Microsoft word - no. 115, vol.2, no.3, 649-654, rjc-425.doc

Ankush Gupta, Monica Gulati and Narendra Kumar Pandey*
*Department of Pharmaceutical sciences, Lovely Professional University, ABSTRACT
A simple, sensitive, spectrophotometric method in UV region has been developed for the simultaneous estimation of
benzoyl peroxide and tretinoin in bulk and semi solid dosage form (cream). Standard solution of benzoyl peroxide
shows maximum absorbance at 234.8 nm and tretinoin shows maximum absorbance at 348.6 nm. Beer’s Lamberts
law is obeyed in concentration range 1-9 µg/ml for tretinoin with regression, slope and intercept of 0.991, 0.0918
and 0 respectively while for benzoyl peroxide, Beer’s Lambert law is obeyed in concentration range 0.5-5 µg/ml
with regression, slope and intercept having 0.9984, 0.2069 and 0.0253 respectively. Method was validated for
linearity, range, accuracy, precision, recovery studies and interference study of mixture. All these parameters
showed the adaptability of the method for the quality control analysis of the drug in bulk and in combination
Keywords: Tretinoin, benzoyl peroxide, semisolid dosage form cream, absorbance interference study.

Tretinoin (3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexenyl)-nona-2,4,6,8-tetraenoic acid) is a vitamin A derivative used topically for the treatment of acne vulgaris1. It is yellow coloured amorphous powder, relatively insoluble in water and freely soluble in methanol2 as benzoyl peroxide is a potent antibacterial agent which is the first line drug in treatment of acne vulgaris3. The chemical structure2 of tretinoin and benzoyl peroxide is shown in fig1 and fig2. Fig.-2: Chemical structure of benzoyl peroxide (BPO)
The combination of both drugs would be beneficial for the treatment of mild to moderate stage of acne vulgaris4. However for the combination therapy of two drugs if they are administered in the form of a TRETINOIN AND BENZOYL PEROXIDE Ankush Gupta et al. single formulation, a simultaneous estimation of the two would be required. Literature survey revealed that there was no validated UV method for the estimation of tretinoin and benzoyl peroxide simultaneously by UV spectrophotometric method in bulk and semisolid dosage form. The present study is aimed to develop selective, precise accurate and reliable UV method for determination of BPO and tretinoin in mixture of bulk and semi solid dosage form. EXPERIMENTAL
Instrument and reagents:
A Systronic UV-Visible Spectrophotometer 2201, with 1 cm matched quartz cell was used for the
absorbance measurement. All the chemicals used were of analytical grade. Pure tretinoin and benzoyl
peroxide obtained from Shalaks Pharmaceutical, New Delhi and H.K group, Mumbai respectively.
Preparation of standard stock solution
Standard stock solution was prepared by dissolving tretinoin in methanol to make final concentration of
10µg/ml. Different aliquots were taken from stock solution and diluted with methanol to prepare series of
concentration from 1-9 µg/ml. The λmax was found to be 348.6 nm in methanol (fig6). Absorbance was
measured at 348.6 nm against methanol as a blank. The calibration curve was prepared by plotting absorbance versus concentration of tretinoin (fig3). The same procedure was used for benzoyl peroxide vice versa but dilution from stock solution was prepared from 0.5-5 µg/ml using ethanol as solvent. The λmax was found to be 234.8 nm (fig7). Absorbance was measured at 234.8 nm using ethanol as blank and calibration curve was prepared (fig4).
Multicomponent scan analysis for interference study in mixture of bulk
Prepared a stock solution of benzoyl peroxide (10µg/ml) in ethanol and also prepared the stock solution
of tretinoin (10µg/ml) in methanol. Took 5ml of each of stock solution and mixed it thoroughly, then
scanned the resultant mixture of tretinoin and benzoyl peroxide from 200-400 nm using UV
spectrophotometer (fig5).
Application of the proposed procedure for the determination of API’s in cream
The proposed procedure was adopted for the determination of tretinoin and benzoyl peroxide in cream.
200 mg of cream (2.5% benzoyl peroxide and 0.025% tretinoin) dissolved in 100 ml of 1:1 mixture of
ethanol and methanol. Then the solution was filtered through Whatmann filter paper. Then the
concentration of benzoyl peroxide and tretinoin was calculated in the resultant solution. The readings
