Derivative Ratio Spectrophotometry Research Articles

Eco‐Friendly Analytical Approaches for the Quantification of Molnupiravir and Favipiravir Using Capillary Zone Electrophoresis and Derivative Ratio Spectrophotometry

AbstractDesigning new validated analytical procedures with a focus on many objectives, such as simplicity, environmental friendliness, analytical effectiveness, and sustainability, has grown to be a top priority in quality control departments. Applying green and white analytical chemistry concepts is no longer a luxury. In this report, two new approaches, Capillary Zone Electrophoresis (CZE) with Photo Diode Array (PDA) detection and derivative ratio spectrophotometric methods, are established and validated for the simultaneous analysis of molnupiravir (MLP) and favipiravir (FAV) in bulk, single dosage forms, and their expected combined dosage forms. For the two drugs, linearity ranges of 5–50 μg/mL and 1–30 μg/mL were achieved using the CZE and spectrophotometric methods, respectively. Both techniques have been validated and used for the estimation of the two medications in lab‐made capsules in accordance with the International Council for Harmonization's (ICH) recommendations. Seven assessment models were used to evaluate the greenness and sustainability of the introduced approaches compared to three previously published HPLC, chemometric, and HPTLC techniques. ChlorTox and BAGI tools are applied for the first time for the evaluation of an analytical procedure. Higher green and sustainable qualities were declared by suggested approaches than by earlier ones.

Utility of sustainable ratio derivative spectrophotometry for the concurrent assay of synergistic repurposed drugs for COVID-19 infections; Insilico pharmacokinetics proof

The cutting-edge combination of fluvoxamine (FVM) and ivermectin (IVM) has been presented as a proposed dosage form for the treatment of COVID-19 infections in early diagnosed patients. The main objective of this work is to develop simple, sensitive, and efficient methods for the synchronous quantification of FVM and IVM without any prior separation. Four green UV-methods were employed for the synchronous quantification, namely: Fourier functions convolution of absorption spectra, FFAS, Fourier functions convolution of derivative spectra of absorption curves, FFDS, Fourier function convolution of ratio spectra of absorption curves, FFRS and the dual-wavelength method, DWM. FFRS and DWM approaches can be able to reconcile the two components' significantly interfering spectrum presented in this commixture. Good linearity was checked in the range of 5–40, and 2.5–25 μg/mL for the FVM, and IVM, respectively. All approaches developed have been recommended in compliance with ICH principles. Furthermore, the approaches’ greenness was predestined by “National Environmental Method Index” (NEMI), “Analytical GREEnness metric (AGREE)”, the “Analytical Eco-Scale”, and the “Green Analytical Procedure Index” (GAPI). In addition, spider diagram was utilized for the assessment of the greenness index of the solvent used. Beside greenness, the sustainability of our methods was investigated using the HEXAGON tool. Continuing the constant pursuit of greenness, drug-drug interactions (DDIs) between FVM & IVM were predicted by insilico tools to ensure the safety of the suggested mixture as a preliminary step before invitro and in vivo studies. Because they were deemed sustainable, affordable, and successful, the suggested UV-methods may be used for routine quality control investigations of the indicated formulations FVM & IVM.

Development and Validation of Four Spectrophotometric Methods for Assay of Rebamipide and its Impurity: Application to Tablet Dosage Form.

