Novel two wavelength spectrophotometric methods for simultaneous determination of binary mixtures with severely overlapping spectra

Novel Deliberately Sensitive and Selective Tetrahydrozoline Voltammetric Sensors Integrated with a Copper Oxide Nanoparticle/Zeolite Platform

The present study introduced a novel disposable screen-printed carbon electrodes (SPCEs) modified with copper oxide/zeolite nanostructures for eco-friendly selective differential pulse voltammetric quantification of tetrahydrozoline (THZ) in eyedrop samples and biological fluids. Modification of the electrode matrix with copper oxide nanoparticles/zeolite nanostructures (CuONPs/ZY) with their effective and synergistic electrocatalytic activity enhanced the electrode performance against electrooxidation of THZ at 0.960 V in BR at pH 9.0 with a diffusion-controlled reaction mechanism. The tentative oxidation mechanism based on molecular orbital calculations postulates the oxidation of THZ molecules through oxidation of a nitrogen atom five-membered ring and the participation of two electrons/protons in the electrode reaction. Linear calibration curves were illustrated within a wide THZ concentration range from 0.24 to 57.2 μg mL-1 recording a limit of detection (LOD) value of 0.0799 μg mL-1. The CuONPs/ZY/SPEs exhibited improved performance compared with the sole reported THZ sensor-based gold film-plated carbon paste electrodes, in addition to their high reproducibility of fabrication and measurement and prolonged shelf lifetime. Tetrahydrozoline was successfully assayed in the presence of excipients, degradation products, and chloramphenicol. The presented voltammetric sensor can be considered as an eco-friendly and reliable analytical approach for monitoring THZ residues in eye drop samples and biological fluids with high recovery compared with the official pharmacopeial analytical protocol. The presented sensors were assessed according to an EcoScale tool and also compared with the reported THZ sensor.

State-of-the-art mathematically induced filtration approaches for smart spectrophotometric assessment of silodosin and solifenacin mixture in their new challenging formulation: Multi-tool greenness and whiteness evaluation

Benign prostatic hyperplasia is one of the most predominant health disorders in men with increasing incidence by age and usually accompanied with other bothersome symptoms. A new fixed dose combination, containing Silodosin and Solifenacin, has been recently launched for relieving such disorder associated with overactive bladder syndrome. In the current work, three smart, innovative and white spectrophotometric methods have been newly developed and optimized for simultaneous determination of the studied drugs in their binary mixture using water as an eco-friendly solvent. The adopted strategy relied on calculation of one or two factors as numerical constant or spectrum allowing mathematical filtration of desired analyte and full removal of any overlapped components in the mixture. The developed methods are categorized over two spectrophotometric platform windows. Window I deals with absorption spectra in its native forms (zero-order) including a newly developed method termed induced concentration subtraction (ICS) as well as induced dual wavelength (IDW) methods. Whereas window III is concerned with ratio spectra as in induced amplitude modulation (IAM) method. Compared to classical spectrophotometric methods, the proposed ones are superior in overcoming the inherited challenges in zero-order absorption spectrum of Solifenacin, particularly its very low absorptivity and lack of unique absorption maximum. Validity of the methods were thoroughly assured as per ICH guidelines with unified regression over 3.0-50.0 µg/mL in ICS method while IDW and IAM ones possessed linearity ranges of 3.0-50.0 µg/mL of Silodosin and 5.0-60.0 µg/mL of Solifenacin. The work was also extended to verify content uniformity of dosage units in accordance with USP recommendations. Greenness profile of the proposed methods was clearly assessed, in comparison to the reported analysis ones, via state-of-the-art software metrics, namely, green solvent selection tool (GSST), complementary green analytical procedure index (ComplexGAPI) and analytical greenness (AGREE). Finally, the proposed methods were in good adherence to the recently published postulates of white analytical chemistry.

