Voltammetric and HPLC determination of dorzolamide hydrochloride in eye drops

The behaviour of dorzolamide hydrochloride (DOR) was investigated at a glassy carbon electrode in different buffer systems using cyclic (CV), linear sweep (LSV) and differential pulse voltammetry (DPV). The oxidation process was found to be irreversible over the pH range studied (2.0-8.0) and was shown to be diffusion controlled. An analytical method with adequate precision and accuracy was developed for the determination of DOR in Britton-Robinson buffer (BRb) at pH = 3.06 containing 10% methanol as supporting electrolyte. The peak current varied linearly with DOR concentration in the range 4.0 x 10(-5)-6.0 x 10(-4) M. Furthermore, a HPLC method with diode array detection was developed. A calibration graph was established for 1.1 x 10(-6)-1.9 x 10(-4) M of DOR. The procedures were successfully applied for the determination of the drug in eye drops.

Differential pulse anodic voltammetric determination of pantoprazole in pharmaceutical dosage forms and human plasma using glassy carbon electrode

Pantoprazole is used as an anti-ulcer drug through inhibition of H(+), K(+)-adenosine 5(')-triphosphatase in gastric parietal cells. It reduces the gastric acid secretion regardless of the nature of stimulation. The use of differential pulse voltammetry for the determination of pantoprazole in pharmaceutical dosage forms and human plasma using a glassy carbon electrode has been examined. The best voltammetric response was reached for a glassy carbon electrode in Britton-Robinson buffer solution of pH 5.0 submitted to a scan rate of 20.0 mVs(-1) and a pulse amplitude of 50.0 mV. This electroanalytical procedure was able to determine pantoprazole in the concentration range 6.0 x 10(-6)-8.0 x 10(-4)M. Precision and accuracy of the developed method was checked with recovery studies. The limit of detection and limit of quantitation were found to be 4.0 x 10(-7) and 9.0 x 10(-7)M, respectively. Rapidity, precision, and good selectivity were also found for the determination of pantoprazole in pharmaceutical dosage forms and human plasma. For comparative purposes high-performance liquid chromatography with a diode array and UV/VIS detection at 290.0 nm determination also was developed.

Rapid and simple methods for quantitative analysis of some antidepressant in pharmaceutical formulations by using first derivative spectrophotometry and HPLC

Two rapid, simple and accurate first derivative spectrophotometry and HPLC method for the determination of nefazodone hydrochloride and sertraline hydrochloride in pharmaceutical formulations are discussed. The first one is a derivative spectrophotometric procedure and the second one is based on a HPLC method with a UV detector. In the first method, first derivative spectrophotometry, nefazodone hydrochloride or sertraline hydrochloride by measurement of their first derivative signals at 241.8-256.7 nm (peak-to-peak amplitude), or 271.6-275.5 nm (peak-to-peak amplitude), respectively. Calibration graphs were established for 10.0-42.0 microg ml(-1) nefazodone hydrochloride, or 8.0-46.0 microg ml(-1) sertraline hydrochloride. In the other method, HPLC, the UV detection was carried out at 265.0 nm (nefazodone hydrochloride) and 270.0 nm (sertraline hydrochloride). The samples were chromatographed on a Supercosil RP-18 column. The mobile phases were methanol:acetonitrile:phosphate buffer at pH 5.5 (10:50:40 v/v/v) (nefazodone hydrochloride) and methanol:phosphate buffer at pH 4.5 (20:80 v/v) (sertraline hydrochloride). The results obtained from first derivative spectrophotometric method were comparable with those obtained by using HPLC. It was concluded that both the developed methods are equally accurate, sensitive, and precision could be applied directly and easily to the pharmaceutical formulations of nefazodone hydrochloride and sertraline hydrochloride, respectively.

