Isoabsorptive Point Research Articles

DEVELOPMENT AND VALIDATION OF SPECTROPHOTOMETRIC METHODS FOR THE SIMULTANEOUS ESTIMATION OF MICONAZOLE NITRATE AND METRONIDAZOLE IN BULK POWDER FORM

Simple, precise, accurate and economical spectrophotometric methods have been developed for s imultaneous determination of Miconazole nitrate (MIZ) and Metronidazole (MNZ) in their bulk powder form. Method (I) is simultaneous equation method and method (II) is absorbance ratio method. This is based on measurement of absorbance at two wavelengths 31 8.8 nm and 279 nm, λ max of Metronidazole and Miconazole nitrate in pH 4.0 phosphate buffers. Both the drugs obeyed Beer - Lambert’s law in the concentration range of 5 - 30 µg/mL for Metronidazole and 100 - 600 µg/mL for Miconazole nitrate. The high values of co rrelation coefficient (R 2 ) indicated good linearity of calibration curve for both the drugs. The second method i.e. absorbance ratio method which invo lves the formation of Q - absorbance equation using the respective absorptivity values at 283 nm (isoabsorpt ive point) and 279 nm (λ max of miconazole nitrate); accuracy , precision and recovery studies of the developed methods have been carried out in order to confirm their accuracy.

Spectrodensitometric determination of some pharmaceutical mixtures containing proton pump inhibitors

Two ultraviolet (UV)-spectrodensitometric methods were proposed for the separation and determination of binary and ternary mixtures containing proton pump inhibitors (PPIs). Method A was developed for the assay of omeprazole, panoprazole, rabeprazole, and lansoprazole in binary mixtures with domperidone (DOM) using their isoabsorptive points. Method B was developed for the determination of a ternary mixture containing omeprazole, tinidazole, and clarithromycin. It depends on using malonic acid-acetic anhydride as a spraying reagent to form yellow color (for omeprazole) and dark brown color (for clarithromycin) that are measured at λmax = 350 nm and λmax = 492 nm, respectively, while tinidazole was measured by UV at λmax = 310 nm. For method A, Beer’s law was obeyed for all studied PPIs and domperidone in the concentration range of 180–1440 and 120–720 ng spot−1, respectively. The detection limits for proton pump inhibitors and domperidone were 48.05–73.45 and 30.74–32.50 ng spot−1, respectively, and the q...

Spectrophotometric methods for simultaneous determination of ternary mixture of amlodipine besylate, olmesartan medoxomil and hydrochlorothiazide

Four, accurate, precise, and sensitive spectrophotometric methods are developed for the simultaneous determination of a ternary mixture containing amlodipine besylate (AM), olmesartan medoxomil (OL) and hydrochlorothiazide (HZ), where AM is determined at its λmax 364.6nm (0D), while (OL) and (HZ) are determined by different methods. Method (A) depends on determining OL and HZ by measuring the second derivative of the ratio spectra (2DD) at 254.4 and 338.6nm, respectively. Method (B) is first derivative of the double divisor ratio spectra (D-1DD) at 260.4 and 273.0nm for OL and HZ, respectively. Method (C) based on successive spectrophotometric resolution technique (SSRT). The technique starts with the ratio subtraction method then measuring OL and HZ at their isoabsorptive point at 260.0nm, while HZ is measured using the amplitude of first derivative at 335.2nm. Method (D) is mean centering of the ratio spectra (MCR) at 252.0nm and 220.0nm for OL and HZ, respectively. The specificity of the developed methods is investigated by analyzing laboratory prepared mixtures containing different ratios of the three drugs and their combined dosage form. The obtained results are statistically compared with those obtained by the official or reported methods, showing no significant difference with respect to accuracy and precision at p=0.05.

