Simultaneous determination of mebeverine hydrochloride and chlordiazepoxide in their binary mixture using novel univariate spectrophotometric methods via different manipulation pathways

Highlights

• Novel spectrum addition technique was used as a novel sample enrichment technique

• Novel approach namely induced amplitude modulation was applied

• Can be used for simultaneous analysis of binary mixtures with a high variety in absorptivities or concentrations without preliminary separation.

• Accurate and precise methods and could be easily applied in QC labs.

Abstract

Smart, sensitive, simple and accurate spectrophotometric methods were developed and validated for the quantitative determination of a binary mixture of mebeverine hydrochloride (MVH) and chlordiazepoxide (CDZ) without prior separation steps via different manipulating pathways. These pathways were applied either on zero order absorption spectra namely, absorbance subtraction (AS) or based on the recovered zero order absorption spectra via a decoding technique namely, derivative transformation (DT) or via ratio spectra namely, ratio subtraction (RS) coupled with extended ratio subtraction (EXRS), spectrum subtraction (SS), constant multiplication (CM) and constant value (CV) methods. The manipulation steps applied on the ratio spectra are namely, ratio difference (RD) and amplitude modulation (AM) methods or applying a derivative to these ratio spectra namely, derivative ratio (DD¹) or second derivative (D²). Finally, the pathway based on the ratio spectra of derivative spectra is namely, derivative subtraction (DS). The specificity of the developed methods was investigated by analyzing the laboratory mixtures and was successfully applied for their combined dosage form. The proposed methods were validated according to ICH guidelines. These methods exhibited linearity in the range of 2–28 μg/mL for mebeverine hydrochloride and 1–12 μg/mL for chlordiazepoxide. The obtained results were statistically compared with those of the official methods using Student t-test, F-test, and one way ANOVA, showing no significant difference with respect to accuracy and precision.

Introduction

Mebeverine hydrochloride (MVH), 4-[ethyl-[1-(4-methoxyphenyl)propan-2-yl]amino]butyl3,4-dimethoxybenzoate hydrochloride (Fig. 1a) is a musculotropic antispasmodic drug without anticholinergic side-effects. It has a major therapeutic role in the treatment of irritable bowel syndrome (IBS). MVH is also indicated for treatment of gastrointestinal spasm secondary to organic disorder [1]. Chlordiazepoxide (CDZ), 7-chloro-2-methylamino-5-phenyl-3H-1, 4-benzodiazepine-4-oxide (Fig. 1b) was the first benzodiazepine to be synthesized. CDZ has amnestic, anticonvulsant, anxiolytic, hypnotic and skeletal muscle relaxant properties as it inhibits monosynaptic and polysynaptic reflexes by acting as inhibitory neutral transmitters or by blocking excitatory synaptic transmission [2]. Both drugs have been co-formulated and widely used to reduce irritable bowel syndrome, spastic colon and relief of gastrointestinal manifestation of anxiety and tension of GIT.

Many methods have been reported for the quantitative determination of CDZ based on spectrophotometry [3], [4], [5], electrochemical methods [6], [7] and chromatographic method [8]. Several analytical procedures have been reported for the quantitative determination of MVH including spectrophotometric methods [9], [10], electrochemical methods [11], [12] and chromatographic methods [13], [14], [15], [16].

Few spectrophotometric methods [17] and HPLC methods [18], [19] were described for the simultaneous determination of both drugs in solid dosage forms.

The main problem of spectrophotometric multicomponent analysis is the simultaneous determination of two or more compounds in the same mixtures with overlapping spectra without preliminary separation. Several univariate spectrophotometric methods have been used for resolving mixtures with overlapping spectra such as H-point standard addition method for binary [20] and ternary [21] mixtures, the ratio derivative spectrophotometry for binary [22] and derivative ratio spectra-zero crossing for ternary mixtures [23], [24], and the double divisor-ratio spectra derivative method for the determination of ternary mixtures [25], [26]. Multivariate methods were also reported as partial least squares regression [27], principal component regression [25] and multiple linear regression analysis [28].

Univariate methods were based on different manipulation pathways which could be used for the determination of the two cited drugs in their binary mixtures. These pathways include the direct measurement of the absorbance of the scanned zero order absorption spectrum or the recovered one which was obtained after successive manipulation steps. The second pathway was based on the measurement of the amplitude of the ratio spectrum which was obtained by the division of the zero order absorption spectra as well as the amplitude of the derivative spectrum or their ratio spectra.

The aim of this work is to develop and compare recently developed univariate spectrophotometric methods with different manipulation pathways namely, DS–CM [29], DT [30] or methods for resolving the binary mixtures with spectral overlapping problems without preliminary separation using unified regression equation {AS, AM} [31], [32], [33] and the well-established spectrophotometric methods (RS [34], EXRS [35], SS [36], {CM, CV} [37], RD [35], DD¹ [38], D² [39]) in terms of specificity and validation. Absorbance subtraction (AS) and amplitude modulation (AM) methods are considered as a new approach to the isosbestic point method either in zero order absorption spectrum namely, isoabsorptive point [40], [41] or in the ratio spectrum [42] at which the total concentration of both components in the mixture was calculated, by using smart mathematical techniques utilizing the absorption factor [43], [44] in zero order absorption spectra or constants in the ratio spectra which could be adapted to isosbestic point analysis for separate quantitative estimation of each drug in their mixture using unified regression equation. The proposed methods are very simple, accurate, precise and do not require any sophisticated apparatus or computer programs.