Pharmaspec-1700 Ultraviolet-Visible spectrophotometer (double. Digisun model DI-707 ph meter was used for all the ph

Transcription

1 EXPERIMENTAL Instruments Pharmaspec-1700 Ultraviolet-Visible spectrophotometer (double beam) was used for all spectral measurements. Digisun model DI-707 ph meter was used for all the ph measurements. Chemicals and Reagents: All the chemicals used were of analytical grade. 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH): was prepared by dissolving 100 mg of MBTH in 50 ml of distilled water. Ferric Chloride (FeCl3) (0.3 % w/v): was prepared by dissolving 300 mg of ferric chloride hexahydrate in 100 ml of distilled water. 1, 2 Naphthoquinone Sulphonic acid (NQS) (0.5% w/v): was prepared by dissolving 500 mg of NQS in 100 ml of distilled water. Sodium Hydroxide (NaOH) (2 % w/v): was prepared by dissolving 2 gms of NaOH in 100 ml of distilled water. PROCEDURE: Preparation of standard drug solution: Method BCT1: A standard drug solution of bicalutamide was prepared by dissolving 100 mg of drug in 100 ml of methanol in a standard volumetric flask to obtain a stock solution of 1 mg/ml.

2 105 Method BCT2: A volume of 10 ml of 1 mg/ml solution was further diluted to 100 ml with methanol to get 100 µg/ml working standard. Preparation of sample solution: A quantity of the powder from tablets equivalent to 10 mg of drug was dissolved in 10 ml methanol, filtered and analyzed by taking an aliquot and treated as per the procedure for standard. For Bulk Drug Samples Method BCT1: Aliquots of standard drug solution ( ml) were transferred into series of 10 ml graduated test tubes, 2 ml of ferric chloride and 1 ml of MBTH were added to each test tube, mixed well and volume was made upto 10 ml with methanol. The absorbance of resulting solution was measured at 630 nm against reagent blank prepared simultaneously and a linear graph was obtained. The amount of bicalutamide present in the sample solution was computed from its calibration curve. Method BCT2: Aliquots of standard drug solution ( ml) were transferred into series of 10 ml graduated test tubes, 0.5 ml of NQS and 2 ml of NaOH were added to each test tube, mixed well and volume was made upto 10 ml with methanol. The absorbance of resulting solution was measured at 453 nm against reagent blank prepared simultaneously and a linear graph was obtained. The

3 106 amount of bicalutamide present in the sample solution was computed from its calibration curve. Analysis of Formulations: Method BCT1: A volume of 1 ml of the sample solution was transferred into 10 ml graduated test tube, 2 ml of ferric chloride and 1 ml of MBTH were added to the test tube, mixed well and volume was made up to 10 ml with methanol. The absorbance of resulting solution was measured at 630 nm against reagent blank prepared simultaneously. Method BCT2: A volume of 1 ml of the sample solution was transferred into 10 ml graduated test tube, 0.5 ml of NQS and 2 ml of NaOH were added to the test tube, mixed well and volume was made up to 10 ml with methanol. The absorbance of resulting solution was measured at 453 nm against reagent blank prepared simultaneously. 3.3 RESULTS AND DISCUSSION Analytical Data and Method Validation Optimization of parameters for Methods BCT1 and BCT2 The optimum conditions were established by changing one parameter while fixing the other parameters and noting the effect on absorbance of chromogen. Bicalutamide has a secondary amino group in the molecular structure making it possible to undergo oxidative coupling of the drug with

4 107 MBTH in ferric chloride solution in method BCT1 and method BCT2 was based on reaction with NQS in sodium hydroxide. The effect of temperature of the reaction, quantity, concentration and order of addition of various reagents were studied, optimized after several experiments with respect to maximum sensitivity, color stability, adherence to Beer s law and other optimum conditions are incorporated in the procedure. Optimum conditions established for both the methods are presented in table 3.3 (Method BCT1) and table 3.4 (Method BCT2) respectively.