Eco-friendly simultaneous multi-spectrophotometric estimation of the newly approved drug combination of celecoxib and tramadol hydrochloride tablets in its dosage form

Food and Drug Administration (FDA) recently approved co-formulated celecoxib and tramadol for the treatment of acute pain in adults. Three spectrophotometric methods were efficiently applied to estimate the co-formulated Celecoxib and Tramadol in their tablets; second derivative 2D-spectrophotometry technique (method I), induced dual-wavelength technique (method II) and dual-wavelength resolution technique (method III). The proposed methods were successfully validated following the International Council for Harmonisation (ICH) guidelines and statistically assessed based on the correlation coefficients, relative standard deviations as well as detection and quantitation limits. The obtained results revealed non-significant differences compared to the reported results as revealed by the variance ratio F test and Student t test. Moreover, the applied techniques were further assessed concerning their greenness based on the analytical eco-scale method revealing an excellent green scale with a final score of 95. The proposed spectrophotometric techniques could be applied for the routine analysis and quality control of the studied drugs in their dosage form.

Simultaneous analysis of two drugs used as supportive treatment for COVID-19: comparative statistical studies and analytical ecological appraisal

Pharmaceutical quality control products (QC) demand quick, sensitive, and cost-effective methods to ensure high production at a low cost. Green analytical methods are also becoming more common in pharmaceutical research to cut down on the amount of waste that goes into the environment. Meclizine hydrochloride (MZH) and pyridoxine hydrochloride (PYH) are reported to be excellent for calming down COVID-19. As a result, the amount of MZH and PYH manufactured by multinational pharmaceutical organizations has increased considerably during the last several months. The present work proposes three environmentally friendly, straightforward, and sensitive spectrophotometric procedures for quantification of MZH in the presence of PYH in a pure and marketable formulations. The approaches under examination include ratio subtraction (RSM), induced dual wavelength (IDW), and Fourier self-deconvolution (FSD). PYH, on the other hand, was directly quantified at 290 nm. For both drugs, the procedures follow Beer’s law in the range of (5–50 µg/mL). The RSM, IDW, and FSD methods, as well as the zero-order approach for PYH, have all been verified in accordance with ICH standards. The ecological value of established methodologies was determined using four distinct ways: the national environmental methods index (NEMI), the analytical Eco-scale, the Analytical Greenness Metric (AGREE), and the green analytical process index (GAPI). Comparing the findings to those of the previously described spectrophotometric technique, no major changes were identified.

Sticking - pulling strategy for assessment of combined medicine for management of tough symptoms in COVID-19 Pandemic using different windows of spectrophotometric Platform-Counterfeit products' detection

This study presents a comprehensive comparative study of different green spectrophotometric approaches without any physical separation on processing a ternary mixture of Aceclofenac (ACE), Paracetamol (PAR) and Rabeprazole (RAB) in combined medicine for managing tough symptoms in the COVID-19 Pandemic. The different univariate complementary resolutions according to the response used for the assay of the cited drugs after applying the processing steps were implemented using successive in-silico sample enrichment for resolving the ternary mixture via different windows of spectrophotometric platform using sticking - pulling strategy (SPS). Window I; based on manipulation of the data of zero order absorption spectrum of the mixture using novel Extended absorbance difference (EAD) and Absorbance difference (AD) methods coupled with corresponding spectrum subtraction method (SS). Window III; based on manipulation of the data of ratio spectra via Constant value coupled with constant subtraction (CV-CS) and novel Induced dual amplitude difference (IDAD) method coupled with corresponding spectrum subtraction method (SS). Finally, window IV; based on manipulation of the data of derivative of the ratio spectrum of the mixture via novel Factorized derivative ratio null contribution (FDD-NC) and Factorized unlimited derivative ratio (FUDD) methods coupled with corresponding spectrum subtraction method (SS). Synthetic mixtures and commercial medicine were constructively analyzed using the proposed methods while maintaining calibration graphs to be linear over ranges; 4.0-40.0 µg/mL for ACE, 2.0-14.0 µg/mL for PAR and 4.0-30.0 µg/mL for RAB. Moreover, methods' validation was confirmed via performing exhaustive statistical treatment of the experimental findings. The proposed methodologies can be used for the routine analysis of the cited drugs in quality control laboratories. Additionally, Spectral Similarity Index (SSI) was calculated to detect counterfeit products and methods' greenness profile was finally guaranteed through analytical greenness (AGREE) metric assessment tool.