Development and Validation of Spectrophotometric Methods for Simultaneous Estimation of Valsartan and Hydrochlorothiazide in Tablet Dosage Form

Two UV-spectrophotometric methods have been developed and validated for simultaneous estimation of valsartan and hydrochlorothiazide in a tablet dosage form. The first method employed solving of simultaneous equations based on the measurement of absorbance at two wavelengths, 249.4 nm and 272.6 nm, λmax for valsartan and hydrochlorothiazide, respectively. The second method was absorbance ratio method, which involves formation of Q-absorbance equation at 258.4 nm (isoabsorptive point) and also at 272.6 nm (λmax of hydrochlorothiazide). The methods were found to be linear between the range of 5–30 µg/mL for valsartan and 4–24 μg/mL for hydrochlorothiazide using 0.1 N NaOH as solvent. The mean percentage recovery was found to be 100.20% and 100.19% for the simultaneous equation method and 98.56% and 97.96% for the absorbance ratio method, for valsartan and hydrochlorothiazide, respectively, at three different levels of standard additions. The precision (intraday, interday) of methods was found within limits (RSD<2%). It could be concluded from the results obtained in the present investigation that the two methods for simultaneous estimation of valsartan and hydrochlorothiazide in tablet dosage form are simple, rapid, accurate, precise and economical and can be used, successfully, in the quality control of pharmaceutical formulations and other routine laboratory analysis.

Superior spectrophotometric method for determination of a ternary mixture with overlapping spectra

Ambroxol hydrochloride (AMB), guaifenesin (GUF) and theophylline (THP) are co-formulated together for treatment of common cold and influenza. A newly developed spectrophotometric method; namely; ratio isoabsorptive point and ratio difference in subtracted spectra (RIDSS) spectrophotometric method was applied for resolving this ternary mixture with overlapping spectra in two steps. The proposed method is based on dividing the ternary mixture of the studied drugs by the spectrum of AMB to get the division spectrum, from which concentration of AMB can be obtained by measuring the amplitude values in the plateau region at 310 nm. Then the amplitude value of the plateau region at 310 nm was subtracted from the division spectrum and THP concentration was obtained by measuring the difference in amplitude values at 235 and 268 nm (corresponding to zero difference of GUF) while the total concentration of THP and GUF in the mixture was measured at their isoabsorptive point in the division spectrum at 235 nm (Aiso). GUF concentration is then obtained by subtraction. Validity of the method was tested by application to laboratory prepared mixtures and pharmaceutical formulations containing the studied drugs. Statistical comparison between the results of the proposed method and those of the reported HPLC method showed no significant difference.

Simultaneous estimation of etodolac and thiocolchicoside in bulk and in tablet formulation by UV-spectrophotometry

Two simple, rapid and reproducible simultaneous equation and Q-Analysis UV-Spectrophotometric methods have been developed for simultaneous estimation of Etodolac (ETO) and Thiocolchicoside (THC) in combined tablet dosage form. The methods involved solving simultaneous equations and Q-value Analysis based on measurement of absorbance at wavelengths, 223 (?max of ETO), 259.4 nm (?max of THC) and 236 nm (Iso-absorptive point). Linearity was found in the concentration range of 1-6 ?g/mL and 4 - 24 ?g/mL for ETO & THC respectively with coefficient correlation 0.9998 & 0.9992. The amount of drugs estimated by proposed methods are in excellent agreement with label claimed. Further-more, the methods were applied for the determination of ETO and THC in spiked human urine. The degradation behavior of ETO and THC was investigated under acid hydrolysis, alkali hydrolysis, photo and oxidative degradation. The samples subsequently generated were used for degradation studies using the developed method. Thiocolchicoside was found to degrade extensively under alkali hydrolysis and unaffected by other stress conditions while ETO was found to be stable in all stress conditions. The methods were validated according to ICH guidelines. The method, suitable for routine quality control, has been successfully applied to the determination of both drugs in commercial brands of tablets.

