Microbiological assay for the determination of telithromycin in tablets

This study describes the development and validation of a microbiological assay, applying the cylinder-plate method, for the determination of the antibiotic telithromycin. The microbiological method consisted of a cylinder-plate agar diffusion assay using Micrococcus luteus ATCC 9341 as the test microorganism. The response graphs for standard and sample solutions were linear (r = 0.9987), and no parallelism deviations were detected in the tested concentrations (0.25, 0.5, and 1.0 microg/mL). The interday precision was 2.67%. Recovery values were between 96.75 and 100.91%. A preliminary stability study of telithromycin showed that the microbiological assay is specific for the determination of telithromycin in the presence of its degradation products. The proposed method allows the quantitation of telithromycin in pharmaceutical dosage form and can be used for drug analysis in routine quality control.     

Microbiological assay for ceftazidime injection

A simple, sensitive, and specific biodiffusion assay for the antibacterial ceftazidime was developed using a strain of Staphylococcus epidermidis (ATCC 12228) as the test organism. Ceftazidime was measured in powder for injection at concentrations ranging from 100 to 400 microg/mL. The calibration graph for ceftazidime was linear (r2 = 1), and the method validation showed that it was precise (relative standard deviation = 0.415) and accurate. The results obtained by biodiffusion assay were statistically calculated by linear parallel model and by means of regression analysis and were verified using analysis of variance. It was concluded that the microbiological assay is satisfactory for in vitro quantification of the antibacterial activity of ceftazidime in pharmaceuticals.     

Microbiological assay for cefoxitin sodium in dosage form

A microbiological assay applying the cylinder-plate method is described for determination of the activity of cefoxitin sodium in injectables. Using a strain of Staphylococcus epidermidis ATCC 12226 as the test organism, cefoxitin sodium was measured in concentrations ranging from 50.0 to 200.0 microg/mL. The validation showed that the method was linear (r = 0.9998), precise (RSD = 0.81%), and accurate. It was concluded that the microbiological assay is satisfactory for quantitation of cefoxitin sodium in injectables.     

微生物法分析天然抗氧化剂性能

建立了微生物抑菌活性纸片试验法，对葛根黄酮、诃子提取物、丹皮酚、竹叶黄酮等4种天然抗氧化剂的抗氧化性能进行了研究。竹叶黄酮、诃子、葛根具有较强的抗单线态氧能力，而丹皮酚抗单线态氧的能力较差。在不同的氧化还原微环境下，天然抗氧化剂可能表现出抗氧化能力，亦可能表现出促氧化能力，二者有着不同的反应机理。微生物抑菌活性纸片法可作为研究较复杂生物环境中抗氧化剂性能的一种简便方法。     

New high-performance liquid chromatographic method for determination of clopidogrel in coated tablets

A new high-performance liquid chromatographic method was developed and validated for clopidogrel determination in pharmaceutical formulations. The system consisted of an ACE 5 octadecylsilane (C18; 150 x 4.6 mm id), 5.0 microm particle size column; methanol-0.1% triethylamine (75 + 25, v/v), pH 5.3, mobile phase at a flow rate of 1.2 mL/min; and a diode array detector set at 220 nm. Specificity, linearity, precision, accuracy, and robustness were the parameters evaluated. The retention time for clopidogrel was 6.8 min. To estimate specificity, an aqueous sample solution was subjected to degradation by ultraviolet light and by acid, alkaline, and oxidation media. The peaks of degradation products did not interfere with the compound signal, and there was no interference when a placebo solution was analyzed. Linearity over a concentration range of 10.0 to 90.0 microg/mL was shown (correlation coefficient = 0.9998). Low values of relative standard deviation indicated the adequate intraday and interday precision. The average recovery was found as 99.16%. In the robustness test, small modifications to the mobile phase composition did not affect the determination of clopidogrel. The proposed method proved to be simple, fast, and cost efficient for the intended use.     

