A simple and sensitive chemiluminescence method for the determination of tiopronin for a pharmaceutical formulation

Here we report a rather simple and convenient chemiluminescence (CL) method for the determination of tiopronin. It was based that tiopronin could greatly enhance CL between H₂O₂ and luminol in a basic alkaline solution. Light emission is intense, and even with a simple setup a high sensitivity could be achieved. The linear range was 3 mM–500 nM with a detection limit of 200 nM. Singlet oxygen and hydroxyl radical were suggested to be produced in this reaction and was responsible for the CL of tiopronin. As a preliminary application, this simple method has been successfully applied into the determination of tiopronin in a pharmaceutical formulation.     

Voltammetric assay of Guaifenesin in pharmaceutical formulation

The electrochemical oxidation of Guaifenesin in a pharmaceutical formulation containing Guaifenesin has been carried out in Britton-Robinson buffer (BRB) (0.04 mol L-1) on platinum electrode. Guaifenesin exhibits a well-defined irreversible oxidation peak at 0.924 V/ref. The influence of pH on the oxidation of Guaifenesin was studied in BRB (pH range 2-5). A method for the analysis of Guaifenesin in BRB (0.04 mol L-1, pH 2), which allows quantification over the range 20-60 microg mL-1, was proposed and successfully applied to the determination of Guaifenesin in syrup with mean recovery and relative standard deviation of 103.3% and 1.32%, respectively.     

Development of a simple high performance liquid chromatography (HPLC)/evaporative light scattering detector (ELSD) method to determine Polysorbate 80 in a pharmaceutical formulation

The amount of polysorbate 80 in pharmaceutical formulations affects the product quality and efficacy. A reliable test method is required to quantify the amount of Polysorbate 80 present in the drug product formulations. The test method for the determination of Polysorbate 80 may be used during process development and final product quality assessment. A simple, fast and efficient quantitative method, making use of HPLC-ELSD and a C18 column without sample pretreatment was developed. The developed method demonstrated specificity to polysorbate 80 with high precision as indicated by percent relative standard deviation (%RSD) of 3.0% for six determinations. The accuracy of this method for the determination of polysorbate 80 in a pharmaceutical formulation was demonstrated with an overall recovery of 94.9%.     

Voltammetric determination of cilazapril in pharmaceutical formulations

A sensitive adsorptive stripping voltammetric method for the measurement of cilazapril in 0.04 M Britton-Robinson buffer (pH 9.0) solution was described. The method was based on the adsorptive accumulation of the drug at a hanging mercury drop electrode (HMDE), followed by differential pulse voltammetry. The response was evaluated with respect to pre-concentration time, pH effect, accumulation potential, accumulation time and scan rate. The peak potential was -0.60 V (vs. Ag/AgCl). The peak current was directly proportional to the concentration of cilazapril with a detection limit of 17.6 ng ml(-1) at an accumulation time of 10 s. The reduction process was irreversible and the wave showed adsorptive characteristics. The results were compared to those obtained using a HPLC procedure. A reversed-phase C18e column with aqueous phosphate buffer (pH 3.5; 0.125 M)-acetonitrile (67:33, v/v) mobile phase and benazapril as internal standard was used. UV detector was set at 254 nm. Results obtained in HPLC were comparable to those obtained by adsorptive stripping voltammetric method.     

Voltammetric assay of anti-anginal drug nicorandil in different solvents

Voltammetric behaviour and assay of nicorandil were investigated using square-wave and cyclic voltammetry. Voltammograms in Britton-Robinson (BR) buffer exhibited one well-defined and two merged reduction peaks. The influence of different buffers, electrolytes, pH, scan rates, and concentration of the drug on cathodic peak current was studied. On the basis of electrochemical behaviour of nicorandil, a direct square-wave voltammetric procedure for quantitation of nicorandil has been developed and validated. The proposed square-wave voltammetric method allows quantitation over the range 12.5-62.5 μg mL(-1) with correlation coefficient of 0.992. The limit of quantification and limit of detection were 21.95 μg mL(-1) and 6.58 μg mL(-1) , respectively. Precision and accuracy were also checked and found within limits. The developed square-wave method has also been successfully applied for the determination of nicorandil in pharmaceutical formulations.     

