Absorbance Subtraction Research Articles

Ecofriendly spectrophotometric methods for simultaneous determination of remdesivir and moxifloxacin hydrochloride as co administered drugs in corona virus treatment

Remdesivir and moxifloxacin hydrochloride are among the most frequently co-administered drugs used for COVID-19 treatment. The current work aims to evaluate green spectrophotometric methodologies for estimating remdesivir and moxifloxacin hydrochloride in different matrices for the first time. The proposed approaches were absorbance subtraction, extended ratio subtraction and amplitude modulation methods. In order to determine the absorbance of the investigated medications in combination at the isoabsorptive point, the pure moxifloxacin hydrochloride absorbance factor is applied using the absorbance subtraction method, which modifies the zero absorption spectra of the drugs under investigation at the isoabsorptive point (229 nm). The spectrum of moxifloxacin hydrochloride is more extended in the plateau area between 340 and 400 nm, where remdesivir exhibits no absorption. So, also, the ratio spectra were successfully manipulated for quantification of the two drugs. Regarding the pharmacokinetic profile of remdesivir (Cmax 4420 ng/mL) and moxifloxacin hydrochloride (Cmax 3.56 µg/mL), the proposed methods were effectively used to spectrophotometrically determine remdesivir and moxifloxacin hydrochloride in plasma matrix. The new approach was validated using the ICH guidelines for specificity, linearity, precision, and accuracy. The greenness of the reported methodologies was evaluated using two metrics: the analytical eco-scale and the green analytical procedure index.

Spectral resolution techniques for the simultaneous spectrophotometric determination of anti-Parkinson drugs in their combined pharmaceutical dosage form and biological sample based on multivariate calibration and absorbance subtraction methods

In this study, simultaneous determination of levodopa (LEV) and carbidopa (CBD) in binary mixtures, pharmaceutical formulation, and biological sample was conducted using the application of simple, fast, sensitive, and accurate UV-spectrophotometry in combination with chemometrics methods. The first method is net analyte signal (NAS) based on the multivariate calibration methods. The limit of detection (LOD) and limit of quantification (LOQ) were 0.9758, 0.7633 µg/mL and 2.956, 2.313 µg/mL over the linear range of 5–40 and 0.5–20 µg/mL for LEV and CBD, respectively. In the NAS approach, the mean recovery values of mixtures were 100.12 % for LEV and 99.65 % for CBD, where root mean square error (RMSE) values were 0.0106 and 0.0141 for LEV and CBD, respectively. The second method is absorbance subtraction (AS) based on the absorption factor technique for analyzing the isosbestic point. This model was constructed at an isosbestic point of 261 nm in the range of 5–40 and 0.5–20 µg/mL with coefficient determination (R2) of 0.9985 and 0.9996 for LEV and CBD, respectively. AS method could estimate LEV and CBD with LOD values of 1.924 and 0.5657 μg/mL and LOQ values of 5.833 and 1.714 μg/mL, respectively. The recovery percentage was between 91.50 % to 104.60 % with RMSE of 0.1455 for LEV and 92.00 % to 106.66 % with RMSE of 0.2508 for CBD. The introduced approaches have the benefit of concurrent analysis of the mentioned components without any pretreatment. Statistical comparison of the results of real sample analysis with high-performance liquid chromatography (HPLC) did not show a significant difference. These methods can replace HPLC in quality control laboratories when fast, precise, and low-cost analysis is needed.