Rebamipide (REB) is quinolinone derivative compound, which is used for the treatment of stomach ulcers. The development of four spectrophotometric methods for quantification of REB and its impurity and degradation product: the debenzoylated isomer of REB (DER). Method A is ratio difference spectrophotometry where 254 and 291 nm were selected for REB and 320 and 355 nm were selected for DER, allowing spectral discrimination for both. Method B is derivative ratio spectrophotometry, where the peak amplitudes of the first derivative of ratio spectra at 261 and 350.2 nm for REB and DER, respectively, are determined. Method C is a second derivative approach, which allows quantification of both REB and DER at 337 and 340 nm, respectively. Method D is mean centering of ratio spectra, where electronic absorption spectra of REB and DER were recorded and divided by a suitable divisor from DER and REB, respectively, and then the mean center is represented by the ratio spectrum so obtained. The proposed methods are simple, selective, and sensitive in the quantification of REB and DER. These methods were validated according to International Conference on Harmonization guidelines. Statistical analyses performed on the findings from the suggested methods and those obtained from reported methods revealed high accuracy and good precision. The developed and validated methods are useful for quality control assay in routine analyses. First derivative, second derivative, derivative ratio, and mean centering methods for quantification of REM and DER. These methods are useful for analysis of REB in pharmaceutical dosage form.

VALIDATED SPECTROPHOTOMETRIC METHODS FOR THE ESTIMATION OF CINNARIZINE IN BINARY MIXTURE WITH PARACETAMOL IN BULK AND TABLETS

Objectives: The aim of this work was to develop and validate new, simple, accurate, and selective spectrophotometric methods (derivative and derivative ratio spectrophotometric methods) for the determination of these drugs. These methods can be used as analytical tools in routine examination in quality control laboratories.
 Methods: The first method was derivative method in which the first derivative method (1D) for determination of PCM and the second derivative method (2D) for determination of CIN. The second method was the first derivative ratio spectrophotometric method (1DD) for determination of CIN and PCM.
 Results: In first method, the first derivative spectrum (1D) of PCM where PCM was determined by measuring the amplitude of the valley at 235 nm while CIN showed zero crossing spectrum, and the second derivative spectrum (2D) of CIN where CIN was determined by measuring the amplitude of the peak at 287.5 nm while PCM showed a zero value. In the second method, the first derivative ratio spectrophotometry (1DD) for CIN and PCM determination, where the amplitude at 290 and 291 nm, was selected for the determination of CIN and PCM, respectively.
 Conclusions: The developed methods were applied for the determination of the cited drugs in tablets containing binary drug mixture. The methods are simple and precise and can be used for routine analysis of the labeled drugs in combined dosage forms in quality control laboratories.

SIMULTANEOUS QUANTITATIVE RESOLUTION AND VALIDATION OF BINARY MIXTURE IN A PHARMACEUTICAL DOSAGE FORM BY USING A SPECTROPHOTOMETRIC SIGNAL PROCESSING TECHNIQUE

Objective: In this context, a rapid and powerful signal processing approach, a ratio-derivative spectrophotometry (RDS) method were developed for the simultaneous determination of irbesartan (IRB) and hydrochlorothiazide (HCT) in a tablet. Material and Method: The RDS method was applied to the UV spectra of the IRB and HCT. The calibration equations were obtained by measuring amplitudes at 236.3 nm for the IRB determination and at 260.0 nm for the HCT determination, respectively. The proposed method was validated by using the recovery studies, intra-day and inter-day assays and standard addition technique. Result and Discussion: This study aims to apply a rapid and powerful signal processing method to the simultaneous quantification of IRB and HCT in their synthetic mixtures and tablets. As can be seen, the UV spectra of two drugs overlapped strongly in same spectral region. Direct conventional absorbance measurements do not give expected results for the IRB-HCT tablet analysis mainly due to the spectral interference. However, in order to reach a reasonable spectral analysis outcome, we focused mainly on the application of the ratio-derivative spectra treatment to the quantitative resolution of IRB-HCT mixtures without having to a separation procedure.

Determination of Rufinamide in the Presence of 1-[(2,6-Difluorophenyl)Methyl]-1H-1,2,3-Triazole-4 Carboxylic Acid Using RP-HPLC and Derivative Ratio Methods as Stability Indicating Assays to Be Applied on Dosage Form.