New liquid chromatographic method for determination of rabeprazole sodium in coated tablets

Rabeprazole sodium is a proton pump inhibitor that covalently binds and inactivates the gastric parietal cell proton pump (H+/K+ ATPase). Little has been published about the quantitative determination of this drug. The aim of this research was to develop a new liquid chromatographic method for quantitative determination of rabeprazole in coated tablets. The system consisted of a Hypersil Keystone Betabasic C8 column (250 x 4.6 mm, 5 microm particle size), an isocratic acetonitrile-water (35 + 65) mobile phase at a flow rate of 1.0 mL/min, and a diode array detector set at 282 nm. The following validation parameters were evaluated: linearity, precision, accuracy, specificity, detection and quantitation limits, and robustness. The method showed good linearity in the concentration range of 10-70 microg/mL. The quantitation limit was 2.43 microg/mL, and the detection limit was 0.80 microg/mL. The intra- and interday precision data showed that the method has good reproducibility (relative standard deviation = 1.03). Accuracy and robustness were also evaluated, and the results were satisfactory. The mean recovery was 101.61%. The analysis of a placebo mixture demonstrated the method is also specific.     

First-derivative spectrophotometry in the analysis of rosiglitazone in coated tablets

First-derivative spectrophotometry, applying the peak-zero method, was developed for the determination of rosiglitazone (RSG) in coated tablets. The solutions of standard and sample were prepared in ethanol. Quantitative determination of the drug was performed at 331.4 nm (N = 4; delta lambda = 3.2 nm) and was evaluated for the parameters specificity, linearity, precision, and accuracy. The specificity test showed that there was no interference from excipients commonly found in the commercial pharmaceutical formulation at 331.4 nm. The standard curve showed a correlation coefficient of 0.9997. Precision was demonstrated by a relative standard deviation value of 0.50%. The recovery test resulted in an average of 100.06%, which confirmed the accuracy of the method. The results for first-derivative spectrophotometry (D(1)), liquid chromatography, and micellar electrokinetic chromatography were compared by analysis of variance (ANOVA), and there were no significant differences among these methods. Therefore, D(1) can be easily and directly applied to analyze RSG in coated tablets.     

NMR assay of ephedrine hydrochloride in tablets

A rapid NMR method is described for the determination of ephedrine hydrochloride. The relative standard deviations are 1.5% and 1.2% for the pure drug and tablets respectively. The results for synthetic mixtures and tablets are comparable to those obtained by the B.P. 1973 method. In addition, the NMR spectrum furnishes a specific means of identification of ephedrine.     

Differential pulse voltammetric assay of lercanidipine in tablets

Lercanidipine in ethanol-0.04M Britton-Robinson buffer (20 + 80) gives an irreversible anodic response on a glassy carbon electrode in a broad pH range (2-12) that depends on pH. This signal can be attributed to oxidation of the 1,4-dihydropyridine ring to give the corresponding pyridine derivative. For analytical purposes, differential pulse voltammetry at pH 4 was selected. Under these conditions, good values of both within- and interday reproducibility were obtained, with coefficient of variation (CV) values of 1.56 and 1.70%, respectively, for 10 successive runs. For quantitation, the calibration curve method was used for lercanidipine concentrations ranging from 1 x 10(-5) to 1 x 10(-4) M. The detection and quantitation limits were 1.39 x 10(-5) and 1.49 x 10(-5), respectively. A liquid chromatographic method with electrochemical detection was used for comparison. The voltammetric method showed good selectivity with respect to both excipients and degradation products. The recovery study exhibited a CV of 0.94% and an average recovery of 98.3%, and it was not necessary to treat the sample before the analysis. The method was successfully applied to the individual tablet assay of lercanidipine in commercial tablets.     