Stability indicating spectrophotometric methods for determination of Tiemonium methylsulphate in the presence of its degradation products

Simple, selective and sensitive stability indicating spectrophotometric methods have been developed and validated for Tiemonium methylsulphate (TIM) determination in pharmaceutical dosage form. Method A, isoabsorptive point comprised of measurement the total content of the mixture of TIM and its acid degradation product at 250 nm, while the content of acid degradation product was determined by measuring the peak amplitude of the 2 D at 295.6nm, then TIM concentration can be determined by subtraction. Method B, the first derivative of ratio spectra was applied by measuring amplitudes of TIM at 224.4 nm and 247.2 nm using 20µg/mL of acid degradation product as a divisor. Method C is the ratio subtraction method. While method D is based on the measurement of first derivative amplitudes of TIM at the zero crossing point of its oxidative degradation product at 250 nm. The percentages mean accuracy for TIM was 100.39±0.33 for method A, 100.59±0.57 and 100.40±0.56 for B, 100.47±0.54% for C and 100.24±0.58% for D methods. The developed methods were validated as per International Conference of Harmonization guidelines. Furthermore, elucidation of the degradation pathway is described based on the use of the infrared spectroscopy and HPLC/MS techniques.

A New Analytical Q-Absorbance Ratio Method Development and Validation for Simultaneous Estimation of Lamivudine and Isoniazid

A new UV spectrophotometric absorption ratio method was developed and validated for the simultaneous estimation of lamivudine and isoniazid. The method involved Q-absorption ratio analysis using two wavelengths, with one being the λmax of lamivudine (272 nm, λ2) and the other being the isoabsorptive point of both drugs (246 nm, λ1). Beer’s law was obeyed in the concentration range between 5 and 30 µg/mL for both lamivudine and isoniazid. The results of analysis have been validated statistically and by recovery studies as per ICH guidelines. The accuracy ranged between 99.65 and 101.91% and Sandell’s sensitivity ranged between 0.0229 and 0.0347 µg/cm2. The method was found to be simple, precise, reproducible, rapid, and economical. Hence, it could be used in the analysis of laboratory samples and marketed formulations containing these two drugs in the future.

Sequential Spectrophotometric Method for the Simultaneous Determination of Amlodipine, Valsartan, and Hydrochlorothiazide in Coformulated Tablets

A new, simple and specific spectrophotometric method was developed and validated in accordance with ICH guidelines for the simultaneous estimation of Amlodipine (AML), Valsartan (VAL), and Hydrochlorothiazide (HCT) in their ternary mixture. In this method three techniques were used, namely, direct spectrophotometry, ratio subtraction, and isoabsorptive point. Amlodipine (AML) was first determined by direct spectrophotometry and then ratio subtraction was applied to remove the AML spectrum from the mixture spectrum. Hydrochlorothiazide (HCT) could then be determined directly without interference from Valsartan (VAL) which could be determined using the isoabsorptive point theory. The calibration curve is linear over the concentration ranges of 4–32, 4–44 and 6–20 μg/mL for AML, VAL, and HCT, respectively. This method was tested by analyzing synthetic mixtures of the above drugs and was successfully applied to commercial pharmaceutical preparation of the drugs, where the standard deviation is <2 in the assay of raw materials and tablets. The method was validated according to the ICH guidelines and accuracy, precision, repeatability, and robustness were found to be within the acceptable limits.

Development and Validation of UV-Visible Spectrophotometric Method for Simultaneous Determination of Eperisone and Paracetamol in Solid Dosage Form.

Eperisone Hydrochloride (EPE) is a potent new generation antispasmodic drug which is used in the treatment of moderate to severe pain in combination with Paracetamol (PAR). Both drugs are available in tablet dosage form in combination with a dose of 50 mg for EPE and 325 mg PAR respectively. The method is based upon Q-absorption ratio method for the simultaneous determination of the EPE and PAR. Absorption ratio method is used for the ratio of the absorption at two selected wavelength one of which is the iso-absorptive point and other being the λmax of one of the two components. EPE and PAR shows their iso-absorptive point at 260 nm in methanol, the second wavelength used is 249 nm which is the λmax of PAR in methanol. The linearity was obtained in the concentration range of 5-25 μg/mL for EPE and 2-10 μg/mL for PAR. The proposed method was effectively applied to tablet dosage form for estimation of both drugs. The accuracy and reproducibility results are close to 100% with 2% RSD. RESULTS of the analysis were validated statistically and found to be satisfactory. The results of proposed method have been validated as per ICH guidelines. A simple, precise and economical spectrophotometric method has been developed for the estimation of EPE and PAR in pharmaceutical formulation.

