Simultaneous determination of retinoic acid and hydroquinone in skin ointment using spectrophotometric technique (ratio difference method)

Comparative statistical evaluation of greenness, blueness, and whiteness spectrophotometric methods for dexamethasone and chloramphenicol estimation

Five sustainable and validated UV spectrophotometric methods were developed for analyzing chloramphenicol (CHL) and dexamethasone sodium phosphate (DSP) in pure and ophthalmic dosage forms. CHL was detected by zero order spectra method at 292.0 nm in the range 2.00-32.00 µg/mL with limits of detection (LOD) and quantification (LOQ) of 0.96 and 2.88, respectively. DSP was analyzed using the following four techniques: Induce dual wavelength (IDW), fourier self-deconvolution (FSD), ratio difference (RD), and derivative ratio (DD1). The IDW method used at 239.0 and 254.0 nm with a linearity range of 4.00-40.00 µg/mL with LOD and LOQ values were 0.93 and 2.79, respectively. The FSD approach used at 242.0 nm, with a linearity range of 2.00-32.00 µg/mL and 0.65, 1.95 as values of LOD and LOQ, respectively. In the linearity range of 4.00-32.00 µg/mL, RD and DD1 are applied. RD is utilized at 225.0-240.0 nm, while DD1 is carried out at 249.0 nm. Values of LOD and LOQ for RD were 0.70 and 2.10 while for DD1 were 0.80 and 2.40, respectively. These methods were evaluated for their environmental sustainability and validated according to ICH guidelines, overcoming challenges like spectral overlap and collinearity. Statistical comparisons with published methods revealed no significant differences.

Chemical Derivatization and Paper Spray Ionization Mass Spectrometry for Fast Screening of Retinoic Acid in Cosmetics

As a prescription drug, retinoic acid is listed as a banned cosmetic additive in the EU and China regulations. Currently, spectrophotometric methods, including thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), and HPLC-MS/MS, are commonly used for the determination of retinoic acid. As these conventional methods require complex pretreatment and are time-consuming, chemical derivatization combined with paper spray ionization mass spectrometry was developed for the fast detection of retinoic acid in cosmetics. N,N-dimethylpiperazine iodide (DMPI) was utilized as a derivatization reagent. Carboxylic acid in retinoic acid was derivatized to carry a positive charge and was subjected to mass spectrometry analysis. Results showed that compared with non-derivatized compounds, the detection limit was increased by about 50 times. The linearity in the range of 0.005-1 μg·mL-1 was good. The limit of detection (LOD) was 0.0013 μg·mL-1, and the limit of quantification (LOQ) was 0.0043 μg·mL-1. The recoveries of spiked samples were in the range of 95-105%, and the RSDs were below 5%. Derivatization and paper spray ionization MS render a quick, sensitive, and accurate method for the detection of retinoic acid in a complex matrix.

Different spectrophotometric methods for simultaneous quantitation of Vericiguat and its alkaline degradation product: a comparative study with greenness profile assessment

Investigations concerning novel drugs and their induced degradation products are necessary for clinical research and quality control in the pharmaceutical industry. Four spectrophotometric techniques have been performed for simultaneous quantitation of Vericiguat (VER) and its alkali-induced degradation product (ADP) without prior separation. Method A is a dual wavelength method (DW) that estimates the absorbance difference at 314-328 nm, and 246-262 nm for VER and ADP; respectively. Method B uses a ratio difference method (RD) to estimate the ratio spectrum's amplitude difference (DP318-342) and (DP284-292) for VER and ADP; respectively. Method C uses a first derivative ratio method (1DD) to estimate the peak ratio spectrum amplitude of the first derivative at 318 and 275 nm for VER and ADP; respectively. Method D uses the mean centering of the ratio spectra (MCR) to estimate amplitude values for VER and ADP at 337 and 292 nm; respectively. In a concentration range of 5.00-50.00 µg/mL for VER and 5.00-100.00 µg/mL for ADP, the methods were validated following ICH criteria and utilized to estimate VER in bulk and its dosage form. The methods' greenness was assessed via three tools: the green analytical procedure index (GAPI), analytical eco-scale, and analytical greenness assessment (AGREE).