Utilization of absorbance subtraction and ratio difference green spectrophotometric methods for the quantification of alfuzosin hydrochloride and tadalafil in their binary mixture

Alfuzosin hydrochloride and tadalafil fixed-dose combination tablets were recently formulated for the treatment of individuals with lower urinary tract symptoms caused by benign prostatic hyperplasia. Herein, the first spectrophotometric methods for quantitative analysis of alfuzosin hydrochloride and tadalafil in their binary mixture were established. The spectral overlapping of alfuzosin hydrochloride and tadalafil made direct simultaneous analysis unfeasible. Therefore, two mathematical methods were used to solve these overlapping spectra: absorbance subtraction and ratio difference. The absorbance subtraction method manipulates the zero absorption spectra of the studied drugs at the isoabsorptive point (272 nm) and uses the absorbance factor of pure ALF to calculate the absorbance of the studied drugs in the mixture at the isoabsorptive point. The ratio spectra method, on the other hand, manipulates the ratio spectra of the studied drugs, which are obtained by dividing each drug’s zero absorption spectra by a divisor spectrum from the second drug. The ratio amplitude difference between 251 nm and 211 nm was directly proportional to alfuzosin hydrochloride, whereas between 292 nm and 222 nm it was directly proportional to tadalafil. The methods used were verified in accordance with the recommendations of the ICH and demonstrated adequate linear regression in working ranges of 1–15 µg/mL for alfuzosin hydrochloride and 3–40 µg/mL for tadalafil. The methods were accurate, precise, and selectively employed to quantify alfuzosin hydrochloride and tadalafil in their combined tablets.

Novel UV Spectrophotometric approaches for the concurrent determination of Teneligliptin and Metformin in Tablet Formulation

In the study simultaneous assessment of teneligliptin hydrobromide hydrate and metformin hydrochloride in tablets were developed and validated by four new UV spectroscopic approaches. The ratio difference approach was used to measure the variation in two selected amplitudes of ratio spectra, and the regression equation was employed to determine the amounts of pharmaceuticals. The second approach, known as the first derivative of ratio spectra approach, the UV spectra were transformed into their ratio spectra and corresponding first derivatives, and the first-derivative signal was gauged at 275 and 226.2 nm for metformin hydrochloride and teneligliptin hydrobromide hydrate, sequentially, making use of 2 nm as the wavelength interval (Δλ) and a factor of 1 as a scaling factor, respectively. Whereas absorbance subtraction method works with the principle of finding isosbestic point and calculating absorption factor. The fourth approach, known as the dual wavelength method, relies on computing the absorbance difference at two different wavelengths where the other drug has same absorbance. Linearity and range, specificity, accuracy, precision, limit of detection and quantification were among the criteria evaluated during validation of the new methods in agreement with ICH recommendations and found to be within the permitted limits. For both the medicines, a linear response was observed in all four methods over the concentration sequence of 2-12 µg/ml. Therefore, the proposed methodologies may be successfully used for the concurrent evaluation of teneligliptin hydrobromide hydrate and metformin hydrochloride in tablet form.

Absorbance Subtraction Method for the Determination of Losartan Potassium and Hydrochlorothiazide in Bulk and Tablets

A simple, accurate and precise method was proposed for the determination of losartan potassium and hydrochlorothiazide. The overlain spectra of losartan potassium and hydrochlorothiazide were found to have an isoabsorptive point at 266.9nm, while the spectrum of later is extended with an absorption maximum at 325 nm; where the former is not interfering, based on these spectral characteristics, simultaneous spectrophotometric determination of the two analytes in combined dosage was possible using absorbance subtraction method. The method showed good precision in term of repeatability and intermediate precision with relative standard deviations were less than 2% in both cases. The method’s accuracy was confirmed by the close agreement between the theoretical and actual concentrations of the analytes in nine laboratory prepared synthetic mixtures. The proposed method was successfully applied to the analysis of a commercial product, the assay results were 102.60% and 99.88%with %RSD 1.68 and 1.68for LSP and HCT, respectively.

Different methods for resolving overlapping UV spectra of combination medicinal dose forms of ciprofloxacin and metronidazole

Four simple, specific, easy, precise and accurate spectrophotometric methods were developed for the first time to examine ciprofloxacin and metronidazole in combination, without having been separated beforehand by the developed methods. Ciprofloxacin and metronidazole were determined by utilizing advanced absorbance subtraction (AAS), spectrum subtraction, bivariate and ratio difference methods. Precision, repeatability, robustness, and accuracy were all determined to be within acceptable levels after each of these procedures underwent validation in accordance with ICH recommendations. Each method’s benefits and drawbacks are illustrated, and the proposed and reported methodologies were statistically compared.