Stability indicating spectrophotometric methods for determination of bumadizone in the presence of its alkaline degradation product

ObjectivesSimple, selective and precise stability indicating spectrophotometric methods were adopted and validated for the quantitative determination of Bumadizone calcium semihydrate (BUM) in presence of its alkaline degradation product (DEG I). MethodsMethod A is based on the application of first derivative (1D) spectrophotometry, then measuring the amplitude of BUM at 245.4 nm. Method B depends on measuring the peak amplitude of the first derivative of the ratio spectra (1DD) at 242.6, 260 and 274 nm over a concentration range of 6–20 μg mL−1. Method C is isoabsorptive point spectrophotometry where total concentration of BUM and DEG I was calculated at their isoabsorptive point at 242.2 nm (Aiso) while DEG I concentration alone can be determined at λmax 320 nm, and then BUM concentration can be determined by subtraction. In Method D ratio subtraction spectrophotometry is applied. ResultsThe four methods were found to be specific for determination BUM in presence of different concentrations of DEG I and were successfully applied for the determination of BUM in Octomotol® tablets. ConclusionStatistical comparison between the results obtained by applying the proposed methods and that obtained by the manufacturer one for the determination of the drug was done, and it was found that there is no significant difference between them.

Spectrophotometric Methods for Simultaneous Determination of Two Hypouricemic Drugs in their Combined Dosage Form

Four simple, precise and accurate spectrophotometric methods have been developed for simultaneous determination of Allopurinol (ALP) and Benzbromarone (BENZ) in their bulk powder and pharmaceutical dosage form. Method (I) is dual wavelength analysis, method (II) is Q-analysis (graphical absorbance ratio) method, method (III) is the mean centering of ratio spectrophotometric (MCR) method while method (IV) is the extended ratio subtraction method (EXRSM). In method (I) two wavelengths were selected for each drug in such a way that the difference in absorbance was zero for the second drug. At wavelengths 238.2 and 261.2 nm ALP had equal absorbance values; therefore, these two wavelengths have been used to determine BENZ; on a similar basis 253 and 274.4 nm were selected to determine ALP. Method (II) involves the formation of Q-absorbance equation using the respective absorptivity values at 245.8 nm (isoabsorptive point) and 250 nm (λmax of ALP). In method (III) the absorption spectra of both ALP and BENZ with different concentrations were recorded over 210-280 and 210-275 nm, respectively, divided by the spectrum of suitable divisor of both ALP and BENZ and then they obtained ratio spectra were mean centered. Method (IV) starts with the normal ratio subtraction method (RSM) for determination of ALP at its λmax (250 nm), while an extension of the already developed method has been established as a new approach for BENZ determination at its λmax (238 nm). Accuracy, precision and recovery studies of the developed methods have been carried out in order to confirm their accuracy. Specificity of the methods was also tested by their application for determination of different synthetic mixtures and they have been successfully used for drugs determination in their combined dosage form. Statistical comparison of the developed methods with the reported HPLC one showed no significant difference.

Development and validation of UV spectroscopic methods for simultaneous estimation of ciprofloxacin and tinidazole in tablet formulation

Two simple, accurate, precise, reproducible and economical UV spectroscopic methods (A & B) for simultaneous estimation of Ciprofloxacin and Tinidazole in tablet dosage form have been developed. Method A employs solving of simultaneous equations based on the measurement of absorbance at two wavelengths, 271nm and 318nm which are the ?max values of Ciprofloxacin and Tinidazole respectively in phosphate buffer (pH 6.8). Method B is based on the principle of Q-Analysis where in the absorbance was measured at 292nm (iso-absorptive point) and 271nm (?max of Ciprofloxacin)in phosphate buffer (pH 6.8). Ciprofloxacin and Tinidazole shows linearity at all the selected wave-lengths and obeys Beer’s law in the concentration range of 10-35µg/mL and 10-80µg/mL respectively. Recovery studies for Ciprofloxacin and Tinidazole were performed and the percentage recovery for both the drugs was obtained in the range of 98.1-99.7% (Method A) and 98.0-100.4% (Method B) confirming the accuracy of the proposed method. Both the methods showed good reproducibility and recovery with %RSD less than 2. Statistical validation of the data shows that the proposed methods can be successfully applied for the routine analysis of drugs in commercial tablets.DOI: http://dx.doi.org/10.3329/icpj.v1i10.11849 International Current Pharmaceutical Journal 2012, 1(10): 317-321