Different approaches for the assessment of greenness of spectrophotometric methodologies utilized for resolving the spectral overlap of newly approved binary hypoglycemic pharmaceutical mixture

Simultaneous measurement of saxagliptin hydrochloride (SAG) and dapagliflozin propanediol monohydrate (DAG) in bulk powder, laboratory-prepared mixtures, and pharmaceutical dosage form were applied by utilizing three precise and sensitive spectrophotometric techniques which were developed and validated. The first method was the induced dual-wavelength approach (IDW), which relied primarily on the use of alternative equality factors (F) to abolish the effect of DAG when determining SAG and vice versa. The ratio difference method (RDM) was the second method, which used 25 μg/ml of DAG and 20 μg/ml of SAG as divisors to determine the amplitude difference on the ratio spectrum of SAG and DAG, respectively. SAG was determined at λ_max 221 nm after plateau subtraction followed by multiplication by the divisor of DAG 25 μg/ml using the third method, ratio subtraction coupled with extended ratio subtraction method (RSER). Subsequently, using an extension ratio subtraction of the spectra, DAG was determined at λ_max 225 nm was determined. The developed methods were effectively used to estimate SAG and DAG in laboratory-prepared mixtures and pharmaceutical dosage forms, with satisfactory recoveries. The methodologies were assessed for their environmental friendliness using the analytical eco-scale, analytical GREEnness calculator, and green analytical procedureindex (GAPI). These methodologies were validated following the International Conference on Harmonisation (ICH) requirements. A statistical comparison of the obtained findings to those of the published method revealed no significant differences in precision and accuracy. Because of their high precision and cost-effectiveness, the developed methods can be used in quality control laboratories to determine the binary mixture.

Simultaneous spectrophotometric determination of drug components from their dosage formulations

Spectrophotometry is a quick and reliable method for determining the composition of a variety of complex drug mixtures. Several mathematical models are available for the resolution of complex multicomponent UV spectra. UV spectrophotometric methods have the inherent capacity to resolve the interlaced spectra of complex mixtures quickly and appropriately, particularly for quantitative determination of components of mixture where several costly tools are not available. These methods also have the benefit of lower operational costs as they are operated using lesser amounts of analytical grade solvents and generate less waste. In this review, we discussed the theoretical background of different UV spectrometric methods for quantitative analysis of drug mixtures. The main focus of this review is to describe and report applications of extended Beer's law-based multicomponent analysis and to highlight the recent developments in the simultaneous determination of drug components from their complex mixtures.

Simultaneous quantification of total carbohydrate and protein amounts from aqueous solutions by the sulfuric acid ultraviolet absorption method (SA-UV method)

Based on the sulfuric acid-ultraviolet assay (SA-UV, developed by Albalasmeh et al., 2013), we have further expanded this method for the simultaneous quantification of saccharides (carbohydrates) and proteins by ultraviolet spectrophotometry. The absorbance of saccharides depends on the formation of furfurals by dehydration in the presence of concentrated sulfuric acid, whereas proteins are unaffected and can be quantified by UV active peptide bonds and aromatic amino acid residues. In saccharide/protein mixtures the SA-UV assay offers a good alternative and substitutes the need for two different methods, like the phenol-sulfuric acid (PSA, developed by DuBois et al., 1951) and bicinchoninic acid (BCA, developed by Smith et al., 1985) assays. For the development of this method, we used glucose and BSA as model substrates and performed a method validation in terms of linearity, LOD, LOQ, accuracy, and precision. Simultaneous quantification in glucose/BSA mixtures is possible down to 20 mg/L from 30 μL sample volumes, and even low content mixtures with concentrations down to 2 mg/L can appropriately be quantified from higher volumes by an evaporation technique.