A sustainable data processing approach using ultraviolet-spectroscopy as a powerful spectral resolution tool for simultaneously estimating newly approved eye solution in the presence of extremely carcinogenic impurity aided with various greenness and whiteness assessment perspectives: Application to aqueous humor

Drug impurities are now seen as a major threat to drug safety around the world, especially when it comes to carcinogenic impurities. Here, we present the first spectrophotometric approach for the quantification of lignocaine and fluorescein in the presence of 2,6-xylidine, lignocaine’s carcinogenic impurity. The approach depends on overcoming unresolved bands through a data processing strategy employing 10 affordable, simple, and sensitive spectrophotometric methods. Fluorescein analysis (1–16 μg mL−1) was performed using direct ultraviolet spectrophotometry (D0) at 478 nm; then, the ratio subtraction method allowed the removal of interference caused by the fluorescein spectrum. From the resulting ratio spectra, 2,6-xylidine (40–160 μg mL−1) can be efficiently determined at 280 nm. However, lignocaine (72–320 μg mL−1) was analyzed using different ultraviolet-based methods, including continuous wavelet transform, ratio derivative by Savitzky–Golay filters, mean centering, second derivative of ratio spectra, ratio spectra difference spectrophotometry, extended ratio subtraction, absorbance subtraction, Q-absorbance ratio, and area under the curve. In line with International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH), the presented approach was evaluated by its coefficients of determination, detection limits, quantification limits, and relative standard deviations. Similarly, the developed approach was assessed for whiteness, greenness, and sustainability using five assessment tools, including National Environmental Method Index, Eco-Scale Assessment, Complementary Green Analytical Procedure Index, Analytical Greenness Metric, and RGB12, offering promising results. Owing to the satisfactory analytical performance, besides the sustainability, affordability, simplicity, and cost efficiency of the presented methods, their application for quality control and in situ analysis in minimal-infrastructure laboratories increases, increasing the surveillance potential.

FLUOKSETİN VE OLANZAPİNİN EŞ ZAMANLI SPEKTROFOTMETRİK TAYİNİ VE YEŞİL KİMYA UYGULAMALARI

Objective: In our study, the simultaneous determination of fluoxetine (FLX) and olanzapine (OLZ) was performed by absorbance subtraction and absorbance correction spectrophotometric methods. Material and Method: The active substances were determined by choosing the isosbestic point of 232 nm in the absorbance subtraction method and 255 nm and 245 nm wavelengths in the absorbance correction method. The accuracy of the methods was determined by applying the percentage recovery studies to the laboratory mixtures. The percent recovery values were found in the range of 98.1-100.2 for OLZ and 96.8-105.3 for FLX. The concentration range studied was 3.12-15.62 and 3.45-17.28 µg/ml for OLZ and FLX, respectively. Result and Discussion: In the study, two active substances used in antidepressant treatment were determined simultaneously. Today, these active substances used in the treatment have started to be used in combination in order to achieve a better effect of the treatment. Therefore, simultaneous analysis of two active substances becomes important. Two different spectrophotometric methods were used for analysis. The methods have been successfully applied and validated for the simultaneous determination of antidepressant active substances. Since the applied methods do not require pre-separation and can be applied directly, the amount of waste generated is reduced. Environmentally sensitive methods have been applied.

