Assay of bromhexine hydrochloride in pharmaceutical formulations by extraction spectrophotometry

Transcription

1 Indian Journal of Chemical Technology Vol. 12, March 2005, pp Assay of bromhexine hydrochloride in pharmaceutical formulations by extraction spectrophotometry S V Murali Mohan Rao a, I Nageswara Rao b *,T Rama Subba Reddy b & C S P Sastry a a Department of Organic Chemistry, Foods, Drugs and Water, School of Chemistry, Andhra University, Visakhapatnam , India b Department of Physical and Nuclear Chemistry & Chemical Oceanography, School of Chemistry, Andhra University, Visakhapatnam , India Received 5 January 2004; revised received 1 December 2004; accepted 4 January 2005 Three simple and sensitive spectrophotometric methods (A-C) for the assay of bromhexine hydrochloride in pure and dosage forms based on the formation of chloroform soluble ion-associates under specified experimental conditions are described. Three acidic dyes, namely, Tropaeolin oo (TP oo, method A), Naphthalene blue 12BR (NB 12BR, method B) and Azocarmine G (ACG, method C) are utilized. The extracts of the ion-associates exhibit absorption maxima at 420, 620 and 540 nm for methods A, B and C respectively. Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges (2.0-10) μg/ml for method A, (5.0-25) μg/ml for methods B and C respectively. Beer s law and the precision and accuracy of the methods are checked by the UV reference method. The results are reproducible with an accuracy of ± 1.0%. The methods are found to be suitable for the determination of bromhexine hydrochloride in the presence of the other ingredients that are usually present in dosage forms. Keywords: Spectrophotometry, tropaeolin oo, naphthalene blue 12BR, azocarmine G. IPC Code: G01J 3/00; A61K 9/00 Bromhexine hydrochloride (BH) is an expectorant and is chemically known as 2-amino-3, 5-dibromo-Ncyclohexyl-N-methylbenzylamine monohydrochloride. The drug is official in IP 1, BP 2. The techniques used to estimate BH include HPLC 3,4, capillary electrophoresis/mass spectrometry 5, capillary gas chromatography 6 and spectrophotometric (UV 7-12, Visible ). Even though extraction spectrophotometric procedures are popular for their sensitivity in the assay of drugs, there are only two reports using acidic dyes 13 for the determination of BH, in pure and pharmaceutical formulations. During the course of efforts to develop sensitive visible spectrophotometric methods, it was observed that the analytically useful tertiary amino group in BH has not been properly exploited. The present paper describes three simple and sensitive extraction spectrophotometric methods for the determination of BH, based on its tendency to form chloroform extractable ion-association complexes with acidic dyes belonging to different chemical classes, namely, Tropaeolin oo (azo, method A), Naphthalene blue 12 BR (azo, method B) and Azocarmine G (phenazine, method C) under specified * For correspondence ( svmurali@rediffmail.com) experimental conditions by exploiting the basic nature of the drug molecule. Experimental Procedure Instruments A Milton Roy Spectronic 1201 and Systronics 106 digital spectrophotometer with 1 cm matched quartz cells were used for the spectral and absorbance measurements. An Elico LI-120 digital ph meter was used for ph measurements. Reagents All reagents and chemicals used were of analytical grade and doubly distilled water was used throughout. Aqueous solutions of TP oo (Flukas, 0.05%,), NB 12BR (BDH, 0.2%) and ACG (BDH, 0.05%) were prepared by dissolving the required amount in doubly distilled water. The solutions were washed with chloroform to remove the chloroform-soluble impurities. HCl solution (0.1 M for method A) and glycine-hcl buffer solution (ph 1.5 for methods B and C) were prepared. Preparation of standard drug solution A 1 mg/ml solution was prepared by dissolving 50 mg of pure BH in 50 ml of distilled water and this stock solution was diluted stepwise with distilled

