Validation of New Spectrophotometric Methods for the Determination of Fluvoxamine as Maleate in Pharmaceutical Formulations
Medikondu Kishore*, A. Koteswarao and M. Janardhan
Department of Chemistry, SVRM College, Nagaram, Guntur (District) Andhra Pradesh, India- 522268
*Corresponding Author E-mail: medikissi@gmail.com
ABSTRACT:
Two simple extractive spectrophotometric methods are described for the determination of Fluvoxamine as maleate (FXA) in pure form and in pharmaceutical formulations. These methods are based on the formation of ion association complexes of the FXA with 3-(4-(dimethyl amino) phenyl) acryl aldehyde (PDAC) (M1) and Ninhydrin (NH) (M2) in basic buffer of pH 9.8 followed by their extraction in chloroform. The absorbance of the chloroform layer for each method was measured at its appropriate max against the reagent blank. These methods have been statistically evaluated and found to be precise and accurate. The procedures described were applied successfully to the determination of the compound in their dosage forms. The results showed that the proposed procedures compared favorably with the reference method and satisfactory sensitivity, accuracy and precision. The optical characteristics such as Beer’s law limits, molar absorptivity and sandell’s sensitivity are reported. Regression analysis using the method of least squares was made to evaluate the slope (b), intercept (a) and correlation coefficient (r) and standard error of estimation (Se) for the drug.
KEYWORDS: Fluvoxamine maleate, spectrophotometric methods, statistical analysis, recovery studies.
INTRODUCTION:
Fluvoxamine1as maleate (Figure 1) is an antidepressant which functions as a selective serotonin reuptake inhibitor (SSRI) belonging to the chemical series, the 2-aminoethyl oxime ethers of aralkyl ketones in the treatment of a variety of depressed states2. Fluvoxamine is widely prescribed to treat major depressive disorder, and anxiety disorders such as obsessive compulsive disorder (OCD) generalized anxiety disorder (GAD), panic disorder, social phobia, and post-traumatic stress disorder (PTSD). Fluvoxamine is indicated for children and adolescents with OCD3. It is chemically designated as 5-methoxy-4'-(trifluoromethyl) valerophenone-(E)-O-(2aminoethyl) oxime maleate (1:1) and has the empirical formula C15H21O2N2F3.C4H4O4, molecular weight is 434.41. Fluvoxamine maleate is a white to slightly off-white, odourless, crystalline powder, sparingly soluble in water, freely soluble in ethanol and chloroform, practically insoluble in diethyl ether.
Figure 1
For the determination of fluvoxamine maleate in dosage forms, various analytical techniques including Polarographic4-5, HPLC6-9, TLC9, UV- Visible spectrophotometry 10-13 and Surfactant to dye binding degree method 14 are used. Fluvoxamine with its oxime ether group has a structural feature that could be used for electrochemical reduction. The analytically useful functional groups in FXA have not been fully exploited for designing suitable visible spectrophotometric methods and so still offer a scope to develop more visible spectrophotometric methods with better sensitivity, selectivity, precision and accuracy. Existing analytical methods reveal that relatively little attention was paid in developing visible spectrophotometric methods by exploiting the analytically useful functional groups. Hence there is a need to develop sensitive and flexible visible spectrophotometric methods which prompted the author to carry out in this accord.
Instruments: An Elico, UV – Visible digital spectrophotometer with 1cm matched quartz cells were used for the spectral and absorbance measurements. An Elico LI-120 digital pH meter was used for pH measurements.
Preparation of reagent solutions: Method M1: PDAC (BDH, 0.4%, 2.63x10-3 M): Prepared by dissolving 400 mg of PDAC in 100 ml of CH3OH; H2SO4solution made by Merck India Ltd.
Method M2: Ninhydrin solution (BDH 1%, 5.605x10-5m): Prepared by dissolving 1 gm of ninhydrin in 100 ml of acetone.
Ascorbic acid solution (BDH; 0.1%, 5.678 ´ 10-3M): Prepared by dissolving 100mg of ninhydrin in 100 ml of distilled water.