Development and Validation of UV-Spectroscopic Method for Simultaneous Estimation of Metformin Hydrochloride and Pravastatin Sodium

Introduction: A new, simple, precise, accurate, and reproducible method was developed and validated for the simultaneous estimation of Metformin Hydrochloride (MH) and Pravastatin Sodium (PS) in pure form.
 Methodology: Simultaneous estimation of Metformin Hydrochloride (MH) and Pravastatin Sodium (PS) was estimated by ultraviolet (UV) spectrophotometry using the absorbance subtraction method. The method was based on the measurement of absorbance at two wavelengths 232 nm and 238 nm, of metformin and Pravastatin Sodium respectively. These studies were performed at three different levels (75%, 100%, and 125%) and the % recovery of MH and PS was calculated.
 Results: The LOD and LOQ were found to be 0.481 μg/ml and 0.670μg/ml for MH and 1.15μg/ml and 1.68μg/ml for PS respectively. All the statically analyses were within the standard limits. It proves that the method was repeatable and selective for the simultaneous.
 Conclusion: Therefore, the present study concludes that it can be successfully used for simultaneous estimation of MH and PS in pure and pharmaceutical dosage forms. The developed method was found to be simple, precise, and accurate.

A green spectrophotometric method for the simultaneous determination of nasal binary mixture used in respiratory diseases: Applying isosbestic point and chemometric approaches as a resolving tool, greenness evaluation

Nasal drug combination is a very useful therapy for elevating the symptoms of various respiratory diseases as seasonal allergic rhinitis and infectious respiratory illness as pandemic COVID-19. One of best combination is Fluticasone propionate (FLU) and Azelastine (AZE). In this study, different UV spectrophotometric and chemometric methods have been applied for quantitative analysis of FLU and AZE without previous separation in their pure form, laboratory prepared mixture and pharmaceutical dosage form. Absorbance subtraction (AS) and Amplitude modulation (AM) spectrophotometric methods have been applied for the simultaneous determination of the cited drugs. Besides, three well-known chemometric techniques; namely, classical least squares (CLS), partial least square (PLS), and principal component regression (PCR) have been applied for the simultaneous analysis of both drugs by using spectrophotometric data. To be friendly to the environment, the greenness of the proposed methods was taken into consideration and evaluation of the analytical methods’ greenness was done using two green analytical chemistry metrics known as, Analytical Greenness Calculator and an eco-scale scoring method. They indicated that the methods were environmentally friendly in relation to numerous approaches like instrument, reagents, and safety of waste. Analyzing laboratory prepared mixtures including different quantities of FLU and AZE, as well as their marketed dose form, was used to assess the selectivity of the applied methods. The validity of the developed methods was investigated by applying the standard addition technique. The resulting data were statistically compared to those obtained by the official or reported HPLC methods for FLU and AZE, which revealed no significant difference in accuracy and precision at p = 0.05.

RETRACTED: Simultaneous determination of hydrochlorothiazide, amlodipine, and telmisartan with spectrophotometric and HPLC green chemistry applications

For the quantifiable amounts of Telmisartan (TLM) and Hydrochlorothiazide (HYD) in the presence of Amlodipine (AML) in a ternary mixture of synthetic laboratory mixture, a novel, sensitive, quick, and practical reversed-phase high-performance liquid chromatography (RP-HPLC) method was given. In order to separate, a Waters Spherisorb ODS-2 C18 column was used. For HYD, TLM, and AML, these techniques were viable over linearity ranges of 4-12μg/mL, 4-25μg/mL, and 5-40μg/mL, respectively. The mobile phase system was acetonitrile:methanol: phosphate buffer at pH 2.5 (65:5:30 v/v/v), and the flow rate was 1.5mL/min. Novel spectrophotometric methods were applied for active substances to determine simultaneously. The first method is absorptivity centering using factorized spectrum, and the second method is dual amplitude difference coupled with absorbance subtraction. These approaches have been effectively applied to bulk, laboratory synthetic mixtures to employ active components quantitatively. Correlation coefficients were found to be higher than 0.99 and the limit of detection values lower than 0.49μg/mL in both spectrophotometric methods. The methodologies were validated following ICH recommendations. In the developed HPLC method, the limit of detection values was found to be 0.01μg/mL for HYD and 0.02μg/mL for AML and TLM. The correlation coefficients for the HPLC method were found to be 0.9971 for HYD, 0.9990 for AML, and 0.9983 for TLM. The suggested HPLC technique is a simple, effective, sensitive, environmentally friendly, and time-saving approach for determining TLM and HYD in the presence of AML.