Colorimetric determination of gabapentin in pharmaceutical formulation

Three accurate, simple and precise colorimetric methods for the determination of gabapentin in capsules are developed. The first method is based on the reaction of gabapentin with vanillin (Duquenois reagent) in the presence of McIlvain buffer pH 7.5 and the color developed was measured at 376 nm. The linearity range was found to be 80-360 microg ml(-1). The second is based on the reaction of the primary amino group of gabapentin with ninhydrin reagent in N,N'-dimethylformamide (DMF) medium producing a colored product which absorbs maximally at 569 nm. Beer's law is obeyed in the concentration range 40-280 microg ml(-1) of gabapentin. The third method is based on the reaction of gabapentin with p-benzoquinone (PBQ) to form a colored product with lambda(max) at 369 nm. The products of the reaction were stable for 2 h at 30 degrees C, shifts of the wavelength of maximum absorbance were not observed for up to 24 h after starting the reaction. The absorbance is proportional to gabapentin concentration in the range 80-320 microg ml(-1). The optimum experimental parameters for the reactions have been studied. The validity of the described procedures was assessed. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The suggested procedures could be used for the determination of gabapentin in capsules. The procedures were rapid, simple and suitable for quality control application.     

Polarographic determination of propranolol in pharmaceutical formulation

Propranolol was reacted with nitric acid to give nitropropranolol and was then measured in Britton-Robinson solutions in the pH range 2.0-12.0 by differential-pulse polarography. Nitropropranolol gave rise to a well-resolved differential-pulse polarographic peak at pH 2.0. A linear calibration graph in the range 5.0 x 10(-7)-5.0 x 10(-5) M and a detection limit of 5 nM was obtained. The relative standard deviation was 1.95% (n = 10) at 5 x 10(-6) M. The effect of common exceipient on the peak height was evaluated. The method was applied for the determination of the drug in the tablet dosage form.     

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.     

Reversed-phase ion-pair HPLC determination of some water-soluble vitamins in pharmaceuticals

A reversed-phase ion-pair high-performance liquid chromatografic method (RP-IPC) was developed to assay some water-soluble vitamins in solution dosage forms. Vitamins of the B-group B₁, B₂, B₃, and B₆, including vitamin C were determined in Oligovit^® coated tablets. In Beviplex^® coated tablets the vitamins B₁, B₂, B₃, B₆ and p-aminobenzoic acid were analysed. Hexanesulphonic acid sodium salt and triethanolamine in water–methanol were used as mobile phase with adjusting pH to 2.8 with orthophosphoric acid. Phenol was used as an internal standard. For quantitative simultaneous analysis of vitamins in pharmaceutical formulations, the method of internal standard was used. All parameters for the validation of the method are given.     

Comparison of clinical results of two pharmaceutical products of riboflavin in corneal collagen cross-linking for keratoconus

Background

To compare the 6-month results of two formulations of Riboflavin provided by Sina Darou, Iran, and Uznach, Switzerland, in corneal collagen cross-linking (CXL) for keratoconus patients.

Findings

Considering the results of the previous study about the similarity of the formulations and the active ingredients of the two types of Riboflavin, they were used in the CXL procedure of 60 keratoconic eyes (30 eyes in each group). After 6 months, the mean improvement of UCVA (0.239), BCVA (0.707), and MRSE (0.513) did not differ significantly between the two groups. The mean decrease in max- K (0.731), mean- K (0.264), central corneal thickness (0.759), and Q-value (0.669) did not show any significant difference between the two groups. The two groups had no significant difference in endothelial cell count decrease (0.229). The Sina Darou formulation decreased corneal hysteresis more than the Swiss formulation (P = 0.057) but there were no significant differences in the mean decrease of corneal resistance factor between the two groups (P = 0.117).

Conclusions

Based on the early results, the results of visual acuity, refraction, and corneal topography using Sina Darou and Uznach formulations of Riboflavin showed that both were effective in CXL. However, considering the relatively significant difference in corneal hysteresis changes between the two groups, this study will continue to report the long-term results.     