Evaluation of vinburnine in pharmaceuticals by smart spectrophotometric methods; full stability study

Vinburnine (VNB) is a vinca alkaloid used as a vasodilator to enhance cerebral circulatory insufficiency. It is a cyclic amide containing drug which is expected to be sensitive to hydrolytic degradation. The degradation profile of VNB was studied in this work following ICH recommendations for stability study. The drug was sensitive only to degradation with NaOH with the formation of the carboxylic acid derivative, identified by IR and ¹H NMR analyses as 2-((1S,12bS)-1-ethyl-1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a] quinolizin-1-yl) acetic acid, (DEG). In this study five simple, smart and univariate stability indicating spectrophotometric methods were developed and validated for simultaneous determination of VNB and DEG for the first time. The developed methods include; Dual Wavelength Method (DWM), Dual Wavelength Resolution Method (DWRM), Factorized Absorbance Difference Method (FADM), Advanced Absorbance Subtraction Method (AASM), and Derivative Amplitude Factor Method (DAFM). These methods were capable of determination of VNB and DEG over the ranges of 1-30 and 3-50 µg/mL, respectively. The proposed methods were simple, smart, specific, and could be applied for analyzing synthetic mixtures of VNB and DEG and were successfully applied for determination of the drug in commercially available capsules. The obtained results of these methods were statistically compared with the reported HPLC one using student's-t and F- tests, where no significant difference was observed. Validation of the developed methods was applied according to ICH recommendations and all the results were within the acceptable limits.

Induced mathematical filtration as an innovative strategy for discrimination and estimation of glycemic control drugs in fixed dose combination

An innovative strategy was developed for the estimation of a fixed dose combination containing Alogliptin (ALO) and pioglitazone (PIO) using induced concept for resolving the overlapped spectra, lacking isoabsorptive point. This strategy is based on coupling factors as numerical values or ratios as spectrum form with the recorded signals leading to induced mathematical filtration of the drug of interest and complete elimination of the interfering one in the combination without prior physical separation. The calculated factors were factor of equality in induced dual wavelength (IDW) or absorptivity factor in induced concentration subtraction method (ICS) while absorptivity ratio spectrum for induced amplitude modulation method (IAM). The calibration curves displayed linearity within 1.0–16.0 μg/mL for ALO and 2.0–22.0 μg/mL for PIO with good correlation coefficients. The induced methods specificity was also assured through the assaying different synthetic mixtures prepared to contain the two drugs in ratios approaching the ratio actually found in the marketed dosage form. The methods were applicable and suitable for estimating ALO and PIO in both bulk form and their fixed dose combination. Induced methods have been extensively validated in accordance with ICH guidelines and results demonstrated the accuracy and reproducibility in comparison to the reported method.

Separation-free spectrophotometric platforms for rapid assessment of combined antiplatelet therapy in complex matrices

Aim: To develop simple and rapid UV-spectrophotometric platforms for the simultaneous quantification of a binary mixture containing clopidogrel bisulphate (CPS) and aspirin (ASP) in complex matrices without prior separation. Experimental: Five mathematical models namely ratio-difference method, mean centering of the ratio spectra, dual wavelength, induced dual wavelength and H-Point Standard Addition method, were utilized for resolving spectral overlap by mathematical processing of ratio and zero-order absorption spectra. Analytes were extracted from tested matrices (whole blood, pharmaceutical formulations and dissolution media buffer) and quantified using the proposed methods. The methods were validated according to ICH guidelines. Results: The developed methods demonstrated limits of detection ranging from 0.67 to 1.09 μg/ml-1 for CPS and 0.49 to 0.71 μg.ml-1 for ASP. All proposed methods allowed for reliable determination of CPS and ASP in complex matrices within reported reference ranges, indicating their potential application for therapeutic drug monitoring and quality control testing.