Smart Eco-Friendly Spectrophotometric Methods Resolving Highly Overlapping Spectra: Application to Veterinary Antibiotic Injections.

Over the last few years, mathematical manipulation has proved to be a very powerful means of successfully resolving severely overlapped spectra for various multicomponent mixtures. Smart and environmentally friendly spectrophotometric determination approaches were used for two binary mixtures of fixed dose veterinary injections containing flunixin meglumine (FLU) combined with either florfenicol (FLR), or oxytetracycline HCl (OXY). Regarding the first mixture, both FLU and FLR were determined by three successive resolution techniques, which were; constant multiplication coupled with spectrum subtraction (CM-SS), derivative ratio (DD1), and ratio difference (RD), and two progressive resolution techniques which were absorbance subtraction (AS) and amplitude modulation (AM). Also, graphical representation of concentration of the two drugs through concentration value (CNV) method was also applied. Concerning the second mixture, both FLU and OXY showed severely overlapped spectra and a comparative study was conducted for the determination of each drug by constant center (CC), ratio subtraction via amplitude difference coupled with spectrum subtraction (RS/AD-SS), constant value via amplitude difference (CV-AD), and advanced concentration value (ACV) methods. Calibration graphs of the first mixture were linear over the range 5-40 µg/mL for FLU, and 3-40 µg/mL for FLR. The proposed methods overcame the problem of the overlapped spectra and the presence of a minor component in the mixture. Regarding the second mixture, calibration graphs were linear over the range 2.5-24 µg/mL for FLU and 4-28 µg/mL for OXY. The proposed methods were successfully validated as per International Council for Harmonization (ICH) guidelines. The obtained results were statistically compared with the official or reported methods, showing no significant difference concerning accuracy and precision. The methods were evaluated for greenness by three different assessment tools: NEMI, analytical ecoscale, and GAPI. The methods were successfully applied for the simultaneous determination of the two combinations in synthetic mixtures and their marketed antibiotic veterinary injections: Megluflor® and Floxon®.

Fingerprinting and iso-absorptive resolution techniques for the spectrally overlapping Dutasteride and Silodosin mixture: Content uniformity testing along with greenness profile assessment

The realm of spectrophotometric analysis has witnessed a remarkable progress in inventing faster and simpler resolution techniques for spectrally overlapping drug mixtures. Eco-friendly and progressive spectrophotometric methods were firstly developed in this work, for the simultaneous determination of Dutasteride (DUT) and Silodosin (SLD) in their newly-marketed dosage form. The proposed methods focused on the unique spectral features of this mixture including spectral extension of SLD over DUT spectrum as well as existence of iso-absorptive points. By such way, the methods were classified into two categories; the first one was “fingerprint resolution techniques” including constant extraction coupled with spectrum subtraction and ratio subtraction coupled with constant multiplication methods. The former represented a new modification to the classical constant extraction method where one divisor and lower steps were manipulated instead. The second category was “iso-absorptive resolution techniques”, such as absorptivity centering, absorbance subtraction and amplitude modulation methods. Different solvents were investigated where ethanol was found to be the optimum one regarding drugs solubility, signal sensitivity and environmental, health & safety (EHS) score. Validity of the suggested methods was assessed as per ICH-guidelines and found to be linear over concentration ranges of 5.0–90.0 µg/mL for DUT and 5.0–120.0 µg/mL for SLD. The methods were successfully applied for quantifying the cited drugs in their combined dosage form and evaluating their content uniformity. Moreover, the insignificant statistical difference between the proposed methods and official HPLC ones encourages the utilization of such spectrophotometric methods as greener and faster candidates, especially in modest quality control laboratories. Methods’ greenness profile was finally guaranteed through several assessment tools, namely; national environmental methods index (NEMI), analytical eco-scale, green analytical procedure index (GAPI) and analytical greenness (AGREE) metric.