2 RAO et al.: ASSAY OF BROMHEXINE HYDROCHLORIDE IN FORMULATIONS BY SPECTROPHOTOMETRY 171 water to obtain the working standard solution of concentrations 40 μg/ml for method A, 100 μg/ml for methods B and C respectively. Recommended method Methods A, B & C Aliquots of standard BH solution [ ml 40 μg/ml (method A), and ml, 100 μg/ml (methods B and C)] were placed in a series of 125 ml separating funnels. Then 6.0 ml of 0.1 M HCl and 2.0 ml of TP oo solutions (for method A) or 5.0 ml of ph 1.5 buffer and 2.0 ml of NB 12BR solution (for method B) or 2.0 ml of ACG solution (for method C) were added. The total volume of aqueous phase in each separating funnel was adjusted to 15 ml with distilled water and 10 ml of CHCl 3 was added. The contents were shaken for 2 min. The two phases were allowed to separate and the absorbances of the separated organic layer were measured at 420 nm (method A) or 620 nm (method B) or 540 nm (method C) against a similar reagent blank. The amount of BH was deduced from the calibration curve. Procedure for tablets or syrup The tablet powder or syrup equivalent to 100 mg of BH was accurately weighed and triturated with (3 20 ml) aliquots chloroform and insoluble portion was filtered off. The combined chloroform filtrate was made up to 100 ml with the same solvent to obtain a solution of 1 mg/ml. For methods A, B and C, the filtrate was evaporated to dryness and the residue was used for the preparation of solutions as under working standard solutions preparation. Results and Discussion Conditions under which the reaction of BH with each dye fulfils the essential analytical requirements were investigated. All the experimental conditions studied were optimized at room temperature (25±3 o C) and were established by varying one parameter at a time 18 and observing its effect on the absorbance of the coloured species. In the preliminary experiments, in view of developing methods of analysis suitable for assaying small quantities of BH, several acidic dyes such as Alizarin red S, Tropaeolin oo, Naphthalene blue 12 BR, Azocarmine G and Bromo phenol blue were tested at various ph ranges as the colour producing agents by a dye salt partition technique. Different organic solvents such as benzene, chloroform, carbon tetrachloride, ethyl isobutyl ketone were tested for the extraction of the ion-association complex formed between the BH and each dye. The criterion for determining the best dye was the highest absorbance values of the complex in the organic phase at the wavelength of maximum absorbance. The above studies reveal that three dyes namely TP oo, NB 12BR and ACG gave better results than the other dyes. These dyes also gave low absorbance for the reagent blank. Chloroform was suggested as the solvent of choice for the extraction of the coloured complex with respect to maximum stability. Fig. 1 shows the absorption spectra of the ion-association complexes of BH with the three dyes, extracted into chloroform and of the reagent blank, obtained as described in the procedure. These ion-association complex spectra show the characteristic λ max (420 nm, method A; 620 nm, method B and 540 nm for method C) values of the respective dye itself. Optimum conditions for ion-association In order to establish the optimum acid strength (for method A) or ph range (for methods B and C), the BH was allowed to react with the respective dye in dilute HCl ranging from M (method A) or aqueous solution buffered between ph (methods B and C) and the complex formed was extracted into chloroform for absorbance measurement. The results show that a quantitative Fig. 1 Absorption spectra of the ion-association complexes of BH with TP oo (o-o), NB 12 BR ( - ), ACG ( - ) against reagent blank [Tp oo] = M; [NB 12BR] = 3.17 x 10-3 M; [ACG] = M.

