It is suggested that the proposed method should be used for routine quality control and dosage form assay of paracetamol in pharmaceutical preparations. The chromatographic behaviour of the three compounds was examined under variable mobile phase compositions and pH, the results revealed that selectivity was dependent on the organic solvent and pH used. The retention selectivity of these compounds on PGC was compared with those of octadecylsilica (ODS) packing materials in reversed phase liquid chromatography. The ODS column gave little separation for the degradation product (4-aminophenol) from paracetamol, whereas PGC column provides better separation in much shorter time.