Q-Absorbance Ratio Spectrophotometric Method for the Simultaneous Estimation of Prednisolone and 5-Amino Salicylic Acid in Tablet Dosage form

The present work carries an analytical method development of prednisolone and 5amino salicylic acid in tablet dosage form. The method is based upon Q – absorption ratio method for the simultaneous determination of the prednisolone and 5-amino salicylic acid. Both the drugs are widely used for bacterial cure and are recommended for the patients with mild to moderate inflammation of the digestive tract. Ulcerative colitis and crohn’s disease are the target disorders which are treated by both drug candidates. Absorption ratio method is used for the ratio of the absorption at two selected wavelength one of which is the iso-absorptive point and other being the λmax of one of the two components. Prednisolone and 5-ASA shows their iso-absorptive point at 283 nm in ethanol and 0.1N HCl respectively. The second wavelength used is 302 nm which is the λmax of 5-ASA in 0.1N HCl. The linearity was obtained in the concentration range of 1-10 µg/ml for prednisolone and 5-ASA. This method was applied to all pharmaceutical dosage form because there is no excipients interference between them. The results have been validated by recovery studies.

Combining the isoabsorptive point in the ratio spectrum and the smart ratio difference methods for a single step determination of compounds with overlapped spectra

A new method significantly advantageous over the conventional spectrophotometric methods regarding simplicity, minimal data processing and applicability was developed. The new method is based on the fact that isoabsorptive points whenever present in an absorption spectrum will be retained even after division by a one component as a divisor in the ratio spectrum, in addition to a smart modification of the conventional ratio derivative and ratio subtraction methods. This modified method though simpler, enabled wider range of applications. The proposed method was applied for the analysis of brimonidine and timolol in laboratory prepared mixtures with mean percentage recoveries 100.64±1.10 and 100.96±1.16, respectively, and in their pharmaceutical formulation with mean percentage recoveries 100.88±0.34 and 100.84±0.72, respectively. The suggested method was validated according to USP guidelines and can be applied for routine analysis in quality control laboratories.

Q-Absorbance Ratio Spectrophotometric Method for the Simultaneous Estimation of Rifampicin and Piperine in their Combined Capsule Dosage

The present manuscript describe simple, sensitive, rapid, accurate, precise and economical Q-absorbance ratio method for the simultaneous determination of Rifampicin and Piperine in combined capsule dosage form. Absorbance ratio method uses the ratio of absorbances at two selected wavelengths, one which is an isoabsorptive point and other being the λ-max of one of the two components. Rifampicin and Piperine show an isoabsorptive point at 387 nm in methanol. The second wavelength used is 337 nm, which is the λ-max of Piperine in methanol. The linearity was obtained in the concentration range of 5-40 μg/ml for Rifampicin and 2-20 μg/ml for Piperine. The concentrations of the drugs were determined by using ratio of absorbances at isoabsorptive point and at the λ-max of Rifampicin. The method was successfully applied to pharmaceutical dosage form because no interference from the capsule excipients was found. The results of analysis have been validated statistically and by recovery studies.

SIMULTANEOUS ESTIMATION OF SIMVASTATIN AND SITAGLIPTIN BY USING DIFFERENT ANALYTICAL METHODS

Simple accurate and precise Spectrophotometric methods have been developed for simultaneous estimation of Simvastatin (SIM) and Sitagliptin (SITA) by employing three methods. Method A was simultaneous equation method; the method involves formation and solving the simultaneous equation using 238 nm and 267 nm as two wavelengths for SIM and SITA respectively. Method B was first order derivative spectrophotometry. The first order derivative absorption at 230 nm (zero crossing point of SITA) was used for SIM and 275nm (zero crossing point of SIM) was used for SITA. Method C involved Q-absorption analysis based on the measurement of absorbance at two wave lengths that is the λmax of SITA 267 nm and isoabsorptive point of both drugs at 250 nm. The three methods obeyed the Beer law in the concentration range of 3-15