5 108 TABLE 3.3: OPTIMUM CONDITIONS ESTABLISHED FOR METHOD BCT1 Parameter Volume of 0.3% w/v ferric chloride solution required for oxidation Volume and strength of MBTH solution Optimum Range Conditions In The Methods Remarks 1-2 ml 2 ml Addition of less than 2ml results in low absorbance particularly with high concentrations of Beer s law limits. Addition of more than 2 ml results in high blank value. 1-2 ml 1 ml Optimum strength and volume of MBTH solution was found to be 0.2% w/v and 1 ml respectively. Other concentrations did not favor optimum color development.

6 109 Time and temperature required for oxidation Stability after complete color development 5-15 min at temp 28± 5 0 C 5 min at room temp(29 0 C) Change of time and temperature beyond optimum limits produced erratic results. 40 min >40 min Product formed is stable for sufficient period of time to complete analysis. TABLE 3.4: OPTIMUM CONDITIONS ESTABLISHED FOR METHOD BCT2 Parameter Volume of 2% NaOH solution required Optimum Range Conditions In The Methods Remarks 1-2 ml 2 ml Addition of less than 2 ml results in low absorbance particularly with high concentrations of Beer s law limits. Addition of more than 2 ml results in high blank value.

7 110 Volume and strength of NQS solution Order of addition of reagents NQS and NaOH Time and temperature required for color development Stability after complete color development 1-2 ml 0.5 ml Optimum strength and volume of NQS solution was found to be 0.5% w/v and 0.5 ml respectively. Other concentrations did not favor optimum color development. Addition of NaOH solution before the addition of NQS did not favor color development min at 5 min at room Change of time and temp 28± 5 0 C temp(29 0 C) temperature beyond optimum limits produced erratic results. 40 min >40 min Product formed is stable for sufficient period of time to complete analysis. Optical Characteristics Absorption Maximum Absorption spectra of bicalutamide for methods BCT1 and BCT2 were shown in figures 3.2 and 3.3

8 Absorbance Absorbance 111 Aborption Spectrum Of BCT with MBTH Chromogen vs MBTH, MBTH 0.5% W/V in distilled Water, BCT-500 µg/ml Reagent Blank vs Distilled Water Wavelength (nm) Fig 3.2 Absorption Spectrum of Bicalutamide with MBTH and FeCl3 Absorption Spectrum Of BCT with NQS Cmromogen vs NQS,NQS-0.5% w/v in distilled Water,BCT-20 µg/ml Reagent Blank vs Distilled Water Wavelength (nm) Fig 3.3 Absorption Spectrum of Bicalutamide with NQS

9 112 Linearity By using the method of least squares regression analysis was performed to evaluate the slope (m), intercept (b) and correlation coefficient (r) was computed from various concentrations and the results are presented in Tables 3.5 (BCT1) and 3.6 (BCT2).The graph showed negligible intercept as described by the regression equation y = mx + b where y is the absorbance and x is the concentration in µg/ml.calibration curves for methods BCT1 and BCT2 were shown in figures 3.4 and 3.5.

10 Absorbance 113 Table 3.5 Linearity data for BCT1 Conc µg/ml Absorbance Calibration Curve of BCT with MBTH y = x R 2 = Concentration in µg/ml Fig 3.4 Calibration Curve of Bicalutamide with MBTH and FeCl3

11 Absorbance 114 Table 3.6 Linearity data for BCT2 Conc µg/ml Absorbance Calibration Curve of BCT with NQS y = x R 2 = Concentration in µg/ml Fig 3.5 Calibration Curve of Bicalutamide with NQS

12 115 The optical characteristics such as molar absorptivity, Beer s law limits, absorption maxima and Sandell s sensitivity are presented in Table 3.7. Table 3.7: Optical characteristics and precision of the methods S. NO Parameter Method BCT1 Method BCT2 01 λ max (nm) Beer s law range (μg/ml) 03 Molar extinction coefficient(l.mole -1 cm -1 ) 04 Sandell s sensitivity (μg/cm 2 /0.001) 05 Regression equation (y = mx + b) * Slope (m) Intercept (b) x x Correlation coefficient (r) 07 Precision (%Relative Standard Deviation) 08 Standard Error Of Mean * y = mx + b, where y is the absorbance unit and x is the concentration in µg/ml.