Rufinamide is a triazole derivative that is structurally dissimilar to other marketed antiepileptic drugs, has been assumed a marketing authorization, by the European Union and FDA, for use as a complementary therapy for seizures associated with Lennox-Gastaut syndrome. This work is concerned with development of two methods for determination of rufinamide (RUF) in presence of 1-[(2,6-difluorophenyl)methyl]-1H-1,2,3-triazole-4 carboxylic acid as its alkaline degradation product in dosage form. The first method was capable of determing RUF in the presence of its alkaline degradation product and in dosage form. Kromasil C8 column and mobile phase consisting of acetonitrile-water (50:50, v/v) were used and UV detection at 210 nm. In the second method, first derivative ratio spectrophotometry, RUF was determined by measuring peak amplitude at 269.5 nm over 5-30 μg/mL. The linearity range of RUF was 10-90 μg/mL for HPLC method covering its therapeutic range with r2 = 0.9999. Forced degradation under alkaline conditions was carried out, the degradation product was isolated and its structure was confirmed. Both methods were validated in accordance to ICH guidelines. Statistical analysis revealed no significant difference between obtained results and reported ones. The present study is useful for therapeutic drug monitoring and routine analysis of RUF in quality control laboratories. Kinetics of the alkaline degradation of RUF was studied by following the concentration of the remaining drug until complete degradation was achieved.

Selective stability-indicating methods for the determination of clonidine hydrochloride and/or its related substance, 2,6-dichloroaniline

Three rapid, sensitive and selective analytical methods were developed for the determination of clonidine hydrochloride and its related substance: 2,6-dichloroaniline in a mixture of both. The first method depends on derivative-ratio spectrophotometry where the first derivative signals of the ratio spectra at 228.4 nm (Δλ = 2 nm) were selected to determine clonidine hydrochloride. The second method is based on measuring the first derivative response of 2,6-dichloroaniline at 300.8 nm with no interference from intact clonidine hydrochloride. In the third method, 2,6-dichloroaniline was determined via diazotization and coupling with N-(1-naphthyl) ethylenediamine to yield a colored azo dye which was measured at 498 nm. Various parameters affecting each method were studied and optimized. The proposed methods were validated according to USP guidelines concerning linearity, ranges, accuracy, precision, detection and quantification limits. The derivative-ratio spectrophotometric method was applied to the analysis of clonidine hydrochloride in tablets and the results were found in good agreement with those of the USP XXX HPLC procedure, while both the second and third methods permitted the selective analysis of 2,6-dichloroaniline in clonidine hydrochloride raw material.

DERIVATIVE UV SPECTROSCOPIC APPROACHES IN MULTICOMPONENT ANALYSIS–A REVIEW

The spectrophotometric multi-component analysis involves spectrum recording and mathematical equations. However, spectral interference poses a major limitation when mixture samples are encountered. To overcome this derivative spectrophotometry (DS) has been introduced for the resolution of overlapping peaks.
 In this review modified methods like derivative quotient spectra, double divisor ratio spectra derivative method, double divisor means centering of ratio spectra method, derivative subtraction coupled with the constant multiplication method (DS-CM), amplitude subtraction (AS), modified amplitude subtraction (MAS), amplitude factor method (P-Factor), amplitude modulation method (AM), amplitude summation method (A-Sum), simultaneous derivative ratio spectrophotometry (S1DD), derivative compensation ratio via regression equation, differential dual wavelength (D1 DWL), differential derivative ratio (D1DR), successive derivative subtraction method (SDS) and derivative transformation (DT) of derivative spectrophotometry theories and applications are reviewed.
 These methods were applied to solve different complex pharmaceuticals mixtures. These developed methods were simple and cost-effective.