Application of LTA zeolite-modified electrode for sensitive detection of retinoic acid in tap water

An electrochemical method based on a Linde Type-A zeolite-modified glass carbon electrode (LTA/GCE) was introduced for the determination of retinoic acid (RA). LTA zeolite could be synthesized through a hydrothermal method and served as a commercial electrochemical sensor with high stability and sensitivity in electrochemical progress. The as-synthesized product was characterized by scanning electron microscopy (SEM), differential thermal analysis (DTA), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Under optimal conditions, a detection limit of 0.8 μM was obtained for RA with a linear range of 0.8-20.1 μM. This electrochemical method for determining RA was simpler and cheaper than previously reported methods. Furthermore, the modified electrode could be applied to the detection of RA in tap water, achieving a linear range of 1.4-15.0 μM with a detection limit of 1.4 μM and good recovery. The modified electrode designed by this method provided good selectivity, stability, and reproducibility for RA determination and reliable application for the analysis of RA in environmental water.

Eco-friendly resolution of spectrally overlapping signals of a combined triple-action over-the-counter pharmaceutical formulation for symptomatic management of COVID-19 pandemic: application to content uniformity testing

Currently, all researchers are concentrating their efforts on countering the COVID-19 pandemic. The majority of patients are managed at home, according to recent statistics. An OTC triple action combination comprising paracetamol (PAR), aspirin (ASP), and diphenhydramine (DIPH) is commonly given for pain relief, fever control, and as a night-time sleep aid. This combination is currently recommended for COVID-19 patients as part of symptomatic treatment and management. In this work, three smart, simple, accurate, eco-friendly, and cost-effective spectrophotometric methods are developed for simultaneous determination of PAR, ASP, and DIPH in their combined over-the-counter caplet dosage form without any prior separation steps. The first method is the first derivative spectrophotometry (D¹) which determined PAR at 259.7 nm. The second one is the dual-wavelength in ratio spectra (DWRS) for determination of ASP at 214.1 and 220.1 nm after using 10.0 μg/mL of PAR as a divisor, where PAR was a constant, and the wavelengths difference equal to zero for DIPH. The third method is the double divisor-ratio difference spectrophotometric one (DD-RD) which was based on using the sum of 15.0 µg/mL of each of PAR and ASP as a double divisor, and the difference in amplitudes was measured at two wavelengths ∆P_{(214.5–226.0)} for determination of DIPH. The developed methods have been validated as per ICH guidelines. Furthermore, the three suggested methods were employed successfully to assay marketed pharmaceutical formulation and to investigate the content uniformity of the dosage units in accordance with the United States Pharmacopeia's guidelines. Finally, the greenness profile of the proposed methods was assessed and compared with the reported method using the analytical eco-scale system, national environmental method index (NEMI), green analytical procedure index (GAPI), and analytical greenness (AGREE) metric. The results from the proposed methods statistically agreed with those obtained by the reported one, with no significant differences in accuracy and precision.

Different Approaches in Manipulating Ratio Spectra for Analyzing Amlodipine Besylate and Irbesartan Combination

Background

Hypertension is a key risk factor for ischemic heart disease and atherosclerosis. Most patients require a combination of antihypertensive medications to accomplish their therapeutic goals. Antihypertensive medicines such as calcium channel blockers and angiotensin receptor blockers are indicated for patients whose high blood pressure cannot be controlled with monotherapy. The combination of amlodipine besylate (AML) with irbesartan (IRB) is an example of this synergistic activity in lowering blood pressure.

Objective

In this regard, the goal of the research is to develop sensitive spectrophotometric methods for the simultaneous determination of amlodipine besylate and irbesartan.

Methods

Three simple ratio spectra-manipulating spectrophotometric methods namely, ratio difference, mean centering of ratio spectra, and derivative ratio, were developed for the simultaneous assay of the cited mixture.

Results

Linear correlations were attained over the concentration range of 1–35 μg/mL and 2–35 μg/mL for amlodipine besylate and irbesartan, respectively. The methods were validated according to the International Conference on Harmonization guidelines with good results.

Conclusion

The methods developed were successfully applied for the assay of the cited drugs in their marketed formulation. They could be efficiently used for routine analysis of the mentioned drugs in QC laboratories.

Highlights

The proposed approaches do not require expensive solvents or complex instruments. They could be used in routine laboratory tests where time and cost are crucial.

