Separation of fibrate-type antihyperlipidemic drugs by capillary electrophoresis and their quantitation in pharmaceuticals.

Six antihyperlipidemic agents-bezafibrate, ciprofibrate, clofibrate, clofibric acid, fenofibrate and gemfibrozil were separated by means of capillary electrophoresis, using unmodified fused silica tubing of 75 microm internal diameter and 87 cm length (65 cm to the UV detector at 227 nm). Migration time and selectivity were examined in differing pH of separation buffer, varying separation voltage and differing temperature. Optimal separation was achieved using 1/15 M phosphate buffer pH 10, 240 V/cm at 25 degrees C. The optimal separation conditions were then used to elaborate the method of quantitation of bezafibrate, ciprofibrate and gemfibrozil in Bezamidin, Lipanor and Gemfibral pharmaceuticals. The clofibric acid was used as internal standard. The calibration curve was constructed from 0.2 to 0.8 mg/ml of each compound and 0.5 mg/ml of internal standard. The calibration data were proved to be linear by Mandel and Lack-of-fit tests. Statistical evaluation of results proved proper recovery of elaborated method (102.42, 97.32 and 101.51%, respectively) and good repeatability (9.51, 5.52 and 11.15%, respectively). The linearity of recovery was also tested by analyzing increasing amount of the samples. Three fortified samples of each drug were also analyzed to perform additional accuracy validation.

Study of the liquid chromatography retention of some fibrate-type antihyperlipidemic drugs on C18 and CN columns: application for quantitation in pharmaceutical formulations.

The 6 antihyperlipidemic agents-bezafibrate, ciprofibrate, clofibrate, clofibric acid, fenofibrate, and gemfibrozil-were separated on octadecyl (C18) and cyano (CN) chemically bonded columns using mobile phases containing phosphate buffer and different amounts of acetonitrile, dioxane, propan-2-ol, methanol, and tetrahydrofuran. Relationships between log k values and mobile phase composition have been examined for these systems. Analysis was performed on a Waters LC system with Merck LichroCART C18 and CN 125 mm columns using a flow rate of 1 mL/min and 227 nm detection. More than one-half of the results fitted Snyder-Soczewinski equations with r >0.995. Separation of all drugs was achieved on the C18 column with a mobile phase containing 45% propan-2-ol in phosphate buffer (pH = 2.145) and on a CN column with 20% acetonitrile in the same buffer. The best mobile phase, containing 45% propan-2-ol, was used to quantitate bezafibrate, ciprofibrate, fenofibrate, and gemfibrozil in pharmaceutical formulations. The active substances were extracted with methanol. The calibration curve was constructed in the 0.1-0.8 mg/mL range for all drugs and provided satisfactory linearity (Lack-of-Fit test and Mandel's test). The recovery function was sufficiently linear in all cases, with an insignificant intercept and slope very close to 1. Accuracy was tested by quantitating 3 fortified samples (50, 100, and 150%), which gave results without significant differences. None of the excipients interfered in the analysis. The recovery was 99.85% for bezafibrate, 99.02% for ciprofibrate, 99.53% for fenofibrate, and 99.92% for gemfibrozil, with relative standard deviation values of 0.63, 1.61, 1.84, and 0.88%, respectively.

Determination of fenofibrate and gemfibrozil in pharmaceuticals by densitometric and videodensitometric thin-layer chromatography.

New thin-layer chromatography (TLC) methods with densitometric and videoscanning detection were elaborated for the quantitative determination of fenofibrate in Fenoratio capsules and gemfibrozil in Gemfibral tablets. Analysis was performed on high-performance TLC diol F254 plates using hexane-tetrahydrofuran (8 + 2, v/v) mobile phase in horizontal DS chambers using the sandwich technique. The active substances were extracted from tablets with methanol. Densitometric assay was performed at 227 nm and videoscanning quantitation at 254 nm. Calibration plots were constructed in range 5-30 microg/spot (20 microL of solutions in different concentrations) for both of the drugs. The calibration data were tested against 3 regression models, and the optimum model was selected (quadratic for videoscanning and nonlinear y = ax(m) + b for the densitometric method, R2 > 0.997 in all cases). Linearity of the methods was tested by spotting different amounts of extracted solution (15-30 mg/spot). The recovery function was sufficiently linear in all cases, with an insignificant intercept and a slope very close to 1. Accuracy was tested by quantitating 3 fortified samples (50,100, and 150% of theoretical), and the results were homogeneous with no significant differences. The recovery in the densitometric assay was 101.42% (total relative standard deviation 10.76%) for fenofibrate and 100.47% (9.7%) for gemfibrozil. Videodensitometry resulted in recoveries of 102.73% (12.59%) and 98.79% (8.56%), respectively. The F-Snedecor test and Student's t-test for 2 means showed no significant differences between the precision and accuracy of both methods.