Quantitation of poloxamers in pharmaceutical formulations using size exclusion chromatography and colorimetric methods

Poloxamers have been used as functional excipients in pharmaceutical products. They function as surfactants, emulsifying agents, solubilizing agents, dispersing agents, and in vivo absorbance enhancer. Despite their wide range of applications, limited analytical techniques have been reported in literature for characterizing poloxamers and few are targeted to quantify poloxamer contents in formulations with desired sensitivity and accuracy. In this paper, two distinct analytical methods for quantifying low levels of poloxamers in pharmaceutical formulations have been developed and optimized: a colorimetric method and a size exclusion chromatography method. The colorimetric method is based on the formation of a colored complex between poloxamers and cobalt(II) thiocyanate in aqueous medium, which has a maximum UV absorbance at 624 nm. The feasibility of this method is product specific. In this report, adequate specificity and sensitivity was demonstrated for only one of the several products tested. The size exclusion chromatography (SEC) method utilizes size exclusion columns with THF as mobile phase and refractive index detection. The SEC method provides a limit of quantitation (LOQ) of 0.005 mg/mL (0.0005%, w/w) and at least three orders of magnitudes of linear range. We applied the SEC method to pharmaceutical products containing 0.3–10% poloxamer 188 or poloxamer 407, such as Avapro, Neurontin, Sudafed and other developmental formulations. The results obtained with the SEC method agreed very well with literature and theoretical values with 97–102% recovery. The SEC method was proven to be widely applicable, accurate, precise and simple to use.     

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.     

Voltammetric determination of copper in selected pharmaceutical preparations--validation of the method

It were established and validated the conditions of voltammetric determination of copper in pharmaceutical preparations. The three selected preparations: Zincuprim (A), Wapń, cynk, mied? z wit. C (B), Vigor complete (V) contained different salts and different quantity of copper (II) and increasing number of accompanied ingredients. For the purpose to transfer copper into solution, the samples of powdered tablets of the first and second preparation were undergone extraction and of the third the mineralization procedures. The concentration of copper in solution was determined by differential pulse voltammetry (DP) using comparison with standard technique. In the validation process, the selectivity, accuracy, precision and linearity of DP determination of copper in three preparations were estimated. Copper was determined within the concentration range of 1-9 ppm (1-9 microg/mL): the mean recoveries approached 102% (A), 100% (B), 102% (V); the relative standard deviations of determinations (RSD) were 0.79-1.59% (A), 0.62-0.85% (B) and 1.68-2.28% (V), respectively. The mean recoveries and the RSDs of determination satisfied the requirements for the analyte concentration at the level 1-10 ppm. The statistical verification confirmed that the tested voltammetric method is suitable for determination of copper in pharmaceutical preparation.     

Kinetic spectrophotometric determination of tramadol hydrochloride in pharmaceutical formulation

Two simple and sensitive kinetic methods for the determination of tramadol hydrochloride are described. The first method is based upon a kinetic investigation of the oxidation reaction of the drug with alkaline potassium permanganate at room temperature for a fixed time at 20 min. The absorbance of the colored manganate ions was measured at 610 nm. The second method is based on the reaction of tramadol hydrochloride with 4-chloro-7-nitrobenzofurazan (NBD-Cl) in presence of 0.1 M sodium bicarbonate. The spectrophotometric measurements were recorded by measuring the absorbance at 467 nm, at fixed time at 25 min on thermostated water bath at 90+/-1 degrees C. All variables affecting the development of the colour have been investigated and the conditions were optimised. The absorbance concentration plots in both methods were rectilinear over the range 5-25 and 50-250 microg ml(-1), for the first and second methods, respectively. The two methods have been applied successfully to commercial capsule and ampoule dosage form. The results obtained are compared statistically with those given by the reference spectrophotometric method. The determination of tramadol hydrochloride by the fixed concentration and rate constant methods is feasible with the calibration equations obtained, but the fixed time method proves to be more applicable.     

LC determination of rosiglitazone in bulk and pharmaceutical formulation

An isocratic reversed phase liquid chromatographic (RP-LC) method has been developed and subsequently validated for the determination of rosiglitazone and its related impurities. Separation was achieved with a Symmetry C18 column and sodium phosphate buffer (pH adjusted to 6.2):acetonitrile (50:50, v/v) as eluent, at a flow rate of 1.0 ml/min. UV detection was performed at 245 nm. The method is simple, rapid, selective and stability indicating. Indole was used as internal standard for the purpose of quantification of rosiglitazone. The described method is linear over a range of 0.45-10 microg/ml for related impurities and 180-910 microg/ml for assay of rosiglitazone. The method precision for the determination of assay and related compounds was below 1.0 and 3.6% RSD, respectively. The mean recoveries of impurities were found to be in the range of 95-102%. The percentage recoveries of Active Pharmaceutical Ingredient (API) from dosage forms ranged from 99.02 to 101.30. The method is useful in the quality control of bulk manufacturing and also in pharmaceutical formulations.     