3 172 INDIAN J. CHEM. TECHNOL., MARCH 2005 extraction was produced with an acid strength of M HCl (method A) or between ph (methods B and C). All subsequent studies were carried out at 0.1 M HCl (method A) or ph 1.5 (methods B and C). The ph was adjusted using a glycine-hcl buffer solution (this buffer was chosen on account of its elevated complexing ability, which could be of use in overcoming interferences). The volume of this buffer added (4-10 ml), did not show any effect in methods B and C respectively. 6.0 ml of 0.1 M HCl solution (method A) or 5.0 ml of solution with ph 1.5 (methods B and C) was found to be optimal. The minimum shaking time was determined by varying the shaking time from 1-10 min, although 1 min was found to be sufficient but, prolonged shaking had no adverse effect on the extraction. Shaking time of 2 min was selected for this study. A ratio of 2:3 (methods A, B and C) of organic to aqueous phases was required for efficient extraction of the coloured species and lower reagent blank reading. It was found that better reproducibility and a lower reagent blank were achieved if the dye was purified by extraction with chloroform initially. Analytical data The optical characteristics such as Beer s law limits, molar absorption coefficient, Sandell s sensitivity, regression equation and correlation coefficient obtained by linear least squares treatment 19 of the results for the systems involving bromhexine hydrochloride with the mentioned dyes are presented in Table 1. The precision of each method was tested by estimating six replicates of BH within Beer s law limits. The percent standard deviation and the percent range of error at 95% confidence limits are given in Table 1. In order to confirm the utility of the proposed methods, they were applied to the estimation of BH in various pharmaceutical formulations and results are presented in Table 2. The results obtained by the proposed and UV reference methods for the dosage forms were compared statistically by means of F- and t- tests and were found not to differ significantly. As an additional check of accuracy of the proposed methods, recovery experiments were performed by adding a fixed amount of the drug to the preanalysed formulations and the results are summarized in Table 2. Composition of the ion-association complex Bromhexine hydrochloride being basic in nature, forms an ion-association complex with the acidic dye Table 1 Optical and regression characteristics, precision and accuracy of the proposed methods for BH Parameters Method A Method B Method C λ max (nm) Beer s Law limits (μg/ml) Molar absorptivity (1 mol -1 cm -1 ) Sandell s sensitivity (μg/cm 2 / absorbance limit) % of range error (confidence limit) (i) 0.05 level (ii) 0.01 level Regression Equation (y=a+bc)* Slope (b) Intercept (a) Correlation coefficient Relative Standard Deviation (%)** % Error in bulk sample *** *y=a+bc, where c is the concentration in μg/ml and y is the absorbance unit. **Average of six determinations considered. ***Average of three determinations. which is extractable into chloroform. The stoichiometric ratio of the dye to drug was determined by the slope ratio method 20 and found to be 1:1 (for methods A and C) or 1:2 (for method B). The quantitative measurement of the effect of complexation on acid-base equilibrium is most likely to be interpretable in terms of electronic, steric and other effects of complexing. The possible structure of the ion-association complex in each instance was established based on the analogy reports for similar types of molecules with acidic dyes and was further confirmed by slope-ratio studies. The protonated nitrogen (positive charge) of the drug molecule in acid medium is expected to attract the oppositely charged part (negative charge) of the dye and behave as a single unit being held together by electrostatic attraction as given in Scheme 1. Interference studies Results of the analysis of pharmaceutical formulations reveal that the proposed methods are suitable for their analysis with virtually no