Stability indicating HPLC and spectrophotometric methods for the determination of bupropion hydrochloride in the presence of its alkaline degradates and related impurity

Four sensitive and selective stability-indicating methods for the determination of bupropion hydrochloride in the presence of its alkaline degradates, related impurity, 3-chlorobenzoic acid, and in its pharmaceutical formulation were developed. Method A is an isocratic reversed phase HPLC, good separation between bupropion hydrochloride, its alkaline degradates and related impurity was achieved using a mobile phase of 1.2% w/v ammonium dihydrogen phosphate pH 4.5 and acetonitrile (80:20, v/v) and detection at 210nm. Method B is based on the first derivative (D1) measurement of the drug at 259nm, zero contribution point of its alkaline degradates and related impurity. Method C is based on the resolution of the drug, its alkaline degradates and related impurity by first derivative ratio spectra (DD1). Method D is based on the determination of bupropion hydrochloride and its impurity by the Q value method at 248nm, 227nm and at isoabsorptive point 237nm. These methods are successfully applied for the determination of bupropion hydrochloride in bulk powder, pharmaceutical formulation and in the presence of its alkaline degradates and related impurity. The results obtained are statistically analyzed and there are no significant differences between the four methods and the official one with respect to accuracy and precision.

Development and Validation of Analytical Method for Simultaneous Estimation of Diclofenac Sodium and Ofloxacin in Bulk and Ophthalmic Formulations using UV–Visible Spectrometry

Two simple, accurate, precise, reproducible, requiring no prior separation and economical procedures for simultaneous estimation of diclofenac sodium and ofloxacin in bulk and ophthalmic formulations have been developed. The first method employs formation and solving of simultaneous equations using 273 nm and 291 nm as two analytical wavelengths for both drugs in acidic methanol. The second method is the Q value analysis based on measurements of absorptivity at 263 nm (as an iso-absorptive point) and 273 nm. Diclofenac sodium and ofloxacin at their respective λmax 273 nm and 291 nm and at isoabsorptive point 263 nm show linearity in a concentration range of 1-20 µg/ml. Recovery studies range from 99.67% for diclofenac sodium and 100.35% for ofloxacin in case of simultaneous equation method and 99.99% for diclofenac sodium and 100.07% for ofloxacin in the case of Q - analysis method confirming the accuracy of the proposed method. In conclusion, the proposed method is recommended for routine analysis since it is rapid, simple, accurate and also sensitive and specific

Spectrophotometric methods for simultaneous determination of Carvedilol and Hydrochlorothiazide in combined dosage form

Two simple, precise, rapid and economic spectrophotometric methods have been developed for simultaneous determination of Carvedilol (CV) and Hydrochlorothiazide (HCT) in bulk powder and combined dosage form. Method (I) is based on dual wavelength analysis while Method (II) depends on UV-spectrophotometric determination using Q-analysis (graphical absorbance ratio) method.In Method (I), two wavelengths were selected for each drug in such a way that the difference in absorbance is zero for the second drug. At wavelengths 238 and 248.8nm HCT has equal absorbance values, therefore, these two wavelengths have been used to determine CV, on similar basis 266 and 289.4nm were selected to determine HCT in the combined formulation. Method (II) involves the formation of Q-absorbance equation using the respective absorptivity values at 229.2nm (isoabsorptive point) and 241nm (λmax of CV). The drugs obey Beer’s Lambert’s law in the concentration range of 1–10μg/mL for both CV and HCT (for Method I) and in the range of 1–10 and 2–10μg/mL for CV and HCT, respectively (for Method II). The accuracy and precision were determined and recovery studies confirmed the accuracy of the developed methods that were carried out following the International Conference on Harmonization (ICH) guidelines. Statistical comparison of the suggested methods with the reported spectrophotometric one using F and t tests showed no significant difference regarding both accuracy and precision.