A modified carbon paste electrode with N-rGO/CuO nanocomposite and ionic liquid for the efficient and cheap voltammetric sensing of hydroquinone in water specimens

This paper reports a voltammetric sensor based on copper oxide nanoparticles on nitrogen-doped reduced graphene oxide nanocomposite (N-rGO/CuO)-ionic liquid modified carbon paste electrode (N-rGO/CuO-ILCPE) for determining the hydroquinone (HQ). The N-rGO/CuO was prepared by a facile protocol, followed by characterization via fourier transform-infrared (FT-IR) patterns, field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD) analysis. The electrochemical behaviour was linearly symmetrical to various hydroquinone levels (1.0-600.0 μM) with a narrow limit of detection (LOD = 0.25 μM). The diffusion coefficient was also estimated to be 4.1 × 10^-6 cm²/s. The N-rGO/CuO-ILCPE was impressively applicable in determination of hydroquinone in the real specimens.

Smart spectrophotometric methods for stability assessment of two co-formulated antigout drugs

Simple, sensitive and accurate stability indicating spectrophotometric methods have been developed for the simultaneous determination of probenecid, colchicine as well as colchicine degradation product in their ternary mixture. Probenecid was firstly assayed using the double divisor ratio spectra derivative method. On the other hand, three spectrophotometric methods, namely: ratio difference, derivative ratio and mean centering of ratio spectra, have been suggested for the simultaneous quantification of colchicine and its degradation product. The obtained calibration curves were linear at 2.5-30.0 μg/mL, 0.5-25.0 μg/mL and 1.0-13.0 μg/mL for probenecid, colchicine and colchicine degradation product, respectively. The investigated methods were validated in accordance with the International Council for Harmonisation guidelines and were effectively used for quantification of probenecid and colchicine in their bulk powders and combined pharmaceutical dosage form.

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.

Specific sensing of resorcin based on the hierarchical porous nanoprobes constructed by cuttlefish-derived biomaterials through differential pulse voltammetry

The specific detection of resorcin from its isomers is a current research hotspot. Thus in our work, a ternary hierarchical porous nanoprobe has been constructed based on the combination of cuttlefish ink and bimetallic Au@Ag nanoclusters for the specific sensing of resorcin. Briefly, through electrostatic interaction, Au@Ag core-shell nanoclusters are immobilized on the surface of polydopamine extracted from cuttlefish, which is turned into nitrogen-doped porous carbon functionalized by bimetallic Au@Ag by topological transformation subsequently. Afterward, an electrochemical sensor is fabricated based on the nanoprobes for specifically determining resorcin in solution by differential pulse voltammetry, and the linear detection ranges of the sensor are 1-100 μM and 1.2-4 mM while the detection limit reaches 0.06 μM. Meanwhile, the sensing mechanism of resorcin by the pre-fabricated sensor is detailedly studied by density functional theory to obtain a clear electrochemical process. Besides, the selectivity, stability, plus reproducibility of the pre-fabricated sensor have been also tested, and the determinations for resorcin in real environmental water samples have also been performed with good recoveries, revealing the auspicious application potential in the environmental monitoring.

In vitro analytical dissolution profiling of antiemetic delayed release tablets in two different dissolution media: Validated spectrophotometric methods versus reported HPLC

The combination of pyridoxine HCl (PYR) and doxylamine succinate (DOX) was proved to be effective and safe acting as the first line of pregnancy medication for vomiting and nausea under a trade name; Vomibreak® delayed release tablets. This combination has been available in the Egyptian market since 2016. Dissolution study is a meaningful tool that represents a predictor of output because the rate controlling steps in any drug's absorption is the rate of discharging from its medicinal formulation. Generally, the dissolution test of all delayed release tablets is operated at two stages: first the acid stage then the buffer stage. In our work, the acid stage was performed in 0.1 N hydrochloric acid (0.1 M HCl) and the buffer one was in 0.2 M sodium phosphate buffer (0.2 M Na-PB), pH = 6.8, according to FDA guidelines. In present work, for the first time, this binary mixture was quantitatively determined by applying four spectrophotometric methods. PYR was directly determined by zero order spectra method (D⁰) at 291.0 nm in the range 2.0-26.0 μg/mL in the acid stage and at 325.0 nm in the range 5.0-35.0 μg/mL in the buffer stage, where DOX show no interference in both cases. However, DOX was determined by three methods, namely, Dual wavelength (DW), Ratio difference (RD) and Derivative ratio (DD¹). DD¹ was the chosen method for determination of DOX in the two-phase dissolution study of Vomibreak® tablets at 249.0 nm in the range 2.0-44.0 μg/mL and 273.0 nm in the range 5.0-100.0 μg/mL in acid and buffer phases, respectively. All of the suggested methods were tested in compliance with ICH guidelines, where all methods were found to be reliable, reproducible, and selective. A statistical comparison was computed between two analytical techniques of critical importance in the development of two media dissolution profile: proposed UV- spectrophotometric and reported HPLC methods where no significant difference was found. Difference (ƒ₁) and similarity (ƒ₂) factors were calculated for PYR and DOX and shown that ƒ₁ was 1.490 and 1.654 and ƒ₂ was 94.431 and 92.396 for PYR and DOX, respectively.