Determination of citalopram in tablets by capillary zone electrophoresis and by direct and derivative UV-spectrophotometry.

Three rapid, simple and accurate analytical methods for the determination of citalopram in tablets were developed. The capillary zone electrophoresis (CZE) method was carried out using fused silica capillary with 67 mM phosphate buffer pH 7.0 as the background electrolyte, 30 kV of separation voltage and UV detection at 239 nm. The direct spectrophotometric method was performed by measuring the absorbance at the wavelength of 239 nm and derivative spectrophotometric assay was carried out by measuring the value of the second derivative of the spectrum at 210 nm. The linearity range for CZE method was 5-50 microg/mL and for both spectrophotometric methods was 2-12 microg/mL. The recovery in CZE was between 98.6 and 102.4%, in the direct spectrophotometry between 95.0 and 98.0% and in derivative spectrophotometry between 97.6 and 103.3%. The RSD values were between 1.36 and 2.30%, 1.80 and 2.70%, 1.52 and 2.68%, respectively.

LC determination of moclobemide and three metabolites in plasma.

Moclobemide and three metabolites were quantified using 1 ml of plasma and solid-phase extraction with Bakerbond CN column after the addition of nadolol as the internal standard (I.S.). Separation and detection the analysed substances were achieved isocratically with acetonitrile-methanol-0.067 M phosphate buffer pH 2.65-0.4% triethylamine (12.7:1.9:85:0.4, v/v/v/v), a Nova-pak C(8) column and UV detection at 230 nm. The lower limits of quantitation for moclobemide was 10 ng ml(-1), for M1 (Ro 16-3177)-8 ng ml(-1), for M2 (Ro 12-5637)-10 ng ml(-1) and for M3 (Ro 12-8095)-15 ng ml(-1) (as the metabolites). Accuracies calculated of three concentrations in each of three separate runs were between 84.55 and 93.68 for moclobemide, 83.28 and 92.30 for M1, 86.31 and 92.66 for M2 and 88.42 and 93.40 for M3. Precision data within day were between 5.71 and 7.50 for moclobemide, 2.91 and 6.58 for M1, 4.98 and 6.40 for M2 and 0.94 and 4.73 for M3.

Application of UV-derivative spectra for determination of four antihyperlipidaemic drugs in pharmaceutical formulations.

A method for the determination of bezafibrate, ciprofibrate, fenofibrate and gemfibrozil in pharmaceutical formulations by first-, second- and third- derivative spectrophotometry is described, using "peak-peak" and "peak-zero" measurements. The calibration graphs were linear in the range 2-20 microg x mL(-1) for all the compounds investigated. No interference was found from tablet excipients at the selected wavelengths and assay conditions. The developed methods were found to be validated and showed good precision and reproducibility (RSD = 1.57%, 0.78%, 1.45%, and 1.36%, respectively).

Rapid and simple high-performance liquid chromatographic determination of felbamate in serum.

An isocratic high-performance liquid chromatographic method for the quantitation of felbamate in serum is presented. The method is based on protein precipitation with acetonitrile and reversed-phase chromatography with spectrophotometric detection at 210 nm. The separation was performed on a Nova-Pak C18 column and the mobile phase consisted of acetonitrile-water (1:4, v/v). Phenobarbital was applied as an internal standard. The assay was linear over the concentration range 0.5-200.0 microg/ml (r = 0.9999). Intra-day and inter-day precision expressed by relative standard deviation is less than 3%. The percentage of recovery was 98.63 +/- 2.47. The method is suitable for drug level monitoring and for pharmacokinetic studies.

Applications of derivative UV spectrophotometry for the determinations of cetirizine dihydrochloride in pharmaceutical preparations.

A method for the determination of cetirizine dihydrochloride in pharmaceuticals by first-, second-, third- and fourth- order derivative spectrophotometry is described, using "peak-peak" (P-P), and "peak-zero" (P-0) measurements. The calibration curves are linear within the concentration range of 7.5-22.5 microg ml(-1) for cetirizine dihydrochloride. The procedure is simple, rapid and the results are reliable.