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N Erk

Publications and source records attributed to N Erk.

18 recordsLinked to original sources
PubMed2003

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.

Adrenergic beta-Antagonists↗
PubMed2003

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.

Antihypertensive Agents↗
PubMed2002

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.

Anticholesteremic Agents↗
PubMed2001

Analysis of binary mixtures of losartan potassium and hydrochlorothiazide by using high performance liquid chromatography, ratio derivative spectrophotometric and compensation technique.

A new simple, precise, rapid and selective reversed-phase high performance liquid chromatographic (HPLC) and two spectrophotometric methods have been described for resolving binary mixture of losartan potassium and hydrochlorothiazide in the pharmaceutical formulations. The first method, is based on HPLC on a reversed-phase column using a mobile phase 0.01 N sodium dihydrogen phosphate:methanol:acetonitrile (8:2:1 v/v/v) (pH 5.5) with detection at 265.0 nm. The second method, is depend on ratio derivative spectrophotometry, the amplitudes in the first derivative of the ratio spectra at 238.360 nm and at 230.423 nm were selected to simultaneously determine losartan potassium and hydrochlorothiazide in the mixture. The third 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 compensation of either component in the mixture can be achieved, followed by its determination. The accuracy and precision of the methods have been determined and they have been validated by analysing synthetic mixtures containing losartan potassium and hydrochlorothiazide. The methods do not require any separation step. The methods were also applied to the determination of losartan potassium and hydrochlorothiazide in pharmaceutical preparations. The analytical results were quite good in all cases.

Chromatography, High Pressure Liquid↗
PubMed2001

Simultaneous determination of paracetamol and methocarbamol in tablets by ratio spectra derivative spectrophotometry and LC.

The application of the ratio spectra derivative spectrophotometry and high-performance liquid chromatography (HPLC) to the simultaneous determination of paracetamol (PAR) and methocarbamol (MET) in combined pharmaceutical tablets is presented. The spectrophotometric procedure is based on the use of the first derivative of the ratio spectra obtained by dividing the absorbtion spectrum of the binary mixtures by a standard spectrum of one of the compounds. The first derivative amplitudes were measured at 243.0 and 230.3 nm for the assay of PAR and MET, respectively. Calibration graphs were established for 2-30 microg ml for PAR and 2-36 microg/ml for MET in binary mixture. The detection limits for PAR and MET were found 0.097 and 0.079 microg/ml, respectively; while the quantification limits were 0.573 microg/ml for PAR and 1.717 microg/ml for MET. For the HPLC procedure, a reversed-phase column with a mobile phase of methanol-water (60:40, v/v), was used to separate both compounds with a detection of 274.0 nm. Linearity was obtained in the concentration range of 2 300 and 1.5-375 microg/ml for PAR and MET, respectively. The detection and quantification limits were found to be 0.42 and 1.4 microg/ml for PAR and 0.36 and 1.2 microg/ml for MET, respectively. The relative standard deviations were found to be less than 0.52%, indicating reasonable repeatibility of both methods. The proposed methods were successfully applied to the determination of these drugs in commercial tablets.

Acetaminophen↗
PubMed2001

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.

Anti-Infective Agents↗
PubMed2001

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.

Acetaminophen↗
PubMed2001

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.

Antihypertensive Agents↗
PubMed2001

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.

Administration, Topical↗
PubMed2000

Assay of ephedrine hydrochloride and theophylline in pharmaceutical formulations by differential-derivative spectroscopy.

Rapid and accurate binary mixture resolution of ephedrine hydrochloride and theophylline was performed. Differential-derivative spectrophotometry with a zero-crossing measurement technique was used for the quantitative determination of ephedrine hydrochloride and theophylline in pharmaceuticals. Neither sample pretreatment nor separation were required. Linear calibration graphs of differential first derivative values (at 262.4 and 256.3 nm for theophylline and ephedrine hydrochloride, respectively) versus concentration (in the ranges 6.0-40.0 and 100.0-1000.0 microg ml(-1) for theophylline and ephedrine hydrochloride, respectively) were obtained with negligible intercepts. Vierordt's method was also developed for a comparison method. Commercial tablet and laboratory-prepared mixtures containing both drugs were assayed using the developed methods. Both methods showed good linearity, precision and reproducibility.

Bronchodilator Agents↗
PubMed2000

Study on electrooxidation of cefadroxil monohydrate and its determination by differential pulse voltammetry.