were taken in triplicate.
Accuracy and Precision
Accuracy and precision were investigated by analyzing three concentration of tretinoin and benzoyl
peroxide mixture in three independent replicates on the same day (Intra-day accuracy and precision) and
on three consecutive days (Inter-day accuracy and precision). Intra-day and Inter-day relative standard
deviation was calculated5.
Recovery Studies
The standard addition technique was carried out by adding excipients, with the addition of 50%, 100%
and 140% of drugs respectively in sample solution. The percentage recoveries of three concentrations
were calculated.
Robustness was tested by making deliberate small changes in concentration of solvent used in estimation
of API’s and observed the changes in various parameters like absorbance maximum, Beer’s law limit,
slope, intercept and correlation coefficient5.
Statistical evaluation of analysis and recovery studies were carried out. The data obtained from the proposed method showed accuracy of method. The values of standard deviation were satisfactorily low. The percent recovery of 99% was indicative of accuracy of method.
Validation of Method
The method was validated with respect to linearity and range, accuracy and precision, interference study, recovery studies and robustness. Linearity and range
The prepared aliquots for tretinoin (1-9µg/ml) were scanned for absorbance at λmax 348.6 nm. The absorbance range was found to be 0.08- 0.813. These aliquots obeyed Beer-Lambert’s law with regression of 0.9991 and for benzoyl peroxide the aliquots prepared (0.5-5 µg/ml) were scanned for absorbance at λmax 234.8 nm. Absorbance range was found to be 0.085-1.017 with regression of 0.9984. The optical Accuracy and Precision
The data evaluated has been summarized in Table 2 and Table 3. Intra-day and Inter-day relative standard deviation values and the low RSD value obtained from the analysis of pharmaceutical formulations indicated good precision of the method. Absorbance interference study
The characterstic peak for tretinoin was obtained at 348.6 nm and for benzoyl peroxide it was obtained at 234.8. For check out the interference of absorbance of one component with other component the absorbance of tretinoin was seen at 234.8 nm it was -0.059 and for benzoyl peroxide at 348.6 nm it was -0.026. The result showed that there was no interference in the absorbance of each component in the mixture. Recovery Studies
The percentage recoveries of three concentrations were found to be close to 100%, indicative of high
accuracy. The high percent recoveries indicate no interference from ingredients and excipients that might
be present in formulation Table 4 and Table 5.
Repeatability is based on the results of the method operating over short time interval under same
conditions. The low RSD value of intra-day precision, recovery and pharmaceutical preparation showed
high repeatability.
The authors are thankful to M/s Shalaks Pharmaceutical, New Delhi and H.K group, Mumbai for providing gift sample of tretinoin and benzoyl peroxide respectively. Table-1: Optical characterstics for tretinoin and benzoyl peroxide (BPO) Correlation coefficient (r2) 0.9991 0.9984 Slope 0.0918 Std.plot of Tretinoin at 348.6 nm
Fig.-3: Standard Calibration Curve of Tretinoin at 348.6 nm S td plot of BPO in ethanol at 234.8 nm
Fig.-4: Standard Calibration Curve of BPO at 234.8 nm Fig-5: UV Absorption Spectra of Benzoyl Peroxide and Tretinoin mixture of Bulk Fig.-6: UV Absorption Spectra of Tretinoin Fig.-7: UV Absorption Spectra of Benzoyl Peroxide Table-2: Results of accuracy and precision for Tretinoin * Percentage RSD of three samples Table-3: Results of accuracy and precision for benzoyl peroxide * Percentage RSD of three samples Table-4: Results of recovery studies for tretinoin * Percentage RSD of three samples Table-5: Results of recovery studies for benzoyl peroxide * Percentage RSD of three samples REFERENCES
1. A. Krautheim and H.P. Gollnick, Clindermatol. 22, 398-407 (2004).
2. British Pharmacopoeia I, The Stationary office, London, pp, 41-16- 41-17 (2000).
3. Gollnick, H., Cunliffe, W., Berson, D., et al., J. Am. Acad. Dermatol. 49,1, S1-S37(2003).
4. Leyden, J.J. J.Am.Acad. Dermatol. 49(3), S200-S210 (2003).
5. S.R. Shahi, G.R. Agarwal, P.B. Rathi, N.V. Shinde, V.G. Somani, et al., Rasayan J. Chem., 1 (2), 390-

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