Advanced approaches for the treatment and amplification of weak spectral signals produced by critical concentrations in white multicomponent systems

An analytical investigation was carried out to study the treatment and amplification of the spectral signals produced by critical concentrations with high accuracy and precision using two advanced approaches. The factorized-spectrum approach was applied through two novel methods which were: absorptivity centering technique via both: factorized zero order absorption spectrum (ACT-FSD⁰_ΔA) and factorized ratio spectrum (ACT-FSR_ΔP). The proposed methods were found to be linear in the ranges of (15-100 μg/mL) and (3-40 μg/mL) for ASP and MTO, respectively. Those methods were compared to the methods following the geometrical standard addition approach: ratio H-point standard addition method (RHPSAM) and geometrical induced amplitude modulation (GIAM). The approaches were applied for the determination of the minor component metoclopramide in its mixture with the major component aspirin in the challengeable ratio of (1,90) respectively in a white multicomponent system. The results obtained from the proposed approaches were statistically compared with each other. The methods were validated according to ICH guidelines where the results were found to be within the acceptable limits. The methods were found to be accurate and reliable for the determination of metoclopramide critical concentration besides aspirin concentration. The results of single factor ANOVA analysis indicated that there is no significant difference among the developed methods. These methods provided simple resolution of this binary combination from synthetic mixtures and pharmaceutical preparation and can be conveniently adopted for routine quality control analysis.

Developing spectral numerical factor technique for the determination of amlodipine besylate and the latest generation of statins in their new pharmaceutical combination

Spectral numerical factor techniques have been developed for quantification of a new pharmaceutical combination. Five simple, fast and accurate spectrophotometric methods using spectral factor manipulation have been tested and validated so as to determine quantitatively a new fixed-dose combination tablet containing both amlodipine besylate (ADB) and rosuvastatin calcium (ROS). Namely, these methods are induced dual wavelength, absorbance correction, absorbance subtraction, amplitude correction and advanced amplitude subtraction. Their corresponding spectral factors are equality, absorption, absorbance, amplitude and unity factor, respectively. Calibration curves of ADB and ROS were set up for all the previously mentioned methods under the optimum conditions in a concentration range of 3.0-21.0 μg/mL with correlation coefficients ≥0.9990. Selectivity was calculated by analyzing laboratory-prepared synthetic blends of the cited drugs. A comparative study between these methods and the reported ones has been carried out statistically forming a judgment that the difference between both results is totally insignificant. Actually, the suggested spectral factor technique is so effective for use in routine laboratory essay owing to its simplicity, rapidity and precision. Generally, the proposed factor procedures have the ability to run smoothly without any interference from additives that may deteriorate analysis efficiency of a pharmaceutical combination.

Study of efficiency and spectral resolution for mathematical filtration technique using novel unlimited derivative ratio and classical univariate spectrophotometric methods for the multicomponent determination-stability analysis

Six simple, sensitive and selective spectrophotometric methods based on mathematical filtration technique are presented for concurrent determination of aceclofenac (ACE) and paracetamol (PAR) in presence of their degradation products, namely; diclofenac sodium (DIC) and 4-aminophenol (4-AP), respectively without preliminary physical separation procedures. This technique consists of several consecutive steps applied on built-in spectrophotometer software utilizing zero and/or derivative and/or ratio spectra of the studied components. These methods, namely, dual wavelength (DW), induced dual wavelength (IDW), derivative subtraction (DS) coupled with constant multiplication (CM), ratio difference method (RD), constant center method (CC) and the novel introduced unlimited derivative ratio method (UDD). This novel method has a very powerful competence for the analysis of the challengeable mixtures lacking zero crossing point. The linearity, accuracy and precision ranges of these methods were determined and validated as per ICH guidelines. Moreover, the specificity was checked by analyzing synthetic mixtures of both drugs. These methods were applied for the determination of the cited drugs in pharmaceutical formulation and a statistical comparison of the obtained results was made with each other and with those of reported spectrophotometric method. The comparison of the results of pure powder form showed that there is no significant difference between the proposed methods and the reported method regarding both accuracy and precision.