Buffer solution (pH 5.0): Prepared by diluting a mixture of 200ml of 0.5 M citric acid and 200 ml of 1.0 M NaOH solutions to 500 ml with distilled water and the pH was adjusted to 5.0.
Preparation of standard drug solution: 1 mg/ml solution was prepared by dissolving 100 mg of pure FXA in 100 ml of 0.1N HCl and this stock solution was diluted step wise with distilled water to get the working standard solutions of concentration of 500 mg/ml.
Recommended procedure:
M1: PDAC tried for developing the colour in alcoholic medium (methanol), PDAC was found to be superior for its sensitivity. This method involves the condensation of the FXA with PDAC in the presence of acid. The effect of various parameters, such as concentration and volume of PDAC, nature and strength of acid, order of addition of reagents, solvent for final dilution were studied and the optimum conditions developed and actual conditions chosen for the procedure were recorded.
M2: The method involves the reaction between drug and Ninhydrin reagent to produce blue colour. The conditions were fixed basing on the study of the effects of various parameters such as volume of Ninhydrin, nature and conc. of reducing agent, pH and volume of the buffer, heating time and temp, order of addition of the reagents, solvent for final dilution and stability of the colored products after final dilution. The optimum conditions were established by measuring the absorbances at 560 nm
Reference Method13: An accurately weighed amount of tablet powder equivalent to 100 mg of drug was transferred into a 100 ml volumetric flask. Added about 75 ml of ethyl alcohol and shaken well for about 15 min. The contents were diluted with ethanol upto the mark and mixed thoroughly. The solution was filtered. Then 2 ml of filtrate was pipette out into a 100 ml volumetric flask and made up the solution upto the mark with ethanol for obtaining a concentration of 20 mg/ml. Into a series of 5ml graduated tubes, aliquots of drug solution ranging from 0.5-3.0 mg/ml were taken and diluted to mark with ethanol. Read the absorbance at 240 nm against a solvent blank. The drug was read from its calibration graph
RESULTS AND DISCUSSION:
Optical Characteristics: In order to test whether the colored species formed in above methods adhere to Beer’s law, the absorbances at appropriate wavelength of a set of solutions containing varying amounts of FXA and specified of amounts of reagents were recorded against the corresponding reagent blanks. The Beer’s law plots of these recorded graphically. Beer’s law limits, molar absorptivity, Sandell’s sensitivity and optimum photometric range for FXA in each method were calculated. Least square regression analysis was carried out for getting the slope, intercept and the correlation coefficient values (Table 1).
Precision: The precision of the proposed methods was ascertained from the absorbance values obtained by actual determination of six replicates of a fixed amount of FXA in total solution. The percent relative standard deviation and percent range of error (at 0.05 and 0.01 confidence limits) were calculated for the proposed methods (Table 1).
Accuracy: To determine the accuracy of each proposed method, different amounts of bulk samples of FXA within the Beer’s law limits were taken and analysed by each proposed method. The results (percent error) are recorded in Table 1.
Interference studies: The effect of wide range of concomitants and other additives usually present in the formulations for the assay of FXA under optimum conditions were investigated. The commonly used concomitants and additives in the preparation of formulation such as talc (upto 250 fold excess (m/m) compared with FXA), boric acid (150-fold), stearic acid (70-fold), magnesium stearate (50-fold), Kaolin (40-fold), sodium lauryl sulphate (40-fold) and gelation (30-fold) when added in exess fold (as mentioned in paranthesis) did not interfere with the assay of FXA by proposed methods. However, for avoiding the interference of concomitants such as starch, lactose (if present), and the formulations were selectively extracted with appropriate organic solvent initially, since the interfering concomitants are insoluble in it.
Analysis of formulations: Commercial formulations (tablets) containing FXA were successfully analysed by the proposed methods. The values obtained by the proposed and reference methods for formulations were compared statistically with F and t tests and found not to differ significantly. The results are summarized in Tables 2. Percent recoveries were determined by adding standard drug to pre-analysed formulations. The results of the recovery experiments by the proposed methods are also listed in Table 2.