Smart Spectrophotometric Methods for Concurrent Determination of Furosemide and Spironolactone Mixture in Their Pharmaceutical Dosage Forms

Simple, precise, accurate and specific spectrophotometric methods are progressed and validated for concurrent analysis of Furosemide (FUR) and Spironolactone (SPR) in their combined dosage form depend on spectral analysis procedures. Furosemide (FUR) in the binary mixture could be analyzed at its λmax 274 nm using its recovered zero order absorption spectrum using constant multiplication method (CM). Spironolactone (SPR) in the mixture could be analyzed at its λmax 238 nm by ratio subtraction method (RS). Concurrent determination for FUR and SPR in their mixture could be applied by amplitude modulation method (AM), absorbance subtraction method (AS) and ratio difference (RD). Linearity ranges of FUR and SPR were (2.0µg/mL-22.0 µg/mL) and (3.0µg/mL-30.0 µg/mL), respectively. Specificity of the proposed spectrophotometric methods was examined by analyzing the prepared mixtures in laboratory and was applied successfully for pharmaceutical dosage form analysis which have the cited drugs without additives contribution. The proposed spectrophotometric methods were also validated as per as the guidelines of ICH. Statistical comparison was performed between the obtained results with those from the official methods of the cited drugs, using one-way ANOVA, F-test and student t-test. The results are exhibiting insignificant difference concerning precision and accuracy.

New microfluidic paper-based analytical device for iron determination in urine samples.

Iron is an important micronutrient involved in several mechanisms in the human body and can be an important biomarker. In this work, a simple and disposable microfluidic paper-based analytical device (µPAD) was developed for the quantification of iron in urine samples. The detection was based on the colorimetric reaction between iron(II) and bathophenanthroline and the reduction of iron(III) to iron(II) with hydroxylamine. The developed µPAD enabled iron determination in the range 0.07-1.2mg/L, with a limit of detection of 20µg/L and a limit of quantification of 65µg/L, thus suitable for the expected values in human urine. Additionally, targeting urine samples, the potential interference of the samples color was overcome by incorporating a sample blank assessment for absorbance subtraction. Stability studies revealed that the device was stable for 15days prior to usage and that the formed colored product was stable for scanning up to 3h. The accuracy of the developed device was established by analyzing urine samples (#26) with the developed µPAD and with the atomic absorption spectrometry method; the relative deviation between the two sets of results was below 9.5%.

Different spectrophotometric methods manipulating ratio spectra for the assay of hydrocortisone acetate and clioquinol in their topical preparation

Simple and precise spectrophotometric methods for quantitative assay of a mixture of hydrocortisone acetate (HCA) and clioquinol (CL) were developed and validated through different mathematical manipulation pathways. The developed methods utilized ratio spectra for resolving binary mixtures including absorbance subtraction, ratio subtraction coupled with spectrum subtraction, constant multiplication, constant value, and derivative ratio. The proposed methods were proved to be specific by analysing the laboratory-prepared mixtures and were applied for the assay of topical preparation successfully. The methods were validated using ICH guidelines where accuracy, repeatability and intermediate precision were within the acceptable limits. The linearity range was found to be 2-22 for HCA and 1.5-7 µg/mL for CL in all proposed methods and 2-7 µg/mL for HCA and CL in absorbance subtraction method through using a unified regression equation. The findings were statistically evaluated with respect to the official and reported methods, demonstrating that there was no significant difference.

Earth friendly spectrophotometric methods based on different manipulation approaches for simultaneous determination of aspirin and omeprazole in binary mixture and pharmaceutical dosage form: Comparative statistical study