13 116 Accuracy and Recovery Commercially available tablets of bicalutamide (Table 3.8) were analyzed by the proposed methods and as additional check on the accuracy of the method, recovery experiments were also conducted by spiking known amounts of pure drug in preanalysed formulation and the recovery was calculated in each of the case using the regression line equation developed under the Linearity experiment. Assay results of the proposed methods were compared with that of reference method and statistically evaluated using one-way ANOVA with post-test followed by Dunnett multiple comparison test. The means of the proposed methods are not significantly different from that of reference method (P > 0.05). The assay and accuracy results were presented in Table 3.9. The interference studies indicated the common additives and excipients present in formulations did not interfere with the proposed methods.

14 117 Table 3.8: Commercially Available Formulations of Bicalutamide Generic Name Proprietary Name Dosage Form Content Calutide, Cipla Tablets 50 mg Bicalutamide Biprosta,Alkem(Cytomed) Tablets 50 mg Caludec,Samarth Tablets 50 mg Utamide,Intas (Arron) Tablets 50 mg Table 3.9: Evaluation of Bicalutamide in pharmaceutical dosage forms (n=6) Sample a Labelled Amount (mg) Amount obtained (mg) b Proposed method d Method BCT1 Method BCT2 Reference method 101 UV Percentage Recovery b,c Method BCT1 Method BCT2 T ± ± ± ± ±0.01 T ± ± ± ± ±0.05 a - T1 and T2 are the tablets from different batches (Calutide, Cipla, Mumbai). b Mean ± SD of 6 determinations. c 20 mg of pure drug was added and recovered. For both the samples T1 and T2 One-way ANOVA with post-test followed by Dunnett multiple comparison test was performed. The results showed that P > 0.05 and the means of the proposed methods are not significantly different from that of reference method.

15 Chemistry of the colored species formed Method BCT1 Bicalutamide has a secondary amino group in the molecular structure making it possible to undergo oxidative coupling of the drug with MBTH in ferric chloride solution in method C Under the reaction conditions, MBTH loses two electrons and one proton on oxidation forming the electrophilic intermediate which has been postulated to be the active coupling species. The intermediate reacts with amine by electrophilic attack on the aromatic ring of the amine and the resulting intermediate is spontaneously oxidized with an oxidant to form the colored species via oxidative coupling mechanism.it is represented in proposed scheme 3.1 N S N NH2 + oxidant -2e, -H + N S N N+H CH3 MBTH COLOURED PRODUCT +ANALYTE CH3 S Proposed Scheme 3.1 N + CH3 N NH

16 119 Method BCT2 The method is based on the formation of a coloured derivative between bicalutamide and 1,2-naphthoquinone-4- sulphonic acid sodium salt (NQS). The reaction between bicalutamide and NQS (Proposed Scheme 3.2) is a simple condensation reaction with the elimination of NaHSO Proposed Scheme Conclusion The proposed visible spectrophotometric methods enable quantitative determination of bicalutamide in bulk drug samples and tablets. Efficient visible spectrophotometric detection at the respective absorption maxima enabled determination with no interference from the excipients. The calibration curves were linear over a concentration range from µg/ml for method BCT1 and µg/ml for method BCT2. The relative standard deviation s (R.S.D.) were less

17 120 than 1% and average recovery was above 99.83%. The proposed methods are fast, sensitive, precise, accurate, and efficient and can be used in for analysis in quality control laboratories.