Chemistry of the colored species: The chemistry of the colored species formed in each one of the proposed methods for the assay of FXA has been presented in Scheme 1 and 2. The azomethine formation (colored species) in the reaction between PDAC and FXA may be represented as follows.
Scheme 1
In the present investigation, FXA which possesses NH2 in side chain when heated with Ninhydrin in presence of ascorbic acid afforded a blue violet colour product. The reaction pathway is shown in scheme 2
Table 1. Optical and regression characteristics, precision and accuracy of the proposed methods for FXA
Parameter |
M1 |
M2 |
|
lmax (nm) |
540 |
560 |
|
Beer’s law limits (mg/ml) |
10-100 |
20-100 |
|
Detection limit (mg/ml) |
3.790 |
4.278 |
|
Molar absorptivity (1.mol/cm) |
1.839 ´ 103 |
1.642 ´ 103 |
|
Sandell’s sensitivity (mg/cm2/0.001) absorbance unit) |
1.464 ´10-1 |
0.3661 |
|
Optimum photometric range (mg/ml) |
41.62-112.2 |
55.12-120 |
|
Regression equation (Y= a + bc) slope (b) |
8.889 ´ 10-3 |
3.768 ´ 10-3 |
|
Standard deviation on slope (Sb) |
1.056 ´ 10-3 |
1.198 ´ 10-3 |
|
Intercept (a) |
4.499 ´ 10-3 |
7.5 ´10-4 |
|
Standard deviation on intercept (Sa) |
7.010 ´ 10-2 |
7.948 ´ 10-2 |
|
Standard error on estimation (Se) |
6.685 ´ 10-2 |
7.579 ´10-2 |
|
Correlation coefficient (r) |
0.9994 |
0.9987 |
|
Relative standard deviation (%)* |
0.3564 |
0.3535 |
|
% Range of error (confidence limits) |
|
|
|
0.05 level |
1.563 |
0.4065 |
|
0.01 level |
1.450 |
0.6374 |
|
Formulations* |
Amount taken (mg) |
Amount found by Proposed Methods** |
Percentage recovery by proposed methods*** |
||||
M1 |
M2 |
Reference method |
M1 |
M2 |
|||
Tablet I |
100 |
100.03±0.43 F = 1.757 t = 1.162 |
99.86±0.28 F = 4.144 t = 1.263 |
99.91 ± 0.83 |
99.93±0.32 |
99.88±0.12 |
|
|
Tablet II |
100 |
100.02±0.58 F = 1.9503 t = 0.473 |
99.65±0.47 F = 2.970 t = 0.460 |
99.98 ± 0.62 |
99.96±0.17 |
99.92±0.14 |
|
|
Tablet III |
100 |
99.83±0.46 F = 1.996 t = 0.405 |
99.79±0.53 F = 1.504 t = 0.294 |
90.09 ± 0.44 |
99.94±0.15 |
99.94±0.10 |
|
|
Tablet IV |
100 |
99.53±0.42 F = 1.973 t = 1.4 |
99.77±0.37 F = 2.542 t = 0.61 |
99.95 ± 0.37 |
99.94±0.25 |
99.96±0.15 |
|
*Tablets from four different pharmaceutical companies
**Average ± standard deviation of six determinations, the t-and F-test values refer to comparison of the proposed method with the reference method. Theoretical values at 95 % confidence limit, F = 5.05, t = 2.57
***Recovery of 10 mg added to the preanalyzed pharmaceutical formulations (average of three determinations).
CONCLUSIONS:
The developed spectrophotometric methods for the estimation of FXA were found to be simple and useful with high accuracy, precision, and reproducible. Sample recoveries in all formulations using the above methods were in good agreement with their respective label claim or theoretical drug content, this suggesting the validity of the method and non interference of formulation excipients in the estimation.
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Received on 19.09.2010 Modified on 07.10.2010
Accepted on 24.10.2010 © RJPT All right reserved
Research J. Pharm. and Tech. 4(3): March 2011; Page 450-453