Biological assay and liquid chromatographic method for analysis of moxifloxacin in tablets

A microbiological assay and a liquid chromatographic method were validated for quantitation of moxifloxacin in tablets. The microbiological method consisted of a cylinder-plate agar diffusion assay using Micrococcus luteus ATCC 9341 as the test microorganism and phosphate buffer (0.1M, pH 8.0) as the diluent solution. The response graphs for standard and sample solutions were linear (r = 0.9479), and no parallelism deviations were detected in the tested levels of concentration (4.0, 8.0, and 16.0 microg/mL). The interday precision was 2.73%. Recovery values were between 96.25 and 100.5%. The chromatographic analyses were performed using a Shim-pack CLC-ODS column (250 x 4.6 mm, 5 microm) with a mobile phase consisting of (A) a mixture of phosphoric acid (0.17%, v/v) with tetramethylammonium hydroxide (0.05M) and acetonitrile (95 + 5, v/v) and (B) methanol (55 + 45, v/v) adjusted to pH 3.0. The flow rate was 1.0 mL/min, and detection was made at 294 nm. The method was linear in a range from 12.0 to 42 microg/mL (r = 0.9999), and the interday precision was 1.39%. Recovery ranged between 101.9 and 103.81%. Both validated methods were used to quantify the moxifloxacin content in tablets exposed to ultraviolet radiation, and similar results were obtained.     

Microbiological assay of avoparcin in animal feeds and pre-mixes--co-operative study.

A microbiological method for the determination of the antibiotic growth promoter avoparcin in animal feeds and pre-mixes was first published in 1979. The existing method has been applied to new matrices as commercial use of avoparcin has spread. Problems with the existing analytical procedure have been reported, particularly in Germany. This paper identifies the causes of the problems and includes revisions to the existing analytical procedure. The testing of these revisions in co-operative studies with up to five German official laboratories is also reported.     

Argentimetric assay of captopril in bulk drug and in tablets

Three simple, selective and cost-effective procedures for the determination of captopril in bulk drug and in tablets are described. All the procedures make use of silver nitrate as a reagent and involve titrimetry and spectrophotometry as measurement techniques. In titrimetry (Method A), the aqueous solution of the drug is titrated directly with the standard silver nitrate solution to a potassium chromate end-point. In one spectrophotometric method (Method B), the sample solution is treated with excess of silver nitrate and a known amount of methyl orange and the increase in absorbance at 520 nm, caused by a decrease in pH due to release of nitric acid, is measured and related to drug concentration. The other spectrophotometric method (Method C) involves the addition of a measured excess of silver nitrate to the sample solution followed by the determination of residual silver ion by an ion-associate complex formation reaction involving eosin and 1,10-phenanthroline. The decrease in absorbance at 550 nm, which corresponds to Ag⁺ reacted with the drug, is measured and is found to be linearly related to drug concentration. All experimental variables involved in the methods were investigated and optimized. Stoichiometry of the reaction that forms the basis for titrimetry is found. Method A is applicable in the range of 1.0–20.0 mg of drug while methods B and C can be conveniently used in the concentration ranges of 2.5–50.0 and 0.25–4.0 μg ml^?1, respectively. Several optical characteristics such as molar absorptivity, Sandell sensitivity, limits of detection and quantification, and correlation coefficient were calculated. The methods were applied to the analysis of tablets containing captopril. Statistical treatment of the results indicates that the procedures are precise and accurate. The excipients used as additives in tablets did not interfere in the proposed procedures as revealed by the recovery studies.     

Microbiological assay for chemical species of selenium in foods utilizing Escherichia coli formate dehydrogenase

Summary The problems inherent in chemical speciation of selenium in food are being overcome by developing a bioassay which takes advantage of the presence in Escherichia coli of formate dehydrogenase enzymes that require selenium for synthesis. Formate dehydrogenase catalyzes the formation of CO₂ from formic acid, a metabolite of sugar fermentation. Various selenium compounds utilized in formate dehydrogenase production can be quantitated by measuring CO₂ with an Infrared Analyzer. This assay is sensitive at the picomoles/mg level of selenium in food. Linear dose response curves have been generated over several orders of magnitude, extending down to the picomoles/ml range for selenomethionine, selenocystine and sodium selenite. A dose response relationship has been demonstrated to acid hydrolyzates of a wheat gluten reference material (NIST RM 8418) obtained from the National Institute of Standards and Technology.     