In this work electrooxidation of cefadroxil monohydrate was investigated using a glassy carbon electrode depending on pH and supporting electrolyte. It was shown that the direct determination of the substance from capsules and in oral suspension could be made by differential pulse voltammetry (DPV). UV and first derivative UV spectrophotometric methods are also proposed as comparative methods.

Cefadroxil↗
PubMed2000

Quantitative analysis of chlorpheniramine maleate and phenylephrine hydrochloride in nasal drops by differential-derivative spectrophotometric, zero-crossing first derivative UV spectrophotometric and absorbance ratio methods.

Three simple, rapid and accurate methods are described for the simultaneous determination of chlorpheniramine maleate and phenylephrine hydrochloride in two component mixtures. The first method comprised of measurement of difference absorptivities derivatized in first order of a nasal drops in 0.1 N NaOH relative to that of an equimolar solution in methanol at wavelengths of 271.6 and 250.2 nm, respectively. The second method, zero-crossing derivative spectrophotometry, is based on recording the first derivative curves and determining each component using the zero-crossing technique. Using first derivative spectrophotometry, the amplitudes in the first derivative spectra at 246.5 and 238.6 nm were selected to simultaneously determine chlorpheniramine maleate and phenylephrine hydrochloride in the mixture. The presence of identical zero-crossing points for pure drugs and nasal drop solutions established the non-interference of the excipients in the absorption at these wavelengths. Absorbance ratio method was also developed for a comparison method. The proposed procedures were successfully applied to the determination of chlorpheniramine maleate and phenylephrine hydrochloride in nasal drops, with a high percentage of recovery, good accuracy and precision.

Anti-Allergic Agents↗
PubMed1999

Simultaneous determination of hydrochlorothiazide and amiloride hydrochloride by ratio spectra derivative spectrophotometry and high-performance liquid chromatography.

Rapid, precise, accurate and specific ratio spectra derivative spectrophotometry and high-performance liquid chromatographic procedures were described for the simultaneous determination of hydrochlorothiazide and amiloride hydrochloride in combined pharmaceutical dosage forms. For the first method, ratio spectra derivative spectrophotometry, the signals were measured at 285.7 nm for hydrochlorothiazide and at 302.5 nm for amiloride hydrochloride in the mixture, in the first derivative of the ratio spectra. The second method is based on high-performance liquid chromatography (HPLC) on LiChrosorb RP-C18 column (5 microm, 20 cm x 4.6 mm) using 0.025 M orthophosphoric acid (adjusted to pH 3.0 with triethylamine (TEA)), acetonitrile (84:16 v/v) as a mobile phase at a flow rate of 1.2 ml/min(-1). Detection was carried out using a UV detector at 278.0 nm. Commercial sugar-coated and laboratory-prepared mixtures containing both drugs in different proportions were assayed using the developed methods.

Amiloride↗
PubMed1999

Determination of active ingredients in the pharmaceutical formulations containing hydrochlorothiazide and its binary mixtures with benazepril hydrochloride, triamterene and cilazapril by ratio spectra derivative spectrophotometry and vierordt's method.

Procedures were developed for the simultaneous determination of pharmaceuticals in binary mixtures, containing hydrochlorothiazide-benazepril hydrochloride, hydrochlorothiazide triamterene and hydrochlorothiazide cilazapril by ratio spectra derivative spectrophotometry and Vierordt's method. Mean recoveries, relative standard deviations and linearity ranges in calibration graphs of the methods were compared. These procedures were successfully applied to three pharmaceutical formulations for the determination of active ingredients.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1999

Application of derivative-differential UV spectrophotometry and ratio derivative spectrophotometric determination of mephenoxalone and acetaminophen in combined tablet preparation.

A method is presented for the direct determination of mephenoxalone and acetaminophen in combined pharmaceutical dosage forms without prior separation. The first method, derivative-differential spectrophotometry, comprised of measurement of the difference absorptivities derivatized in the first order (deltaD1) of a tablet extract in 0.1 N NaOH relative to that of an equimolar solution in methanol at wavelengths of 289.6 and 252.6 nm respectively. The second method is based on ratio derivative spectrophotometry. The amplitudes in the first derivative of the ratio spectra at 233.5 and 288.9 nm were selected to determine mephenoxalone and acetaminophen in the mixture. The proposed methods, which give thoroughly comparable data, are simple and rapid, and allow one to obtain precise and accurate results.

Acetaminophen↗
PubMed1977

[Not Available].

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History, Modern 1601-↗
PubMed1976

[Not Available].

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History of Medicine↗