Earth-friendly spectrophotometric methods for simultaneous determination of ledipasvir and sofosbuvir: Application to average content and uniformity of dosage unit testing

Simple, rapid, sensitive, accurate, precise and earth-friendly spectrophotometric methods were developed for the simultaneous analysis of ledipasvir (LED) and sofosbuvir (SOF) without interference of both sunset yellow dye and copovidone excipients (the most probable interferents) in their combined dosage form. These proposed methods were based on measurement of LED in synthetic mixtures and combined dosage form by first derivative (¹D) spectrophotometry at 314 nm over the concentration range of 2-50 μg mL^-1 with coefficient of determination (R²) > 0.9999, mean percentage recovery of 99.98 ± 0.62. On the other hand, SOF in synthetic mixtures and combined dosage form was determined by five methods. Method I is based on the use of ¹D spectrophotometry at 274.2 nm (zero crossing point of LED). Method II involves the application of conventional dual wavelength method (DW) at the absolute difference between SOF zero order amplitudes at 261 nm (λ_max of SOF) and 364.7 nm. At these wavelengths, the absolute difference between LED zero order amplitudes was observed to equal zero. Method III depends on isosbestic point method (ISP) in which the total concentration of both drugs was measured at isosbestic point at 262.7 nm. Concentration of SOF could be obtained by subtraction of LED concentration. While, method IV depends on absorbance correction method (absorption factor method), which is based on determination of SOF concentration at 262.7 nm (λ_ISP) and LED at 333 nm (λ_max of LED). Finally, method V depends on absorbance ratio method (Q-analysis) in which 262.7 nm (λ_ISP) and 261 nm (λ_max of SOF) were selected to determine SOF concentration. The linearity range for all methods for SOF determination was 2-50 μg mL^-1 with coefficient of determination (R²) > 0.9999. Methods I, II & III were also applied for determination of SOF concentration in single dosage form. Their mean percentage recoveries were 100.35 ± 1.85, 99.97 ± 0.54 and 100.03 ± 0.49, for the three methods respectively. The proposed methods were validated according to international conference of harmonization (ICH) requirements and statistically compared to published reference methods. The ANOVA test confirmed that there is no significant differences between the proposed methods, and can be used for routine analysis of LED and SOF in commercial tablets. These developed methods were applied to estimate the average content and uniformity of dosage unit for LED/SOF combined dosage form and SOF single dosage form according to British pharmacopeia (BP) requirements.

Smart spectrophotometric methods based on normalized spectra for simultaneous determination of alogliptin and metformin in their combined tablets

Alogliptin (ALO) and metformin (MET) are coformulated for the treatment of type II diabetes mellitus. ALO is estimated at its λ_max 277 nm (⁰D), while MET was determined accurately by four spectrophotometric methods with minimum manipulation steps based on normalized division spectrum namely; ratio difference, advanced amplitude modulation, first derivative ratio (¹DD) and mean centering of the ratio spectra spectrophotometric methods. Linearity was acceptable over the concentration ranges of 5-40 and 2-16 μg/mL for ALO and MET, respectively. Accuracy and precision of the suggested methods were found to be within the acceptable limit. The specificity was inspected by analyzing laboratory prepared mixtures of the above drugs and their pharmaceutical preparation. The results of proposed and reported methods were statistically compared showing no significant difference regarding accuracy and precision. The developed methods could be applied for routine analysis of the cited drugs in quality control laboratories.

Validated stability-indicating spectrophotometric methods for the determination of Silodosin in the presence of its degradation products

Five simple, rapid, accurate, and precise spectrophotometric methods are developed for the determination of Silodosin (SLD) in the presence of its acid induced and oxidative induced degradation products. Method A is based on dual wavelength (DW) method; two wavelengths are selected at which the absorbance of the oxidative induced degradation product is the same, so wavelengths 352 and 377 nm are used to determine SLD in the presence of its oxidative induced degradation product. Method B depends on induced dual wavelength theory (IDW), which is based on selecting two wavelengths on the zero-order spectrum of SLD where the difference in absorbance between them for the spectrum of acid induced degradation products is not equal to zero so through multiplying by the equality factor, the absorption difference is made to be zero for the acid induced degradation product while it is still significant for SLD. Method C is first derivative (¹D) spectrophotometry of SLD and its degradation products. Peak amplitudes are measured at 317 and 357 nm. Method D is ratio difference spectrophotometry (RD) where the drug is determined by the difference in amplitude between two selected wavelengths, at 350 and 277 nm for the ratio spectrum of SLD and its acid induced degradation products while for the ratio spectrum of SLD and its oxidative induced degradation products the difference in amplitude is measured at 345 and 292 nm. Method E depends on measuring peak amplitudes of the first derivative of the ratio (¹DD) where peak amplitudes are measured at 330 nm in the presence of the acid induced degradation product and measured by peak to peak technique at 326 and 369 nm in the presence of the oxidative induced degradation product. The proposed methods are validated according to ICH recommendations. The calibration curves for all the proposed methods are linear over a concentration range of 5-70 μg/mL. The selectivity of the proposed methods was tested using different laboratory prepared mixtures of SLD with either its acid induced or oxidative induced degradation products showing specificity of SLD with accepted recovery values. The proposed methods have been successfully applied to the analysis of SLD in pharmaceutical dosage forms without interference from additives.