A novel core-shell-based chromatographic method supported by ratio derivative spectrophotometry for the simultaneous determination of perindopril, indapamide, and amlodipine ternary mixtures

In this work, ratio spectra of the first derivative spectrophotometric and liquid chromatographic methods have been described for the first time for the simultaneous determination of perindopril (PER), indapamide (IND), and amlodipine (AML) in dosage forms. For chromatographic separations several mobile phase compositions were tested for efficient separation with the use of a new column technology related to superficially porous particles. Optimum chromatographic separation was achieved using a Kinetex C18 column (150 × role=presentation> × × \times 4.6 mm I.D. 5 μ role=presentation> μ μ \mu m) at a flow rate of 1.5 mL min − 1 role=presentation> − 1 − 1 ^{-1} . The separation was carried out at 30 ∘ role=presentation> ∘ ∘ ^{\circ} C and the diode array detector was adjusted to 215 nm. As a comparison, a spectrophotometric method depending on the first derivative of the ratio spectra was developed. The first derivative of the ratio amplitudes at 227.2 nm for PER, 269.4 nm for AML, 292.0 nm for IND were selected. The proposed methods were successfully applied for the simultaneous assay of the drug combination in pharmaceutical dosage forms and the methods were compared to each other in terms of Student t and F tests for the comparison of their accuracy and precision parameters.

Stability indicating determination of Albendazole in bulk drug and pharmaceutical dosage form by chromatographic and spectrophotometric methods

Two sensitive stability indicating methods were developed for the determination of Albendazole in bulk drug and pharmaceutical dosage form, in presence of its alkaline-degradation product without any interference. The first one was isocratic HPLC method; using Agilent Zorbax Extend C-18 (150 × 4.6 mm, 5 μ) column, ' KH2PO4 solution and acetonitrile' in the ratio of (15:85v/v) as a mobile phase with a flow rate 0.6 ml min −1 and UV-detection at 295.0 nm, where the investigated drug could be quantized in a concentration range 1.00–50.00 μgml−1 with regression coefficient (r) of 0.9989. On the other hand, the second adopted method was derivative ratio spectrophotometry; where Albendazole could be determined in a concentration range 2.00–20.00 μg ml−1 at 281.4 and at 292.6 nm-296.8 nm (Peak-to-Peak difference) with a mean percentage recovery of 100.84 and 99.88 and with regression coefficient (r) of 0.9998 and 0.9999, respectively. The utilized methods were validated according to International Conference Harmonization (ICH) guidelines and successfully applied for analysis of bulk powder and pharmaceutical dosage form. All the obtained results were statistically compared to the chromatographic reported method and no significant difference was found; indicating the accuracy, sensitivity and reproducibility of the used methods.

Resolution of overlapped spectra for the determination of ternary mixture using different and modified spectrophotometric methods

Four new spectrophotometric methods were developed, applied to resolve the overlapped spectra of a ternary mixture of [aliskiren hemifumarate (ALS)–amlodipine besylate (AM)–hydrochlorothiazide (HCT)] and to determine the three drugs in pure form and in combined dosage form. Method A depends on simultaneous determination of ALS, AM and HCT using principal component regression and partial least squares chemometric methods. In Method B, a modified isosbestic spectrophotometric method was applied for the determination of the total concentration of ALS and HCT by measuring the absorbance at 274.5nm (isosbestic point, Aiso). On the other hand, the concentration of HCT in ternary mixture with ALS and AM could be calculated without interference using first derivative spectrophotometric method by measuring the amplitude at 279nm (zero crossing of ALS and zero value of AM). Thus, the content of ALS was calculated by subtraction. Method C, double divisor first derivative ratio spectrophotometry (double divisor 1DD method), was based on that for the determination of one drug, the ratio spectra were obtained by dividing the absorption spectra of its different concentrations by the sum of the absorption spectra of the other two drugs as a double divisor. The first derivative of the obtained ratio spectra were then recorded using the appropriate smoothing factor. The amplitudes at 291nm, 380nm and 274.5nm were selected for the determination of ALS, AM and HCT in their ternary mixture, respectively. Method D was based on mean centering of ratio spectra. The mean centered values at 287, 295.5 and 269nm were recorded and used for the determination of ALS, AM and HCT, respectively. The developed methods were validated according to ICH guidelines and proved to be accurate, precise and selective. Satisfactory results were obtained by applying the proposed methods to the analysis of pharmaceutical dosage form.