Application of first derivative UV-spectrophotometry and ratio derivative spectrophotometry for the simultaneous determination of candesartan cilexetil and hydrochlorothiazide

Two-component mixtures of candesartan cilexetil (CAN) and hydrochlorothiazide (HYD) were assayed by first derivative and ratio derivative spectrophotometry. The first method depends on zero-crossing and peak to base measurement. The first derivative amplitudes at 270.1 and 255.5 nm were selected for the assay of (CAN) and (HYD), respectively. The second method depends on first derivative of the ratio spectra by division of the absorption spectrum of the binary mixture by a normalized spectrum of one of the components and then calculating the first derivative of the ratio spectrum. The first derivative of the ratio amplitudes at 236, 250, 232, 267 and 280 nm were selected for the determination of (CAN) and (HYD), respectively. Calibration curves were established for 6.0-38.0 microg x ml(-1) for (CAN) and 4.0-28.0 microg x ml(-1) for (HYD) in binary mixtures. Good linearity, precision and selectivity were found, and the two methods were successfully applied to the pharmaceutical dosage form containing the above-mentioned drug combination without any interference by the excipients.

Extractive spectrophotometric methods for determination of lercanidipine

Extractive spectrophotometric methods are described for the determination of lercanidipine (LER) either in pure form or in pharmaceutical formulations. The methods involve formation of coloured chloroform extractable ion-pair complexes with bromothymol blue (BTB) and bromocresol green (BCG) in acidic medium. The extracted complexes showed absorbance maxima at 417 and 416 nm for BTB and BCG, respectively. The optimization of the reaction conditions was investigated. Beer's law is obeyed in the concentration ranges 6.0-42.0 microg x ml(-1) or 7.1-43.8 microg x ml(-1) with BTB or BCG, respectively. The composition of the ion-pairs was found to be 1:1 by Job's method. The specific absorptivities, molar absorptivities, Sandell sensitivities, standard deviations and percent recoveries were evaluated. Also, LER was determined by measurement of its first derivative signals at 245 nm. Calibration graph was established for 4.2-58.0 microg x ml(-1) of LER. The methods have been applied to the determination of drug in commercial tablets. Results of analysis were validated. No interferences were observed from common pharmaceutical adjuvants.

Voltammetric and HPLC techniques for the determination of paroxetine hydrochloride

The antidepressant agent paroxetine hydrochloride (POT) was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and osteryoung square wave voltammetry (OSWV). A sensitive method is described for the determination of POT in its pure form and in human plasma. The linear relationship between concentration and peak current permits the quantification of POT by CV, DPV and OSWV in the concentration range of 2 x 10(-5) - 8 x 10(-4) M. Applicability to tablets and human plasma analysis has been illustrated. Furthermore, a HPLC method with diode array detection was developed. Linearity was established between 2 x 10(-7) - 6 x 10(-5) M for POT. The described methods were successfully employed with high degrees of precision and accuracy for the estimation of total drug content in human plasma and pharmaceutical dosage forms of POT.

Three new spectrophotometric methods applied to the simultaneous determination of hydrochlorothiazide and irbesartan

This work involves the simultaneous determination of hydrochlorothiazide and irbesartan in a binary mixture without previous separation by three new analytical methods. The first method, based on compensation technique, is presented for the derivative spectrophotometric determination of binary mixtures with overlapping spectra. By using ratios of the derivative maxima or the derivative minimum, the exact contribution of either component in the binary mixture can be measured and the amounts quantified. The second method uses of the first derivative of the ratio spectra. The ratio spectra were obtained by dividing the absorption spectra of the binary mixture by that of one of the components. The amplitudes in the first derivative of the ratio spectra at 231, 266, 279, 238 and 248 nm were selected to determine hydrochlorothiazide and irbesartan in binary mixtures. The concentration of the other components are then determined from their respective calibration graphs treated similarly. With the third method, the absorbance ratio method, the determination of hydrochlorothiazide and irbesartan was performed using the absorbances read at 272 nm, 241 nm and 263 nm in the zero-order spectra of their mixture. The absorbance ratio was also developed as a comparison method. The three methods are simple, accurate, rapid and require no preliminary separation steps and can, therefore, be used for routine analysis of both drugs in quality control laboratories.

