SPECTROPHOTOMETRIC ESTIMATION OF TOLPERISONE HYDROCHLORIDE AND DICLOFENAC SODIUM IN SYNTHETIC MIXTURE BY DUAL WAVELENGTH METHOD

ABOUT AUTHORS:
Hiral H. Patel*, Paresh U. Patel,
Department of Pharmaceutical Analysis, Center for Health and Science Studies,
Ganpat University, Ganpat Vidyanagar – 384012,
Mehsana, Gujarat, India.
*patel.hiral2210@gmail.com

ABSTRACT
This method describes simple, sensitive, rapid, accurate, precise and economical derivative spectroscopic methodfor the simultaneous determination of tolperisone hydrochloride (TOL) and diclofenac sodium (DIC) in bulk and synthetic mixture. In this study, dual wavelength spectroscopic method was used for simultaneous determination of tolperisone hydrochloride and diclofenac sodium using the absorbance difference at two wavelengths. The absorbance differences of 257 nm and 306.20 nm were selected for the estimation of TOL and the absorbance differences of 243.40 nm and 265.40 nm were selected for estimation of DIC. The method was found to be linear (r2>0.999) in the range of 2- 18 μg/ml for tolperisone hydrochloride. The linear correlation was obtained (r2>0.997) in the range of 2- 18 μg/ml for diclofenac sodium. The limit of determination was 0.66 and 0.27 μg/ml for tolperisone hydrochloride and diclofenac sodium respectively. The limit of quantification was 2.00 and 0.83 μg/ml. The method was successfully applied for simultaneous determination of tolperisone hydrochloride and diclofenac sodium in binary mixture.

REFERENCE ID: PHARMATUTOR-ART-1696

INTRODUCTION
Tolperisone (TOL) is chemically 2-methyl-1-(4-methylphenyl)-3-(1-piperidyl) propan-1-one (Figure 1) is a well known antispasmodic drug1. It is official in Japanese Pharmacopoeia (JP). JP2 describe potentiometry method for its estimation. Literature survey reveals HPLC3 and UV4 method for estimation of TOL alone. Literature survey also reveals HPLC5 and UV spectrophotometry6 methods for determination of TOL with other drugs in combination. Diclofenac sodium (DIC) is chemically 2-[2,6diclohlorophenylamino] benzene acetic acid sodium salt7 (Figure 2). Diclofenac sodium (DIC) is official in Indian Pharmacopoeia (IP)and British Pharmacopoeia (BP). IP8 and BP9 describe liquid chromatography method for its estimation. Literature survey reveals HPLC10, 11 and UV12 method for determination of DIC alone. Literature survey also reveals HPLC13, 14, 15, UV spectrophotometry16 and HPTLC17 method for the determination of DIC with other drugs combination. The combination of these two drugs is not official in any pharmacopoeia; hence no official method is available for the simultaneous estimation of TOL and DIC in their combined synthetic mixture or dosage forms. Literature survey does not reveal any simple spectrophotometric method for simultaneous estimation of TOL and DIC in synthetic mixture or combined dosage forms. The present communication describes simple, sensitive, rapid, accurate, precise and cost effective spectrophotometric method based on derivative spectroscopic method for simultaneous estimation of both drugs in bulk and combined synthetic mixture.

MATERIALS AND METHODS

Apparatus
A shimadzu model 1700 (Japan) double beam UV/Visible spectrophotometer with spectral width of 2 nm, wavelength accuracy of 0.5 nm and a pair of 10 mm matched quartz cell was used to measure absorbance of all the solutions. Spectra were automatically obtained by UV-Probe system software. A Sartorius CP224S analytical balance (Gottingen, Germany), an ultrasonic bath (Frontline FS 4, Mumbai, India) was used in the study.

Reagents and materials
TOL and DIC bulk powder was kindly gifted by Torrent Research Centre, Gandhinagar, India and Acme Pharmaceuticals Ltd. Ahmadabad, Mehsana, Gujarat, India, respectively. Methanol (AR Grade, S. D. Fine Chemicals Ltd., Mumbai, India) and Whatman filter paper no. 41 (Millipore, USA) were used in the study.

Preparation of standard stock solutions
An accurately weighed standard TOL and DIC powder (10 mg) were weighed and transferred to 100 ml separate volumetric flasks and dissolved in methanol. The flasks were shaken and volumes were made up to mark with methanol to give a solution containing 100 μg/ml of each TOL and DIC.

Selection of wavelength
The standard solutions of TOL (10 µg/ml) and DIC (10 µg/ml) were scanned separately in the UV range of 200-400 nm. It appeared that at 257 nm and 306.20 nm DIC shows same absorbance so the absorbance differences of these wavelengths were selected for the estimation of TOL. While at 243.40 nm and 265.40 nm TOL shows same absorbance so the absorbance differences of these wavelengths were selected for estimation of DIC.

Validation of the proposed method
The proposed method was validated according to the International Conference on Harmonization (ICH) guidelines18.

Linearity (calibration curve)
To check linearity of the method, working standard solution having concentration in range of 2-18 µg/ml for TOL and 2-18 µg/ml for DIC were prepared from the standard stock solutions of both drugs. Aliquots of standard solution of TOL (0.2, 0.4, 0.6, 0.8, 1.0, 1.4, 1.8 ml) and DIC (0.2, 0.4, 0.6, 0.8, 1.0, 1.4, 1.8 ml) of standard stock solutions of both drug were transferred separately to a series of 10 ml volumetric flasks and diluted to mark with methanol, and the absorbance difference of 257 nm and 306.20 nm was measured for TOL and the absorbance difference of 243.40 nm and 265.40 nm was measured for DIC. The calibration curves were constructed by plotting absorbance difference vs. concentration.

Method precision (repeatability)
The precision of the instrument was checked by repeated scanning and measuring the absorbance of solution of (n = 6) TOLand DIC (8 µg/ml) without changing the parameters of First Derivative Method.

Intermediate precision (reproducibility)
The intraday and interday precision of the proposed method was determined by analyzing the corresponding responses 3 times on the same day and on 3 different days over a period of 1 week for 3 different concentrations of standard solutions of TOL and DIC (4, 8, 12 µg/ml for TOL and 4, 8, 12 µg/ml for DIC). The result was reported in terms of relative standard deviation (% RSD).

Accuracy (recovery study)
The accuracy of the method was determined by calculating recovery of TOL and DIC by the standard addition method. Known amounts of standard solutions of TOL and DIC were added at 50, 100 and 150 % level to prequantified sample solutions of TOL and DIC (4 µg/ml for TOL and 4 µg/ml for DIC). The amounts of TOL and DIC were estimated by applying obtained values to the regression equation of the calibration curve.

Limit of detection and Limit of quantification
The limit of detection (LOD) and the limit of quantification (LOQ) of the drug were derived by calculating the signal-to-noise ratio (S/N, i.e., 3.3 for LOD and 10 for LOQ) using the following equations designated by International Conference on Harmonization (ICH) guidelines18.

LOD = 3.3 × σ/S

LOQ = 10 × σ/S

Where, σ = the standard deviation of the response and S = slope of the calibration curve

Analysis of synthetic mixture
After proper dilution of prepared solution of synthetic mixture the absorbance of the sample solution was measured at 257 nm and 306.20 nm for quantitation of TOL and at 243.40 nm and 265.40 nm for quantitation of DIC, respectively. The amounts of the TOL and DIC present in the sample solution were calculated by fitting the responses into the regression equation for TOL and DIC in the First Derivative Method.

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