Discrete Wavelet Transform-Partial Least Squares Versus Derivative Ratio Spectrophotometry for Simultaneous Determination of Chlorpheniramine Maleate and Dexamethasone in the Presence of Parabens in Pharmaceutical Dosage Form

Purpose: To compare two methods, based on different approaches, for simultaneous determination of chlorpheniramine maleate (CHP) and dexamethasone (DX) in the presence of methyl and propyl paraben in phenadone syrup.Methods: The first method used, based on univariate calibration approach, was first derivative of the ratio spectrophotometry (DD1). The second method, which is a multivariate calibration approach, was discrete wavelet transform followed by partial least squares method (DWT-PLS) which anticipated high predictive ability for the determination of both CHP and DX.Results: DD1 method failed to determine DX due to the absence of adequate zero crossing point while DWT-PLS method was successfully applied for the analysis of raw materials and the dosage form. For DD1 method, recovery of chlorpheniramine maleate in the dosage form was 100.33 ± 0.91 % while for DWT-PLS method, recovery of chlorpheniramine maleate and dexamethasone was 100.24 ± 1.21 and 99.99 ± 1.08 %, respectively. The proposed methods were validated using standard addition technique and the results compared favorably with those obtained by a reference high performance liquid chromatography (HPLC) method.Conclusion: The findings of this work show the superiority of DWT-PLS over DD1 method in solving such complex mixtures, and would thus be suitable for use in quality control (QC) laboratories and pharmaceutical industry.Keywords: Quantitative analysis, Discrete wavelet transform, First derivative of ratio spectra, Chlorpheniramine maleate, Dexamethasone

English

In this paper, ratio derivative UV spectroscopic method was developed and validated for the determination of thiamethoxam residue in tea. To estimate thiamethoxam, the amplitude of the first derivative of the corresponding ratio spectra at 258nm was used. Correlation coefficient of the calibration model was considered to be 0.9977. Besides the method was validated according to ICH guidelines by assessing the linearity, accuracy, limit of quantification, limit of detection. The results demonstrate that ratio derivative spectrophotometry is suitably applied for the detection of thiamethoxam residue in tea.

Development of normalized spectra manipulating spectrophotometric methods for simultaneous determination of Dimenhydrinate and Cinnarizine binary mixture

Simultaneous determination of Dimenhydrinate (DIM) and Cinnarizine (CIN) binary mixture with simple procedures were applied. Three ratio manipulating spectrophotometric methods were proposed. Normalized spectrum was utilized as a divisor for simultaneous determination of both drugs with minimum manipulation steps. The proposed methods were simultaneous constant center (SCC), simultaneous derivative ratio spectrophotometry (S1DD) and ratio H-point standard addition method (RHPSAM). Peak amplitudes at isoabsorptive point in ratio spectra were measured for determination of total concentrations of DIM and CIN. For subsequent determination of DIM concentration, difference between peak amplitudes at 250nm and 267nm were used in SCC. While the peak amplitude at 275nm of the first derivative ratio spectra were used in S1DD; then subtraction of DIM concentration from the total one provided the CIN concentration. The last RHPSAM was a dual wavelength method in which two calibrations were plotted at 220nm and 230nm. The coordinates of intersection point between the two calibration lines were corresponding to DIM and CIN concentrations. The proposed methods were successfully applied for combined dosage form analysis, Moreover statistical comparison between the proposed and reported spectrophotometric methods was applied.

Simultaneous determination of methocarbamol and aspirin binary mixture in their combined tablets by derivative and ratio derivative spectrophotometry

Two simple and rapid spectrophotometric methods for the simultaneous determination of methocarbamol and aspirin in their combined dosage form.