4 RAO et al.: ASSAY OF BROMHEXINE HYDROCHLORIDE IN FORMULATIONS BY SPECTROPHOTOMETRY 173 Table 2 Assay of BH in pharmaceutical formulations Pharmaceutical formulations* (Labeled amount) % Recovery** Proposed methods ±S.D Method A Method B Method C Reference method*** 99.59± ± ± ±0.33 Syrup I F=3.20 F=1.79 F=1.61 (2mg) t=0.82 t=1.27 t= ± ± ± ±0.79 Syrup II F=1.06 F=1.15 F=1.57 (4mg) t=0.22 t=0.89 t= ± ± ± ±0..65 Tablet III F=2.44 F=2.40 F=2.27 (8mg) t=1.02 t=1.98 t= ± ± ± ±1.04 Tablet IV F=1.64 F=2.61 F=2.61 (8mg) t=0.66 t=0.71 t=1.10 *Syrup or tablets from two different companies. **Average ± standard deviation of six determinations; the t- and F- values refer to comparison of the proposed method with the reference method. Theoretical values at 95% confidence limit, t = 2.57, F = *** Reference method (BH 9 ) Scheme 1- Structures of TPoo, NB 12BR, ACG and their respective complexes with bromhexine hydrochloride. interference of the usual additives. The other active ingredients one or more among (salbutamol sulphate, pseudo ephedrine hydrochloride, phenylpropanolamine hydrochloride, paracetamol, terbutaline sulphate, guaiphenesin, dextromethorphan, chlorpheniramine maleate, diphenhydramine, menthol, phenylephedrine hydrochloride) which are present in certain pharmaceutical formulations also do not interfere as the exploited aromatic primary amino group in BH is not present in them. In addition, distinguishable solubility characteristics of BH and accompanying ingredients in different organic solvents can be taken into consideration for minimizing the interference of other ingredients further. Conclusion A significant advantage of an extraction spectrophotometric determination is that it can be applied to the determination of individual compounds in a multicomponent mixture. This aspect of spectrophotometric analysis is of major interest in analytical pharmacy, since, it offers distinct possibilities in assay of a particular component in a complex dosage formulation. In the present study, bromohexine hydrochloride was determined

5 174 INDIAN J. CHEM. TECHNOL., MARCH 2005 successfully as a pure compound as well as a component in representative dosage formulations. The proposed methods are applicable for the assay of drug (BH) and have the advantage of wider range under Beer s law limits. The decreasing order of sensitivity and λ max among the proposed methods are A>C>B and B>C>A respectively. The proposed methods are simple, selective and can be used in the routine determination of BH in bulk samples and formulations with reasonable precision and accuracy. References 1 Indian Pharmacopoeia 1996 and Addendum 2000 (Government of India, Ministry of Health and Family welfare. Controller of publications. New Delhi), British Pharmacopoeia, Vol II (HMSO, London)1996, Rauha J, Salomies H & Aalto M, J Pharm Bioded Anal, 15 (1996) Vasudevan M, Ravisankar S, George M & Ravi J, Indian Drugs, 37 (2000) Tanaka Y, Kishimoto Y, Otsuka K & Terabe S, J Chromatogr A, 817 (1998) Shimano M, Inoue Y, Matsuzaki R, Inde S & Yagasaki K, Kanzei Chuo Bunsekishoho, 34 (1995) Bhatia N M, Jain D K & Trivedi P, Indian Drugs, 35 (1998) Tantishaiyakul V, Poeaknapo C, Sribun P & Sirisuppanon K, J. Pharm Biomed Anal, 17 (1998) Gangwal S & Trivedi P, Indian J Pharm Sci, 61 (1999) Panda S K & Sharma A K, Indian J Pharm Sci, 6 (1999) Ajay S & Pnusu T, Indian Drugs, 36 (1999) Gupta V & Kaskhedikar S G, The Eastern Pharmacist, 42 (1999) Popa C, Nedelcu A, Arama C & Neagu A, Farmacia, 43 (1995) Babu S K, Ganapathi P A V, Raju N V S N & Madhu G, The Eastern Pharmacist, XLII (1999) Emmanuel J & Vieira A J, The Eastern Pharmacist, 29 (1986) Gaitonde R V & Ganadhish J K, The Eastern Pharmacist, 29 (1986) Geeta N, Murthy H R K & Baggi T R, J Inst Chem, 68 (1996) Massart D L, Vandeginste B G M, Deming S N, Michotte T & Kaufman L, Chemometric: A Textbook (Elsevier, Amsterdam), 1988, Pattergill M D & Sands D E, J Chem Educ, 58 (1979) Irwing H, Rossotti F T C & Williams R J P, J Chem Soc, II (1958) 1906.