Green spectrophotometric methods for the determination of a binary mixture of lidocaine hydrochloride and cetylpyridinium chloride in the presence of dimethylaniline

Three green, simple, precise, accurate and sensitive spectrophotometric methods were developed for the determination of a binary mixture of lidocaine hydrochloride (LDC) and cetylpyridinium chloride (CPC) in the presence of dimethylaniline (DMA). In the three methods, the interference of DMA spectrum is eliminated using the ratio subtraction method. Method (A) depended on determining LDC and CPC by measuring the first derivative of the ratio spectra (¹DD) at 271.0 and 268.4 nm, respectively. Method (B) was the ratio difference (RD), based on dividing the absorption spectrum of the binary mixture by a standard spectrum of CPC or LDC, then measuring the amplitude difference of the ratio spectra (∆P) between 231.2 and 240.0 nm for LDC and between 242.8 and 258.0 nm for CPC. Method (C) based on the application of dual wavelength coupled with the isoabsorptive point method. This was achieved by measuring the absorbance difference (∆A) between 243.0 and 268.6 nm for the determination of LDC, followed by application of isoabsorptive point method comprised of measurement the total content of the mixture of LDC and CPC at their isoabsorptive point at 240.0 nm. The content of CPC was obtained by subtraction. The specificity of the developed methods was investigated by analyzing laboratory prepared mixtures containing different ratios of LDC and CPC in presence of DMA. The proposed methods displayed useful analytical characteristics for the determination of LDC and CPC in bulk powder and their combined dosage form. The obtained results were statistically compared with those obtained by the official methods, showing no significant difference with respect to accuracy and precision.

Smart spectrophotometric assessment of tamsulosin hydrochloride and tadalafil in their new pharmaceutical formulation for treatment of benign prostatic hyperplasia and erectile dysfunction

A novel combination of tamsulosin hydrochloride and tadalafil is recently available for treatment of benign prostatic hyperplasia and erectile dysfunction. For the first time, four simple, accurate, smart and robust spectrophotometric methods have been suggested for their simultaneous quantification. The methods, namely; first derivative, ratio difference, derivative ratio and mean centering of ratio spectra, successfully resolved the spectral overlap of their challenging binary mixture. Calibration curves were linear at 2.0-40.0 and 2.0-55.0 μg/mL for tamsulosin hydrochloride and tadalafil, respectively. The methods were validated according to ICH guidelines and statistically compared with the official ones, revealing no considerable difference with respect to accuracy and precision. Specificity of the developed methods was assessed by evaluating various laboratory prepared mixtures. Furthermore, the methods were successfully applied for the quantification of the two drugs in their combined dosage form.

A comparative study of different aspects in manipulating ratio spectra used for the analysis of cefradine in the presence of its alkaline degradation product

Six stability-indicating UV-spectrophotometric methods manipulating ratio spectra were utilized for the analysis of cefradine in presence of its alkaline degradate. These methods are different forms of transformations; ratio difference, mean centering, derivative ratio using numerical differentiation, derivative ratio using Savitsky-Golay filter, continuous wavelet transform and derivative continuous wavelet transform. Water was used as a solvent and the linearity ranges were 6-26 μg/mL. Determination of accuracy and precision for the suggested procedures were executed. Assessment of specificity was run through analyzing laboratory prepared mixtures containing cefradine and its alkaline degradate. The suggested methods were useful for cefradine estimation in tablets. Statistically, the outputs obtained from the recommended and published methods reveal no significant differences.

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.