Zero crossing and ratio spectra derivative spectrophotometry for the dissolution tests of amlodipine and perindopril in their fixed dose formulations

Abstract Dissolution tests of amlodipine and perindopril from their fixed dose formulations were performed in 900 mL of phosphate buffer of pH 5.5 at 37°C using the paddle apparatus. Then, two simple and rapid derivative spectrophotometric methods were used for the quantitative measurements of amlodipine and perindopril. The first method was zero crossing first derivative spectrophotometry in which measuring of amplitudes at 253 nm for amlodipine and 229 nm for perindopril were used. The second method was ratio derivative spectrophotometry in which spectra of amlodipine over the linearity range were divided by one selected standard spectrum of perindopril and then amplitudes at 242 nm were measured. Similarly, spectra of perindopril were divided by one selected standard spectrum of amlodipine and then amplitudes at 298 nm were measured. Both of the methods were validated to meet official requirements and were demonstrated to be selective, precise and accurate. Since there is no official monograph for these drugs in binary formulations, the dissolution tests and quantification procedure presented here can be used as a quality control test for amlodipine and perindopril in respective dosage forms.

Application of derivative and derivative ratio spectrophotometry to simultaneous trace determination of rhodamine B and rhodamine 6G after dispersive liquid–liquid microextraction

Two novel methods, first derivative spectrophotometric method (1D) and first derivative ratio spectrophotometric method (1DR), have been developed for the simultaneous trace determination of rhodamine B (RhB) and rhodamine 6G (Rh6G) in food samples after dispersive liquid–liquid microextraction (DLLME). The combination of derivative spectrophotometric techniques and DLLME procedure endows the presented methods with enhanced sensitivity and selectivity. Under optimum conditions, the linear calibration curves ranged from 5 to 450ngmL−1, with the correlation coefficients (r) of 0.9997 for RhB and 0.9977 for Rh6G by 1D method, and 0.9987 for RhB and 0.9958 for Rh6G by 1DR method, respectively. The calculated limits of detection (LODs) based on the variability of the blank solutions (S/N=3 criterion) for 11 measurements were in the range of 0.48–1.93ngmL−1. The recoveries ranged from 88.1% to 111.6% (with RSD less than 4.4%) and 91.5–110.5% (with RSD less than 4.7%) for 1D and 1DR method, respectively. The influence of interfering substances such as foreign ions and food colorants which might be present in the food samples on the signals of RhB and Rh6G was examined. The developed methods have been successfully applied to the determination of RhB and Rh6G in black tea, red wine and chilli powder samples with the characteristics of simplicity, cost-effectiveness, environmental friendliness, and could be valuable for routine analysis.

Validated spectrophotometric methods for the evaluation of Oseltamivir counterfeit pharmaceutical capsules

Four rapid, reliable and economical spectrophotometric methods have been established for the quantitative determination of Oseltamivir phosphate (OST) without the interference of ascorbic acid (ASC) found in some of its counterfeit capsules. The first method involves the use of derivative spectrophotometry with the zero-crossing technique where OST was easily determined using its 1D (Δλ=3) at 219nm. The second method is based on a first-order derivative ratio spectrophotometry (1DD, Δλ=5) where 218nm was selected for its quantification, while the third method applies a more advanced spectrophotometric method based on the ratio difference spectrophotometry (RD) in which the difference in absorbance ratio was measured between 217 and 210nm. In the fourth method, difference spectrophotometric method (ΔA) is applied by subtracting absorbance at 252 from that at 263nm where the difference in absorbance was zero for ASC. The proposed methods were validated for linearity, accuracy, precision and selectivity. Synthetic mixtures of different proportions and commercial capsules were assayed by the proposed methods and the results revealed good accuracy and repeatability of the developed methods.