Rapid and sensitive HPLC method for the simultaneous determination of dorzolamide hydrochloride and timolol maleate in eye drops with diode-array and UV detection

A rapid and sensitive HPLC method has been developed for the simultaneous determination of dorzolamide hydrochloride and timolol maleate. The drugs were monitored with a diode-array detector at two fixed wavelengths (lambda = 250.0 nm for dorzolamide hydrochloride and 300.0 nm for timolol maleate). Liquid chromatography was performed on a RP-YMC pack ODS A-132 C18 (5 microm, 15 cm x 6.0 mm) column and the mobile phase consisted of an acetonitrile: phosphate buffer (pH 2.5): methanol (5:85:10 v/v/v) mix and a flow rate of 1.2 ml x min(-1). The linearity of the method ranged between 4.0-45.0 microg x ml(-1) for dorzolamide hydrochloride and and 2.0-20.6 microg x ml(-1) for timolol maleate in binary mixture. The procedure was successfully applied to the determination of these compounds in pharmaceutical preparations and gave a high recovery, good accuracy and precision without any interference by the excipients.

Simultaneous determination of irbesartan and hydrochlorothiazide in human plasma by liquid chromatography

A simple, selective, sensitive and precise high-performance liquid chromatographic plasma assay for the antihypertensive drugs, irbesartan and hydrochlorothiazide is described. Good chromatographic separation was achieved using a Supelcocil C(18) (5 micrometer 15 cmx4.6 mm) column and a mobile phase consisting of 10 mM potassium dihydrogen phosphate:methanol:acetonitrile (5:80:15 v/v/v) (pH:2.5) while at a flow-rate of 1.0 ml min(-1). Irbesartan and hydrochlorothiazide were detected at 275 nm and were eluted 5.8 and 7.8 min, respectively, after injection. No endogenous substances were found to interfere. The method utilizes protein precipitation with acetonitrile as the only sample preparation involved prior to reversed-phase high-performance liquid chromatography. No internal standard was required. Linearity range for irbesartan and hydrochlorothiazide was 10.0-60.0 microgram ml(-1) and 4.0-20.0 microgram ml(-1), respectively. The determination of intra- and inter-day precision (RSD) was less than 2.5 and 3.5%, at all concentration levels, while the inter- and intra-day accuracy (% difference) was less than 4.9-6.2%. This method is being used in a therapeutic drug monitoring service to quantitate these therapeutic agents in patients for pharmacokinetic studies.

Mucoadhesive microspheres containing gentamicin sulfate for nasal administration: preparation and in vitro characterization

In this study, suitable microsphere formulations were designed in order to provide the absorption of a high polar drug through nasal mucosa. For this purpose, gentamicin sulfate (GS) was chosen as a model drug and used at different drug/polymer ratios in the microsphere formulations. The microspheres were prepared by spray drying technique. Hydroxypropyl methylcellulose was used as a mucoadhesive polymer in the formulations to increase the residence time of the microspheres on the mucosa. Sodium cholate was added into the formulations for increasing the absorption of GS through nasal mucosa. The in vitro characteristics of the microspheres were determined. The microspheres were evaluated with respect to the particle size, production yield, encapsulation efficiency, shape and surface properties, drug-polymer interaction, mucoadhesive property, in vitro drug release and suitability for nasal drug delivery.

Rapid spectrophotometric method for quantitative determination of simvastatin and fluvastatin in human serum and pharmaceutical formulations

A spectrophotometric method has been developed and applied to the determination of simvastatin and fluvastatin in human serum and in tablets. Simvastatine and fluvastatin were determined by measurement of their first derivative signals at 241.6, 245.9, 249.1 nm (for simvastatin) and 259.6 nm (for fluvastatin), respectively. Calibration curves were linear and the ranges of quantification were 12.0-28.0 micrograms.ml-1 for simvastatin and 10.0-28.0 micrograms.ml-1 for fluvastatin. The procedure was successfully applied to the determination of these compounds in pharmaceutical formulations as well as in human serum with a high percentage of recovery, good accuracy and precision, and without measurable interference by the excipients.