Analytical investigation of different mathematical approaches utilizing manipulation of ratio spectra

This work represents a comparative study of different approaches of manipulating ratio spectra, applied on a binary mixture of ciprofloxacin HCl and dexamethasone sodium phosphate co-formulated as ear drops. The proposed new spectrophotometric methods are: ratio difference spectrophotometric method (RDSM), amplitude center method (ACM), first derivative of the ratio spectra (¹DD) and mean centering of ratio spectra (MCR). The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs. The proposed methods were validated according to the ICH guidelines. A comparative study was conducted between those methods regarding simplicity, limitations and sensitivity. The obtained results were statistically compared with those obtained from the reported HPLC method, showing no significant difference with respect to accuracy and precision.

Simultaneous determination of the brand new two-drug combination for the treatment of hepatitis C: Sofosbuvir/ledipasvir using smart spectrophotometric methods manipulating ratio spectra

In this work, various sensitive and selective spectrophotometric methods were first introduced for the simultaneous determination of sofosbuvir and ledipasvir in their binary mixture without preliminary separation. Ledipasvir was determined simply by zero-order spectrophotometric method at its λ_max=333.0nm in a linear range of 2.5-30.0μg/ml without any interference of sofosbuvir even in low or high concentrations and with mean percentage recovery of 100.05±0.632. Sofosbuvir can be quantitatively estimated by one of the following smart spectrophotometric methods based on ratio spectra developed for the resolution of the overlapped spectra of their binary mixture; ratio difference spectrophotometric method (RD) by computing the difference between the amplitudes of sofosbuvir ratio spectra at 228nm and 270nm, first derivative (DD¹) of ratio spectra by measuring the sum of amplitude of trough and peak at 265nm and 277nm, respectively, ratio subtraction (RS) spectrophotometric method in which sofosbuvir can be successfully determined at its λ_max=261.0nm and mean centering (MC) of ratio spectra by measuring the mean centering values at 270nm. All of the above mentioned spectrophotometric methods can estimate sofosbuvir in a linear range of 7.5-90.0μg/ml with mean percentage recoveries of 100.57±0.810, 99.92±0.759, 99.51±0.475 and 100.75±0.672, respectively. These methods were successfully applied to the analysis of their combined dosage form and bulk powder. The adopted methods were also validated as per ICH guidelines and statistically compared to an in-house HPLC method.

Spectrophotometric Methods for Simultaneous Determination of Oxytetracycline HCl and Flunixin Meglumine in Their Veterinary Pharmaceutical Formulation

Four precise, accurate, selective, and sensitive UV-spectrophotometric methods were developed and validated for the simultaneous determination of a binary mixture of Oxytetracycline HCl (OXY) and Flunixin Meglumine (FLU). The first method, dual wavelength (DW), depends on measuring the difference in absorbance (ΔA 273.4-327 nm) for the determination of OXY where FLU is zero while FLU is determined at ΔA 251.7-275.7 nm. The second method, first-derivative spectrophotometric method (1D), depends on measuring the peak amplitude of the first derivative selectively at 377 and 266.7 nm for the determination of OXY and FLU, respectively. The third method, ratio difference method, depends on the difference in amplitudes of the ratio spectra at ΔP 286.5-324.8 nm and ΔP 249.6-286.3 nm for the determination of OXY and FLU, respectively. The fourth method, first derivative of ratio spectra method (1DD), depends on measuring the amplitude peak to peak of the first derivative of ratio spectra at 296.7 to 369 nm and 259.1 to 304.7 nm for the determination of OXY and FLU, respectively. Different factors affecting the applied spectrophotometric methods were studied. The proposed methods were validated according to ICH guidelines. Satisfactory results were obtained for determination of both drugs in laboratory prepared mixture and pharmaceutical dosage form. The developed methods are compared favourably with the official ones.