Simultaneous Determination of Allura Red and Ponceau 4R in Drinks with the Use of Four Derivative Spectrophotometric Methods and Comparison with High-Performance Liquid Chromatography

Four simple, rapid, sensitive, and accurate spectrophotometric methods were developed for the simultaneous determination of Allura Red (AR) and Ponceau 4R (P) without previous chemical separation. The first method, derivative spectrophotometry, depends on first derivative spectrophotometry with zero-crossing and peak-to-base measurement. The second method, derivative ratio spectrophotometry, uses the first derivative of the ratio spectra. The ratio spectra are obtained by dividing the absorption spectra of a binary mixture by that of one of the components. The third method, differential derivative spectrophotometry, is based on the measurement of the difference absorptivities derivatized in the first order of a sample extract in 0.1 M NaOH relative to that of an equimolar solution in 0.1 M HCl. The fourth method, based on the compensation technique, is presented for the derivative spectrophotometric determination of binary mixtures with overlapping spectra by using ratios of the derivative maximum or minimum; the exact compensation of either component in the mixture can be achieved, followed by its determination. All the proposed methods were successfully applied to the determination of the colorants in their laboratory mixtures and granulated drinks without any interference by the ingredients. AR and P showed good linearity, with regression coefficients of 0.9994-0.9999. The LOD and LOQ values ranged from 0.059 to 0.102 and 0.198 to 0.341 microg/mL, respectively. The intraday and interday precision tests produced good RSD values (<1.37%); recoveries ranged from 98.75 to 100.37% for all four methods. The common ingredients and additives did not interfere in the AR and P determination. The results of the proposed methods were statistically compared with the results of an HPLC method given in the literature (Nordic Committee on Food Analysis; NMKL 130) at the 95% confidence level by Student's test and the variance ratio F-test. No statistically significant difference was found among these methods.

Riluzole: Validation of Stability-Indicating HPLC, D1 and DD1 Spectrophotometric Assays

A stability-indicating reversed-phase high-performance liquid chromatographic assay procedure has been developed and validated for riluzole in the presence of alkaline and oxidative degradation products. The liquid chromatographic separation was achieved and compared isocratically on C18 Zorbax ODS and Poroshell 120 EC-C18 columns by using a mobile phase containing methanol-water, pH = 3.10 (70:30, v/v), at a flow rate of 1 mL/min and ultraviolet detection at 264 nm. The method was linear over the concentration ranges of 20-200 µg/mL (r = 0.9997) and 10-200 µg/mL (r = 0.9995). The limit of detection and quantitation for the two columns were 2 and 6 µg/mL and 1 and 3 µg/mL, respectively. Moreover, spectrophotometric methods were applied for the determination of riluzole in the presence of its oxidative degradation products by using first derivative spectrophotometry at 252.5 and 275.0 nm. The method was linear over the concentration range of 1-20 µg/mL (r = 0.9995 and 0.9996) at the studied wavelengths, with limits of detection and quantitation of 0.1 and 0.3 µg/mL. In addition, the first derivative ratio spectrophotometry (DD1) method was applied for the determination of riluzole in the presence of its alkaline degradation product at 252.0, 278.5 and 306.3 nm by using 100 µg/mL of alkaline degraded riluzole as a divisor; riluzole was additionally determined in the presence of its hydrogen peroxide oxidative degradation products at 252.5, 275.0 and 305.0 nm by using 200 µg/mL of oxidative degraded riluzole as a divisor. The DD1 method was linear over the concentration range of 1-20 µg/mL (r = 0.9996, 0.9995 and 0.9996 for the alkaline degradation product at the three studied wavelengths, respectively; and r = 0.9995, 0.9996 and 0.9995 for the oxidative degradation product at the three studied wavelengths, respectively), with limits of detection and quantitation of 0.1 and 0.3 µg/mL for both alkaline and oxidative degradation products. The two studied chromatographic and spectrophotometric methods were comparable and display the required accuracy, selectivity, sensitivity and precision to assay riluzole in bulk and pharmaceutical dosage forms. Degradation products resulting from the stress studies did not interfere with the detection of riluzole, which indicates that these are stability-indicating assays.