ОПТИКА И СПЕКТРОСКОПИЯ, 2015, том 118, № 6, с. 1036-1039
ГЕОМЕТРИЧЕСКАЯ И ПРИКЛАДНАЯ ОПТИКА
УДК 535.3+535.8
FIRST ORDER DERIVATIVE SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF BENIDIPINE HYDROCHLORIDE PHARMACEUTICAL PREPARATIONS AND FORCED DEGRADATION STUDY © 2015 г. Ayga Karasakal
Department of Chemistry, Faculty of Science and Letters, Namik Kemal University, Tekirdag, Turkey
E-mail: aycakarasakal@yahoo.com Received July 21, 2014
A simple and rapid first order derivative spectrophotometric method was developed for the determination of benidipine hydrochloride in pure form and pharmaceutical preparations. For the first derivative spectrophotometric method, the distances between two extremum values (peak-to-peak amplitudes), 230.2/241.5 nm. The proposed method was validated according to the ICH guidelines with respect to linearity, limit of detection, limit of quantification, accuracy, precision (intra- and inter-day) and recovery were evaluated. The linearity of the method was in the range of 0.2-2.0 ^g/mL. Limits of detection and quantification were 0.58 and 1.73 ^g/mL, respectively. The proposed method was successfully applied to the analysis of pharmaceutical preparations. In addition, forced degradation studies were performed on the benidipine hydrochloride drag subtance. The drug substance was exposed to the stress conditions of hydrolysis (acid and base).
DOI: 10.7868/S0030403415060033
INTRODUCTION
Benidipine hydrochloride (BEN) is a dihydropyri-dine analogue calcium-channel blocker, which has been used clinically as an antihypertensive and antianginal agent and chemically named as O5-methyl O3-[(3R) -l- (phenylmethyl)pip eridin- 3 -yl] 2,6-di-methyl-4-(3-nitrophenyl)-1,4-dihydropyridine-3,5-di-carboxylate [1, 2] (Fig. l).
Various analytical procedures have been reported for the determination of BEN. They include cyclic voltammetry, liquid chromatography [3], tandem mass spectrometry, capillary column gas chromatog-raphy [4], negative ion chemical ionization mass spectrometry [5] and spectrophotometric methods [6].
H
Fig. l. Benidipine chemical formula.
The UV-spectrophotometric technique is widely employed in pharmaceutical analysis [7—11].
The aim of this study is to develop a simple, sensitive and validated, first order derivative spectrophoto-metric method for the determination of BEN. In this work, rapid, environmentally acceptable and inexpensive, first order derivative spectrophotometric method was developed for the determination of BEN in pure and pharmaceutical preparations. Force degradation studies were performed on the placebo and drug products to show the stability-indicating nature of the method. These studies were performed in accordance with established ICH guidelines [12, 13].
EXPERIMENTAL
Reagents and Chemicals
BEN was kindly supplied from Lusochimica (Italy). Coniel tablets (4 mg) were purchased from a local pharmacy. All solvents were of analytical reagent grade. The stock and standard solutions were stored at +4°C.
Instrumentation
A double-beam Shimadzu 2600 UV/Vis Spectrophotometer with 1.00 cm quartz cells was used under the following operating conditions: scan range 200—
Fig. 2. The absorption spectrums of BEN at various concentrations (0.2, 0.4, 0.5, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8 and 2.0 pg/mL).
Abs. 0.178
0.150
0.100
0.050
450
450 nm, slith width 2 nm and derivation interval (AA) 2 nm were used.
Solutions
Stock solutions of BEN were prepared at a concentration of 0.1 mg/mL in methanol and kept at +4°C. Working standard solutions were daily prepared by diluting stock solutions at the concentrations of 0.2— 2 ^g/mL in methanol. The original UV (zero-order), first-order, second-order, third and fourth derivative spectrum of standard BEN solution of 100 ^g/mL was analysed. First order derivative spectrum was selected.
Preparation of Tablet Solution
Ten tablets of BEN were totally weighed and powdered. An amount of this powder corresponding to one tablet BEN content was weighed in to a 100 mL volumetric flask, and the flask was sonicated for 30 min. The flask was filled to volume with methanol. The sample solution (0.1 mg/mL) obtained by dilution of supernatant was used to set up the concentrations in the range of calibration studies. The assays of BEN content was completed as described under "General procedure".
General Method
UV-derivative spectrophotometry method. The
standard solutions were prepared by dilution of the working standard solution with methanol to reach
concentration ranges of 0.2—2.0 ^g/mL. The distances between two extremum values (peak-to-peak amplitudes), 230.2/241.5 nm, were measured in the first derivative (dA/dA) spectra of standard solutions. These wavelengths were selected depending on the maximum values obtained.