Simultaneous determination of Fluticasone propionate and Azelastine hydrochloride in the presence of pharmaceutical dosage form additives

Fluticasone propionate (FLU) and Azelastine hydrochloride (AZE) are co-formulated with phenylethyl alcohol (PEA) and Benzalkonium chloride (BENZ) (as preservatives) in pharmaceutical dosage form for treatment of seasonal allergies. Different spectrophotometric methods were used for the simultaneous determination of cited drugs in the dosage form. Direct spectrophotometric method was used for determining of AZE, while Derivative of double divisor of ratio spectra (DD-RS), Ratio subtraction coupled with ratio difference method (RS-RD) and Mean centering of the ratio spectra (MCR) are used for the determination of FLU. The linearity of the proposed methods was investigated in the range of 5.00-40.00 and 5.00-80.00μg/mL for FLU and AZE, respectively. The specificity of the developed methods was investigated by analyzing laboratory prepared mixtures containing different ratios of cited drugs in addition to PEA and their pharmaceutical dosage form. The validity of the proposed methods was assessed using the standard addition technique. The obtained results were statistically compared with those obtained by official or the reported method for FLU or AZE, respectively showing no significant difference with respect to accuracy and precision at p=0.05.

Stability-indicating spectrophotometric methods for determination of the anticoagulant drug apixaban in the presence of its hydrolytic degradation product

Apixaban (a novel anticoagulant agent) was subjected to a stress stability study including acid, alkali, oxidative, photolytic, and thermal degradation. The drug was found to be only liable to acidic and alkaline hydrolysis. The degradation product was then isolated and identified by IR and GC-mass spectrometry. Four spectrophotometric methods, namely; first derivative (D(1)), derivative ratio (DR), ratio difference (RD) and mean centering of ratio spectra (MCR), have been suggested for the determination of apixaban in presence of its hydrolytic degradation product. The proposed methods do not require any preliminary separation step. The accuracy, precision and linearity ranges of the proposed methods were determined, and the methods were validated as per ICH guidelines and the specificity was assessed by analyzing synthetic mixtures containing different percentages of the degradation product with the drug. The developed methods were successfully applied for the determination of apixaban in bulk powder and its tablet dosage form.

Successive ratio subtraction coupled with constant multiplication spectrophotometric method for determination of hydroquinone in complex mixture with its degradation products, tretinoin and methyl paraben

A sensitive and selective stability-indicating successive ratio subtraction coupled with constant multiplication (SRS-CM) spectrophotometric method was studied and developed for the spectrum resolution of five component mixture without prior separation. The components were hydroquinone in combination with tretinoin, the polymer formed from hydroquinone alkali degradation, 1,4 benzoquinone and the preservative methyl paraben. The proposed method was used for their determination in their pure form and in pharmaceutical formulation. The zero order absorption spectra of hydroquinone, tretinoin, 1,4 benzoquinone and methyl paraben were determined at 293, 357.5, 245 and 255.2 nm, respectively. The calibration curves were linear over the concentration ranges of 4.00-46.00, 1.00-7.00, 0.60-5.20, and 1.00-7.00 μg mL(-1) for hydroquinone, tretinoin, 1,4 benzoquinone and methyl paraben, respectively. The pharmaceutical formulation was subjected to mild alkali condition and measured by this method resulting in the polymerization of hydroquinone and the formation of toxic 1,4 benzoquinone. The proposed method was validated according to ICH guidelines. The results obtained were statistically analyzed and compared with those obtained by applying the reported method.

Comparative Study of Novel Ratio Spectra and Isoabsorptive Point Based Spectrophotometric Methods: Application on a Binary Mixture of Ascorbic Acid and Rutin

This paper presents novel methods for spectrophotometric determination of ascorbic acid (AA) in presence of rutin (RU) (coformulated drug) in their combined pharmaceutical formulation. The seven methods are ratio difference (RD), isoabsorptive_RD (Iso_RD), amplitude summation (A_Sum), isoabsorptive point, first derivative of the ratio spectra ((1)DD), mean centering (MCN), and ratio subtraction (RS). On the other hand, RU was determined directly by measuring the absorbance at 358 nm in addition to the two novel Iso_RD and A_Sum methods. The work introduced in this paper aims to compare these different methods, showing the advantages for each and making a comparison of analysis results. The calibration curve is linear over the concentration range of 4-50 μg/mL for AA and RU. The results show the high performance of proposed methods for the analysis of the binary mixture. The optimum assay conditions were established and the proposed methods were successfully applied for the assay of the two drugs in laboratory prepared mixtures and combined pharmaceutical tablets with excellent recoveries. No interference was observed from common pharmaceutical additives.