Determination of theophylline and ephedrine HCL in tablets by ratio-spectra derivative spectrophotometry and LC

Two methods are described for the determination of theophylline (THP) and ephedrine hydrochloride (EPH) in combined pharmaceutical tablet forms. The first method depends on the use of the first derivative of the ratio-spectra obtained by dividing the absorption spectrum of binary mixtures by a standard spectrum of one of the compounds. The first derivative amplitudes at 231.8 and 250.3 nm were selected for the assay of THP and EPH, respectively. Calibration graphs were established for 20-180 microg ml(-1) for THP and 10-50 microg ml(-1) for EPH. The second method is based on high-performance liquid chromatography on a reversed-phase column using a mobile phase of methanol-water (40+60,v/v) (pH 3) with detection at 217 nm. Linearity was obtained in the concentration range of 5-150 microg ml(-1) for THP and 15-75 microg ml(-1) for EPH. The detection limits for THP and EPH were 0.73 and 0.92 microg ml(-1) by ratio-spectra derivative spectrophotometry and 0.59 and 0.86 microg ml(-1) by HPLC, respectively. The proposed methods were successfully applied to the determination of these drugs in laboratory-prepared mixtures and in tablets. The relative standard deviations were found to be less than 1.5%, indicating reasonable repeatibility of both methods.

Simultaneous determination of dorzolamide HCL and timolol maleate in eye drops by two different spectroscopic methods

Two-component mixtures of dorzolamide hydrochloride and timolol maleate were assayed by first derivative and ratio derivative spectrophotometric methods. The first method, derivative spectrophotometry, by the zero-crossing measurements, was used due to the drugs closely overlapping absorption spectra. Linear calibration graphs of first derivative values at 250.3 nm for dorzolamide hydrochloride and 315.8 nm for timolol maleate. The second method, is based on ratio first derivative spectrophotometry, the amplitudes in the first derivative of the ratio spectra at 242.9 and at 223.5 nm were selected to determine dorzolamide and timolol maleate in the binary mixture. Calibration graphs were established for 8.0-30.0 microg ml(-1) for dorzolamide hydrochloride and 3.0-24.6 microg ml(-1) for timolol maleate in binary mixture. Good linearity, precision and selectivity were found, and the proposed methods were applied successfully to the pharmaceutical dosage from containing the above-mentioned drug combination without any interference by the excipients. Vierordt's method was also developed for a comparison method.

Simultaneous determination of fosinopril and hydrochlorothiazide in pharmaceutical formulations by spectrophotometric methods

Three new spectrophotometric procedures for the simultaneous determination of fosinopril and hydrochlorothiazide are described. The first method, derivative-differential spectrophotometry, comprised of measurement of the difference absorptivities derivatized in the first-order (DeltaD(1)) of a tablet extract in 0.1 N NaOH relative to that of an equimolar solution in methanol at wavelengths of 227.6 and 276.4 nm, respectively. The second method, depends on the application ratio spectra derivative spectrophotometric method to resolve the interferance due to spectral overlapping. The analytical signals were measured at 237.9, 243.8 nm for fosinopril and 262.4, 269.3 and 278.6 nm for hydrochlorothiazide in the binary mixture, in the first derivative of the ratio spectra of the mixture solutions in methanol. Calibration graphs were established for 4.0-50.0 microg ml(-1) fosinopril and 2.0-14.0 microg ml(-1) hydrochlorothiazide in binary mixture. The third method, absorbance ratio method, the determination of fosinopril and hydrochlorothiazide was performed by using the absorbances read at 210.0, 219.5 and 271.7 nm in the zero-order spectra of their mixture. The developed methods were compared with absorbance ratio method. Application of the suggested procedures were successfully applied to the determination of this compound in synthetic mixtures and in pharmaceutical preparations, with high percentage of recovery, good accuracy and precision.

The effect of various root canal sealers on India ink and different concentrations of methylene blue solutions

In this study, the effect of different root canal sealers on 1%, and 2% methylene blue (MB) solutions and India ink were analyzed using spectrophotometry. One hundred and twelve specimens were used in this study. One hundred and five plastic tubes were filled with Sealapex, Endomethasone, Sultan, AH Plus or Ketac Endo. Twenty-one plastic tubes were used for each group. Seven plastic tubes were not filled, serving as controls. Seven specimens were taken from each group randomly and immersed in 0.8 ml 1% MB, 2% MB or black India ink. The optical density of the solutions after 0, 24, 48 and 72 hours of immersion was measured in a spectrophotometer at 416 nm. The optical density (OD) of the solutions was stable for the control group. The OD values for the 1% MB solutions were increased in the Sealapex and Sultan groups. The OD values for the 2% MB solutions were also increased for Sealapex and AH Plus. OD values were decreased for all India ink groups. The change in OD values relating to each time interval was statistically analyzed for each test material using two-way ANOVA. In the dye leakage studies, India ink, when compared to MB solutions, was a more reliable tracer as no dissolution of the root canal sealers occurred in contact with India ink.