Forced Degradation Studies
Acid degradation study. A stock solution containing 100 mg BEN in 80 mL 0.1N HC1 was refluxed at 70°C for 1 hour to facilitate acid degradation of BEN. The flask was filled to 100 mL with methanol. This solution was diluted to 10 ^g/mL and was used by diluting from this solution for forced degradation to provide an indication of the stability-indicating property and specificity of the proposed method. In degradation study, the first order derivative spectrum of the BEN was measured.
Basic degradation study. A stock solution containing 100 mg BEN in 80 mL 0.1N NaOH was refluxed at 70°C for 1 hour to facilitate acid degradation of BEN. The flask was filled to 100 mL with methanol. This solution was diluted to 10 ^g/mL and was used by diluting from this solution for forced degradation to provide an indication of the stability-indicating property and specificity of the proposed method. In degradation study, the first order derivative spectrum of the BEN was measured.
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KARASAKAL
dA/dX 0.003
-0.005
-0.010
dA/dX 0.005
-0.005
-0.010 -
200
250
300
350
400 450
X, nm
200 250 300 350 400 450
X, nm
Fig. 3. First order derivative spectrum (1.2 ^g/mL) (AX = = 2 mn).
Fig. 5. First order derivative spectrum (3 ^g/mL) (AX = = 2 nm).
0
dA/dX
_i_i_i_i_i
200 250 300 350 400 450
X, nm
Fig. 4. First order derivative spectrum of 3 ^g/mL BEN degraded with acidic degradation (AX = 2 nm).
RESULTS AND DISCUSSION
UV absorption spectra. UV absorption spectrums of BEN showed maximum absorbance at 357 nm (Fig. 2).
Derivative Method
In this study to obtain more sensitive results, the first, second, third, and fourth derivative spectra of
BEN was achieved and then it was determined that first derivative was the best (Fig. 3).
The distance between two extremum values (peak to peak amplitudes), 230.2/241.5 were measured in the first derivative 1D spectra of standart solutions. These wavelenghs were selected depending on the maximum values obtained. Calibration curves were constructed by plotting 1D values against concentrations.
Pharmaceutical Application
The proposed method was successfully applied to pharmaceutical preparation. The determination of BEN tablets, Coniel 4 mg were analyzed by the utilizing method. The recoveries was found to be 101.0% ± 3.24%.
Forced Degradation Product
Acid degradation. The acid degradation was performed by refluxing with 0.1 N HC1 at 70°C for 1 h. First order derivative spectrums of 3 ^g/mL BEN degraded with acidic degradation and 3 ^g/mL BEN (AX = 2 nm) are shown in Figs. 4 and 5, respectively.
The percentage decomposition of degraded BEN was calculated. The results are shown in Table 1.
Basic degradation. The basic degradation was performed by refluxing with 0.1 N NaOH at 70°C for 1 h. BEN degraded with basic degradation was diluted to 10 ^g/mL and it was observed degraded BEN was not decomposition from its first order derivative spectrum.
Method validation. Method validation was performed by following the International Conference on Harmonization (ICH) guidelines [13] for analytical method validation.
Table 1. Percent of decomposed of degraded BEN
Percent of Concentration of Method of
decomposed, % BEN, |ig/mL degradation
10 3 Acidic degradation
Not observed 3 Basic degradation
Table 2. First derivative spectrophotometric determination of BEN
BEN
Beer's law range 0.2-2 |g/mL
LOD 0.58 |g/mL
LOQ 1.73 |g/mL
Regression equation 4.0644x + 0.2489
Slope (a) 4.0644
Intercept 0.2489
Correlation coefficient (r) 0.9908
Linearity. Calibration curves were constructed by plotting dA/d"k against concentrations of BEN. Linear relationships were observed over the concentration ranges of 0.2—2.0 ^g/mL.
Linearity of the calibration graph and adherence of the method to Beer's law were validated by high value of the correlation coefficient and (r2 = 0.9908) for standart solutions. The regression equation, slope, intercept an correlation coefficient were given in Table 2.
LOD (the limit of detection) and LOQ (the limit of quantitation). The LOD and LOQ of BEN using the proposed method were determined using calibration standards. LOD and LOQ were calculated to be 3.3g/S and 10g/S, respectively, where S is the slope of the calibration curve and g is the standard deviation of the intercept of the regression equation. LOD and LOQ values were calculated as 0.58 and 1.73 ^g/mL for BEN.
Precision and accuracy. BEN was assayed at three concentration levels, as described under the general analytical procedure. Assays were repeated three times within the same day to determine the inter-day precision and three times on three different days to determine the interlay precision of the method. Precision and accuracy of the method was expressed by relative standard deviation (RSD %) and relative mean error (RME %), respectively. The RME (%) and RSD (%) were found to be 5% and 0.11% indicate the high accuracy and precision of the first order derivative spectrophotometric method.
Recovery. The recovery study was performed by adding known amounts of the compounds studied to a known concentration of the commercial pharmaceutical tablets (standard additio
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