Novel ratio difference at coabsorptive point spectrophotometric method for determination of components with wide variation in their absorptivities

Different methods have been introduced to enhance selectivity of UV-spectrophotometry thus enabling accurate determination of co-formulated components, however mixtures whose components exhibit wide variation in absorptivities has been an obstacle against application of UV-spectrophotometry. The developed ratio difference at coabsorptive point method (RDC) represents a simple effective solution for the mentioned problem, where the additive property of light absorbance enabled the consideration of the two components as multiples of the lower absorptivity component at certain wavelength (coabsorptive point), at which their total concentration multiples could be determined, whereas the other component was selectively determined by applying the ratio difference method in a single step. Mixture of perindopril arginine (PA) and amlodipine besylate (AM) figures that problem, where the low absorptivity of PA relative to AM hinders selective spectrophotometric determination of PA. The developed method successfully determined both components in the overlapped region of their spectra with accuracy 99.39±1.60 and 100.51±1.21, for PA and AM, respectively. The method was validated as per the USP guidelines and showed no significant difference upon statistical comparison with reported chromatographic method.

Comparative study on the selectivity of various spectrophotometric techniques for the determination of binary mixture of fenbendazole and rafoxanide

Five different spectrophotometric methods were applied for simultaneous determination of fenbendazole and rafoxanide in their binary mixture; namely first derivative, derivative ratio, ratio difference, dual wavelength and H-point standard addition spectrophotometric methods. Different factors affecting each of the applied spectrophotometric methods were studied and the selectivity of the applied methods was compared. The applied methods were validated as per the ICH guidelines and good accuracy; specificity and precision were proven within the concentration range of 5-50 μg/mL for both drugs. Statistical analysis using one-way ANOVA proved no significant differences among the proposed methods for the determination of the two drugs. The proposed methods successfully determined both drugs in laboratory prepared and commercially available binary mixtures, and were found applicable for the routine analysis in quality control laboratories.

Novel spectrophotometric method for selective determination of compounds in ternary mixtures (dual wavelength in ratio spectra)

A simple selective spectrophotometric method for determination of compounds in ternary mixture was developed by combining the resolution power of two well-known methods that are commonly used for binary mixtures; namely ratio difference method and dual wavelength. The new method (dual wavelength in ratio spectra) was successfully applied for the determination of a ternary mixture of betamethasone dipropionate (BM), clotrimazole (CT) and benzyl alcohol (BA) in pure powder form and in their pharmaceutical preparation. The difference in amplitudes (ΔP) in the ratio spectra at 252.0 and 258.0 nm (ΔP(252.0-258.0 nm)) corresponds to BM, while ΔP(266.8-255.4 nm) and ΔP(254.2-243.5 nm) corresponds to CT and BA, respectively. The method was validated as per the USP 2005 guidelines. The developed method can be used in quality control laboratories for routine analysis of compounds in ternary mixtures.

A comparative study between three stability indicating spectrophotometric methods for the determination of diatrizoate sodium in presence of its cytotoxic degradation product based on two-wavelength selection

Three sensitive, selective, and precise stability indicating spectrophotometric methods for the determination of the X-ray contrast agent, diatrizoate sodium (DTA) in the presence of its acidic degradation product (highly cytotoxic 3,5-diamino metabolite) and in pharmaceutical formulation, were developed and validated. The first method is ratio difference, the second one is the bivariate method, and the third one is the dual wavelength method. The calibration curves for the three proposed methods are linear over a concentration range of 2-24 μg/mL. The selectivity of the proposed methods was tested using laboratory prepared mixtures. The proposed methods have been successfully applied to the analysis of DTA in pharmaceutical dosage forms without interference from other dosage form additives. The results were statistically compared with the official US pharmacopeial method. No significant difference for either accuracy or precision was observed.

Different approaches in manipulating ratio spectra applied for the analysis of Cefprozil in presence of its alkaline-induced degradation product: a comparative study

Four simple, accurate and precise stability-indicating spectrophotometric methods manipulating ratio spectra were developed and validated for simultaneous determination of Cefprozil (CZ) and its alkaline-induced degradation product (DCZ) without prior separation namely; ratio difference, mean centering, derivative ratio using Savitsky-Golay filter and continuous wavelet transform. The accuracy, precision and linearity ranges of the proposed methods were determined. The methods were validated and the specificity was assessed by analyzing synthetic mixtures containing the drug and its degradate. The four methods were applied for the determination of the cited drug in tablets and the obtained results were statistically compared with those of a reported method. The comparison showed that there are no significant differences between the proposed methods and the reported method regarding both accuracy and precision.