Comparison of spectrophotometric and an LC method for the determination perindopril and indapamide in pharmaceutical formulations

A new sensitive, simple, rapid and precise reversed-phase high performance liquid chromatographic (HPLC) and two spectrophotometric methods have been developed for resolving binary mixture of perindopril and indapamide in the pharmaceutical dosage forms. The first method is based on HPLC on a reversed-phase column using a mobile phase of phosphate buffer pH 2.4 and acetonitrile (7:3 v/v) was used. Linearity range for perindopril and indapamide was 5.0-70.0 and 8.0-35.0 microg ml(-1). In the second method, the first derivative spectrophotometry with a zero-crossing technique of measurement is used for the simultaneous quantitative determination of perindopril and indapamide in binary mixtures without previous separation step. Linear calibration graphs of first derivative values at 225.7 and 255.4 nm for perindopril and indapamide, respectively. The third method is based on ratio derivative spectrophotometry, the amplitudes in the first derivative of the ratio spectra at 226.5 and at 255.3 nm were selected to determine perindopril and indapamide in the binary mixture. All the proposed methods showed good linearity, precision and reproducibility. The proposed methods were successfully applied to the pharmaceutical dosage forms containing the above-mentioned drug combination without any interference by the excipients.

The rapid quantitative analysis of phenprobamate and acetaminophen by RP-LC and compensation technique

For the analysis of phenprobamate and acetaminophen in combination, the main analytical methods used were spectrophotometric compensation technique and Vierordt's method with high performance liquid chromatography, used as an analytical reference method. The first procedure for the simultaneous quantitative determination phenprobamate and acetaminophen by high performance liquid chromatographic (HPLC) method was proposed. The method was standardized using a LiChrosorb RP18-5 column, methanol-water-formic acid (120:80:1 v/v), apparent pH 4.25 with triethylamine, as mobil phase and UV detection at 254 nm. The peak area response versus concentration was linear in a concentration range from 4 to 28 microg ml(-1) of phenprobamate and from 4 to 30 microg ml(-1) for acetaminophen. The correlation coefficients were 0.9999 for phenprobamate and 0.9987 for acetaminophen. The second procedure, based on the compensation technique, is presented for the derivative spectrophotometric determination of binary mixtures with overlapping spectra. The proposed methods, which give thoroughly comparable data, are simple and rapid and allow precise and accurate results.

Spectrophotometric resolution of metronidazole and miconazole nitrate in ovules using ratio spectra derivative spectrophotometry and RP-LC

Metronidazole and miconazole nitrate in ovules was determined by ratio spectra derivative spectrophotometry and by high-performance liquid chromatography (HPLC). The first method depends on ratio spectra first derivative spectrophotometry, by utilizing the linear relationship between substances concentration and ratio spectra first derivative peak amplitude. The ratio first derivative amplitudes at 242.6 [(1)DD(242.6)], 274.2 [(1)DD(274.2))] 261.8 [(1)DD(261.8))] 273.5 [(1)DD(273.5))]and 281.5 [(1)DD(281.5)] nm were selected for the assay of metronidazole and miconazole nitrate, respectively. The second method is based on high-performance liquid chromatography on a reversed-phase column using a mobile phase of methanol-water-phosphoric acid (30:70:0.20 v/v) (pH 2.8) with programmable detection at 220.0 nm. The minimum concentration detectable by HPLC was 0.9 microg ml(-1) for metronidazole and 0.3 microg ml(-1) for miconazole nitrate and by ratio derivative spectrophotometry 4.0 microg ml(-1) for metronidazole and 0.5 microg ml(-1) for miconazole nitrate. The proposed procedures were successfully applied to the simultaneous determination of metronidazole and miconazole nitrate in ovules with a high percentage of recovery, good accuracy and precision.