Aspirin and omeprazole combining has proven their effectiveness clinically in the treatment and prevention of cardiovascular diseases in patient with gastric diseases and gastric ulcers. Simultaneous determination of omeprazole and aspirin in their combination is a challenge due to the overlapping spectra of these drugs. Six smart and different spectrophotometric methods were developed for the analysis of omeprazole and aspirin in binary mixture and pharmaceutical dosage form. These smart methods characterized by simplicity and accuracy. The first two methods based on minimal mathematical data processing based on the zero order absorption spectra were; dual wavelength and advanced absorbance subtraction methods. The third method is first and second derivative spectrophotometric method that based on derivative spectra. The last three methods based on ratio spectra manipulation are named; ratio difference, mean centering and derivative ratio spectrophotometric methods. The linearity range of omeprazole was 2–20 μg/mL for dual wavelength method and 2–30 μg/mL for the other ones, while aspirin showed a good linearity over a range of 2.5–30 μg/mL for all methods. The correlation coefficients were greater than 0.999. The results of the developed methods are statistically compared with each other and with the results of the reported HPLC method showing no significant difference. The greenness of the developed methods was assessed using eco-scale scoring method revealing excellent greenness of the applied methods. This spectrophotometric methods is more sensitive and greener with comparing by the reported one so, these developed methods are considered eco-friendly to the environment.

Smart Spectrophotometric Methods Based on Feasible Mathematical Processing and Classical Chemometry for The Simultaneous Assay of Alcaftadine and Ketorolac in Their Recently Approved Pharmaceutical Formulation.

Alcaftadine (ALC) and Ketorolac tromethamine (KET) binary combination is a new co-formulated pharmaceutical product that is used to treat allergic conjunctivitis. The present work utilizes three simple, precise, accurate, and rapid spectrophotometric and chemometric methods to determine the recently released pharmaceutical formulation. The methods include the first derivative of absorbance spectrum (Method A), dual-wavelength (Method B), and absorbance subtraction methods (Method C). ICH guidelines have been used to validate the developed methods. Linear regression lines were found over the concentration range of 1-9 and 1-12 μg mL-1, 1-8 and 2-10 μg mL-1, and 2-10 and 2-10 μg mL-1 of ALC and KET for methods A, B, and C respectively. All the methods showed correlation coefficients higher than 0.999, in addition to low LOQ and LOD which indicate high sensitivity of the proposed methods.

Development and Validation of Absorbance Subtraction Method for Simultaneous Determination of Atorvastatin Calcium and Sildenafil Using UV Spectrophotometer

Development and Validation of Absorbance Subtraction Method for Simultaneous Determination of Atorvastatin Calcium and Sildenafil Using UV Spectrophotometer

Development and Validation of the UV Spectrophotometric Method for Simultaneous Determination of Paracetamol and Pseudoephedrine in Bulk and Combined Tablet Dosage Form

Paracetamol (PARA) and Pseudoephedrine (PSE) are co-formulated drugs that and widely used over the world for the treatment of symptoms associated with common cold. In the present study a specific, rapid and simple UV spectrophotometric method with good sensitivity was developed and validated for the simultaneous quantification of PARA and PSE in bulk and tablet dosage form using methanol as diluent. This method is based on the direct measurement of absorbance at 248 nm wavelength for PARA solution, whereas dual-wavelength absorption measurement is applied for PSE solution (i.e. subtraction of absorbance at 217 nm from that at 201 nm, in which PARA absorbance subtraction is equal to zero). The calibration curves were linear (R2 = 0.9988 and 0.9976 for PARA and PSE, respectively) in a concentrations range of 2 – 10 μg/mL for both drugs. Limit of detection is LOD = 0.4159 μg/mL and 0.29679 μg/mL and the limit of quantification is LOQ = 1.26 μg/mL and 0.8994 μg/mL for PARA and PSE, respectively. The RSD% values for all levels of precision (repeatability, intra-day and inter-day) are within the specified limit for both drugs. The accuracy of PARA determination was ascertained by standard addition method, and the percentage recovery for 50, 100, and 150 % of standard were 97.93, 100, and 101.39%, respectively (RSD% = 1.7). The accuracy of PSE determination was studied by percentage recovery (n = 3), and the results were 100.7, 101.16, and 99.57% (RSD% = 0.6648). The proposed spectrophotometric method was successfully applied to the analysis of commercial tablets and the obtained results were satisfactory.