Different signal processing techniques of ratio spectra for spectrophotometric resolution of binary mixture of bisoprolol and hydrochlorothiazide; a comparative study

Five signal processing techniques were applied to ratio spectra for quantitative determination of bisoprolol (BIS) and hydrochlorothiazide (HCT) in their binary mixture. The proposed techniques are Numerical Differentiation of Ratio Spectra (ND-RS), Savitsky-Golay of Ratio Spectra (SG-RS), Continuous Wavelet Transform of Ratio Spectra (CWT-RS), Mean Centering of Ratio Spectra (MC-RS) and Discrete Fourier Transform of Ratio Spectra (DFT-RS). The linearity of the proposed methods was investigated in the range of 2-40 and 1-22 μg/mL for BIS and HCT, respectively. The proposed methods were applied successfully for the determination of the drugs in laboratory prepared mixtures and in commercial pharmaceutical preparations and standard deviation was less than 1.5. The five signal processing techniques were compared to each other and validated according to the ICH guidelines and accuracy, precision, repeatability and robustness were found to be within the acceptable limit.

Five different spectrophotometric methods for determination of Amprolium hydrochloride and Ethopabate binary mixture

Five simple, specific, accurate and precise UV-spectrophotometric methods are adopted for the simultaneous determination of Amprolium hydrochloride (AMP) and Ethopabate (ETH), a binary mixture with overlapping spectra, without preliminary separation. The first method is first derivative of the ratio spectra ((1)DD) for determination of AMP and ETH at 234.7nm and 306.8nm respectively with mean percentage recoveries 99.76±0.907 and 100.29±0.842 respectively. The second method is the mean centering of the ratio spectra for determination of AMP and ETH at 238.8nm and 313nm respectively with mean percentage recoveries 100.26±1.018 and 99.94±1.286 respectively. The third method is based on dual wavelength selection for determination of AMP and ETH at 235.3nm & 308nm and 244nm & 268.4nm respectively with mean percentage recoveries 99.30±1.097 and 100.03±1.065 respectively. The fourth method is ratio difference method for determination of AMP and ETH at 239nm & 310nm and 239nm & 313nm respectively with mean percentage recoveries 99.27±0.892 and 100.40±1.814 respectively. The fifth one is area under the curve (AUC) method where the areas between 235.6-243nm and 268.3-275nm are selected for determination of AMP and ETH with mean percentage recoveries 100.35±1.031 and 100.39±0.956 respectively. These methods are tested by analyzing synthetic mixtures of the two drugs and they are applied to their pharmaceutical veterinary preparation. Methods are validated according to the ICH guidelines and accuracy, precision and repeatability are found to be within the acceptable limit.

Using Poly-L-Histidine Modified Glassy Carbon Electrode to Trace Hydroquinone in the Sewage Water

A sensitive voltammetric method for trace measurements of hydroquinone in the sewage water is described. The poly-L-histidine is prepared to modify the glassy carbon electrode in order to improve the electrochemical catalysis of interesting substances such as hydroquinone. The influence of the base solution, pH value, and scanning speed on the tracing of hydroquinone is discussed, and the experimental procedures and conditions are optimized. The laboratory results show that it is possible to construct a linear calibration curve between the peak current of hydroquinone on modified electrode and its concentration at the level of 0.00001 mol/L. The potential limitation of the method is suggested by a linear peaking shift model as well. The method was successfully applied to the determination of hydroquinone in the actual sample of industrial waste water.

Three different methods for determination of binary mixture of Amlodipine and Atorvastatin using dual wavelength spectrophotometry

Three simple, specific, accurate and precise spectrophotometric methods depending on the proper selection of two wavelengths are developed for the simultaneous determination of Amlodipine besylate (AML) and Atorvastatin calcium (ATV) in tablet dosage forms. The first method is the new Ratio Difference method, the second method is the Bivariate method and the third one is the Absorbance Ratio method. The calibration curve is linear over the concentration range of 4-40 and 8-32 μg/mL for AML and ATV, respectively. These methods are tested by analyzing synthetic mixtures of the above drugs and they are applied to commercial pharmaceutical preparation of the subjected drugs. Methods are validated according to the ICH guidelines and accuracy, precision, repeatability and robustness are found to be within the acceptable limit. The mathematical explanation of the procedures is illustrated.