Comparative study of two different chromatographic approaches for quantitation of hydrocortisone acetate and pramoxine hydrochloride in presence of their impurities

In the present study, we compare the performance of two reversed-phase liquid chromatographic approaches using different eluents either conventional hydro-organic eluent or micellar one for simultaneous estimation of hydrocortisone acetate and pramoxine hydrochloride in presence of their degradants and process-related impurities; hydrocor-tisone and 4-butoxyphenol, respectively. For conventional reversed-phase liquid chromatography (RPLC), separation of the studied compounds was completed on an Inertsil ODS 3-C18 column (150 mm × 4.6 mm, 5 μm particle size) with a mobile phase consists of 50 mM phosphate buffer (pH 5.0): acetonitrile (50: 50, v/v). For micellar liquid chromatography (MLC), an Eclipse XDB-C8 column (150 mm × 4.6 mm, 5 μm particle size) was chosen for the separation with a green mobile phase consists of 0.15 M sodium dodecyl sulfate, 0.3% triethylamine and 10% n-butanol in 20 mM orthophosphoric acid (pH 5.0). Both methods were extended to analyze hydrocortisone acetate and pramoxine hydrochloride in their co-formulated cream. RPLC was superior to MLC with regard to sensitivity for the estimation of impurities. While, MLC represents an eco-friendly, less hazardous and biodegradable approach. Furthermore, the direct injection of the cream to the system without the need to laborious samples pretreatment, excessive amount of analysis time and/or use of large amount of toxic organic solvents is one of the outstanding advantages of MLC.

Innovative spectrophotometric methods for simultaneous estimation of the novel two-drug combination: Sacubitril/Valsartan through two manipulation approaches and a comparative statistical study

Different innovative spectrophotometric methods were introduced for the first time for simultaneous quantification of sacubitril/valsartan in their binary mixture and in their combined dosage form without prior separation through two manipulation approaches. These approaches were developed and based either on two wavelength selection in zero-order absorption spectra namely; dual wavelength method (DWL) at 226nm and 275nm for valsartan, induced dual wavelength method (IDW) at 226nm and 254nm for sacubitril and advanced absorbance subtraction (AAS) based on their iso-absorptive point at 246nm (λ_iso) and 261nm (sacubitril shows equal absorbance values at the two selected wavelengths) or on ratio spectra using their normalized spectra namely; ratio difference spectrophotometric method (RD) at 225nm and 264nm for both of them in their ratio spectra, first derivative of ratio spectra (DR¹) at 232nm for valsartan and 239nm for sacubitril and mean centering of ratio spectra (MCR) at 260nm for both of them. Both sacubitril and valsartan showed linearity upon application of these methods in the range of 2.5-25.0μg/mL. The developed spectrophotmetric methods were successfully applied to the analysis of their combined tablet dosage form ENTRESTO™. The adopted spectrophotometric methods were also validated according to ICH guidelines. The results obtained from the proposed methods were statistically compared to a reported HPLC method using Student t-test, F-test and a comparative study was also developed with one-way ANOVA, showing no statistical difference in accordance to precision and accuracy.