Voltammetric behaviour of rabeprazole at a glassy carbon electrode and its determination in tablet dosage form

The oxidative behaviour of rabeprazole was studied at a glassy carbon electrode in Britton-Robinson (BR) buffer solutions using cyclic, linear sweep and differential-pulse voltammetry. The oxidation process was shown to be irreversible over the pH range (6.0-11.0) and was diffusion-adsorption controlled. An analytical method was developed for the determination of rabeprazole in BR buffer solution at pH 8.0 as supporting electrolyte. The anodic peak current varied linearly with rabeprazole concentration in the range 1.0 x 10(-6) to 2.0 x 10(-5) M of rabeprazole with a limit of detection of 4.0 x 10(-7) M. Validation parameters, such as sensitivity, accuracy, precision and recovery, were evaluated. The proposed method was applied to the determination of rabeprazole in the tablet dosage form. The results were compared with those obtained by a published high-performance liquid chromatographic method. No difference was found statistically.     

Bioavailability of riboflavin from a gastric retention formulation

A gastric retention formulation (GRF) made of naturally occurring carbohydrate polymers and containing riboflavin was tested in vitro for swelling and dissolution characteristics as well as in fasting dogs for gastric retention. The bioavailability of riboflavin, a drug with a limited absorption site in the upper small intestine, from the GRF was studied in fasted healthy humans and compared to an immediate release formulation. It was found that when the GRF is dried and immersed in gastric juice it swells rapidly and releases its drug content in a zero-order fashion for a period of 24 h. In vivo studies in dogs showed that a rectangular shaped GRF stayed in the stomach of fasted dogs for more than 9 h, then disintegrated and reached the colon in 24 h. Endoscopic studies in dogs showed that the GRF hydrates and swells back to about 75% of its original size in 30 min. These in vivo results correlated with in vitro results. Pharmacokinetic parameters determined from urinary excretion data from six human subjects under fasting conditions showed that bioavailability depended on the size of the GRF. The biostudy indicated that bioavailability of riboflavin from a large size GRF was more than triple that measured after administration of an immediate release formulation. Deconvolved input functions from biostudy data suggest that the large size GRF stayed in the stomach for about 15 h.     

Simultaneous voltammetric determination of nitazoxanide and ofloxacin in pharmaceutical formulation

A simple, sensitive and highly selective electrochemical method was developed for the simultaneous determination of nitazoxanide and ofloxacin in aqueous media (Britton-Robinson buffer, pH-8.36) on a hanging mercury drop electrode (HMDE) using differential pulse polarography (DPP). Using DPP a separation of about 936 mV between the peak oxidation potentials of nitazoxanide and ofloxacin present in binary mixtures was obtained. The quantification limits for the simultaneous determination of nitazoxanide and ofloxacin were 0.083 μg/ml and 0.208 μg/ml, respectively. The proposed method was successfully applied for the simultaneous determination of nitazoxanide and ofloxacin in bulk drug and pharmaceutical tablet formulation.     

PBL与LBL在"药物制剂的设计"教学中的应用比较

目的 探讨以问题为基础的教学法(PBL)在药剂学理论教学中的应用价值。 方法 以湖北医药学院药学专业四年制本科06级学生为研究对象,实施 PBL 教学和讲授为基础(LBL)教学两种教学方法,采用问卷调查和理论考核形式,评价PBL教学法在药物制剂的设计中应用效果和可行性。 结果 参加问卷调查的学生中有 88.6%以上的乐意接受PBL教学法,理论考试结果显示,在知识性考核方面两组成绩比较无显著性差异(P>0.05),而在综合能力考核方面PBL教学组成绩优于对照组(P<0.0     

Spectrophotometric determination of etidocaine in pharmaceutical (dental) formulation

A spectrophotometric method was developed for the determination of etidocaine hydrochloride (EH) in injectable pharmaceutical preparation. The proposal of this work was to develop a rapid, simple, inexpensive, precise and accurate visible spectrophotometric method. The method is based on the formation of the ion-pair complex by the EH reaction with bromocresol green in the pH 4.6 which after chloroform extraction gives a yellow color that in basic medium change to blue color and exhibits a maximum absorbance at 625 nm. The calibration graph was linear over the range 2.0-6.0 microg ml(-1) EH calculated on the final yellow solution. The R.S.D. of the slope of the four lines was 0.73%. This method can be applied to injectable pharmaceutical preparation dosage studied.