Simpler spectrophotometric assay of paracetamol in tablets and urine samples

A very fast, economical and simpler direct spectrophotometric method was investigated for paracetamol (PC) determination in aqueous medium without using any chemical reagents. The method is based on the photo-absorption of the analyte at 243 nm after dissolution in water. The change in structure of PC after addition of water was studied by comparing the corresponding FTIR spectra. Optimization studies were conducted by using a 5 microg ml(-1) standard solution of the analyte. Various parameters studied include, time for stability and measurement of spectra, effect of HCl, NaOH, CH(3)COOH and NH(3) for change in absorbance and shift in spectra, interference by some analgesic drugs and some polar solvents and temperature effect. After optimization, Beer's law was obeyed in the range of 0.3-20 microg ml(-1) PC solution with a correlation coefficient of 0.9999 and detection limit of 0.1 microg ml(-1). The newly developed method was successfully applied for PC determination in some locally available tablets and urine samples. The proposed method is very useful for quick analysis of various types of solid and liquid samples containing PC.     

Optimum operating conditions for manufacturing ibuprofen tablets coated with polyethylene glycol by melt crystallization process

Journal of Thermal Analysis and Calorimetry - The aim of this work is to apply the melt crystallization technology to manufacture ibuprofen tablets coated with polyethylene glycol in a single step....     

The transfer between instruments of a reflectance near-infrared assay for paracetamol in intact tablets

This study compares several correction methods to facilitate the transfer of a validated near-infrared (NIR) assay for paracetamol in intact tablets between two reflectance NIR instruments of the same type. Transfer was defined as the ability to accurately predict the true assay value of a sample measured on a NIR system using an assay developed on a different system, and was assessed using a comprehensive set of statistical tests. Direct electronic transfer of the calibration models, representing the NIR assay, was not possible as a result of a definite residual spectrum between instruments. The use of a correction method based on the standardisation of the material used to record the reference spectrum also proved ineffective. Two methods investigated did succeed, the first employed a response surface calculated between the reflectance values of a set of six certified photometric standards measured on both instruments, with all full range partial least square (PLS) regression models subsequently transferred. The next was correction of the spectra from the second instrument utilising the residual spectrum between the mean sample of the validation set measured on both instruments. Through this approach all PLS regression models and also a single multiple linear regression (MLR) model were transferred. As an outcome of this study guidelines are suggested for the transfer of NIR assays along with the criteria deemed necessary to conclusively prove transfer and justify any correction method utilised. The significant criteria were determined to be the paired t-test with both the UV reference assay data and the original NIR assay data, and comparison of the coefficient of multiple determinations.     

Development of a stability-indicating CE assay for the determination of amlodipine enantiomers in commercial tablets

A simple, accurate, precise and sensitive method using CD for separation and stability indicating assay of enantiomers of amlodipine in the commercial tablets has been established. Several types of CD were evaluated and best results were obtained using a fused-silica capillary with phosphate running buffer (100 mM, pH 3.0) containing 5 mM hydroxypropyl-alpha-CD. The method has shown adequate separation for amlodipine enantiomers from its degradation products. The drug was subjected to oxidation, hydrolysis, photolysis and heat to apply stress conditions. The range of quantitation for both enantiomers was 5-150 microg/mL. Intra- and inter-day RSD (n=6) was <4%. The limit of quantification that produced the requisite precision and accuracy was found to be 5 microg/mL for both enantiomers. The LOD for both enantiomers was found to be 0.5 microg/mL. Degradation products produced as a result of stress studies did not interfere with the detection of enantiomers and the assay can thus be considered stability indicating.