Different applications of isosbestic points, normalized spectra and dual wavelength as powerful tools for resolution of multicomponent mixtures with severely overlapping spectra

Background

Analysis of complex mixture containing three or more components represented a challenge for analysts. New smart spectrophotometric methods have been recently evolved with no limitation. A study of different novel and smart spectrophotometric techniques for resolution of severely overlapping spectra were presented in this work utilizing isosbestic points present in different absorption spectra, normalized spectra as a divisor and dual wavelengths. A quaternary mixture of drotaverine (DRO), caffeine (CAF), paracetamol (PCT) and para-aminophenol (PAP) was taken as an example for application of the proposed techniques without any separation steps. The adopted techniques adopted of successive and progressive steps manipulating zero /or ratio /or derivative spectra. The proposed techniques includes eight novel and simple methods namely direct spectrophotometry after applying derivative transformation (DT) via multiplying by a decoding spectrum, spectrum subtraction (SS), advanced absorbance subtraction (AAS), advanced amplitude modulation (AAM), simultaneous derivative ratio (S¹DD), advanced ratio difference (ARD), induced ratio difference (IRD) and finally double divisor–ratio difference-dual wavelength (DD-RD-DW) methods.

Results

The proposed methods were assessed by analyzing synthetic mixtures of the studied drugs. They were also successfully applied to commercial pharmaceutical formulations without interference from other dosage form additives. The methods were validated according to the ICH guidelines, accuracy, precision, repeatability, were found to be within the acceptable limits.

Conclusion

The proposed procedures are accurate, simple and reproducible and yet economic. They are also sensitive and selective and could be used for routine analysis of complex most of the binary, ternary and quaternary mixtures and even more complex mixtures.

Comparative study of novel versus conventional two-wavelength spectrophotometric methods for analysis of spectrally overlapping binary mixture

Smart spectrophotometric methods have been applied and validated for the simultaneous determination of a binary mixture of chloramphenicol (CPL) and prednisolone acetate (PA) without preliminary separation. Two novel methods have been developed; the first method depends upon advanced absorbance subtraction (AAS), while the other method relies on advanced amplitude modulation (AAM); in addition to the well established dual wavelength (DW), ratio difference (RD) and constant center coupled with spectrum subtraction (CC-SS) methods. Accuracy, precision and linearity ranges of these methods were determined. Moreover, selectivity was assessed by analyzing synthetic mixtures of both drugs. The proposed methods were successfully applied to the assay of drugs in their pharmaceutical formulations. No interference was observed from common additives and the validity of the methods was tested. The obtained results have been statistically compared to that of official spectrophotometric methods to give a conclusion that there is no significant difference between the proposed methods and the official ones with respect to accuracy and precision.

A comparative study of smart spectrophotometric methods for simultaneous determination of sitagliptin phosphate and metformin hydrochloride in their binary mixture

Simple, specific, accurate and precise spectrophotometric methods were developed and validated for the simultaneous determination of the oral antidiabetic drugs; sitagliptin phosphate (STG) and metformin hydrochloride (MET) in combined pharmaceutical formulations. Three methods were manipulating ratio spectra namely; ratio difference (RD), ratio subtraction (RS) and a novel approach of induced amplitude modulation (IAM) methods. The first two methods were used for determination of STG, while MET was directly determined by measuring its absorbance at λmax 232 nm. However, (IAM) was used for the simultaneous determination of both drugs. Moreover, another three methods were developed based on derivative spectroscopy followed by mathematical manipulation steps namely; amplitude factor (P-factor), amplitude subtraction (AS) and modified amplitude subtraction (MAS). In addition, in this work the novel sample enrichment technique named spectrum addition was adopted. The proposed spectrophotometric methods did not require any preliminary separation step. The accuracy, precision and linearity ranges of the proposed methods were determined. The selectivity of the developed methods was investigated by analyzing laboratory prepared mixtures of the drugs and their combined pharmaceutical formulations. Standard deviation values were less than 1.5 in the assay of raw materials and tablets. The obtained results were statistically compared to that of a reported spectrophotometric method. The statistical comparison showed that there was no significant difference between the proposed methods and the reported one regarding both accuracy and precision.