Development and validation of an analytical method for the assessment of methylparaben and propylparaben by HPLC-UV

Introduction
Parabens are the most common preservative agents used in food packaging, cosmetics and medicines. Although they are endocrine disruptors, these compounds are found in many commercialized medicines and pharmaceutical preparations, leading to safety concern when these medications are administered.
The objective of this work was to develop and validate an analytical method to perform content assay of methylparaben (MP) and propylparaben (PB) in pharmaceutical preparations to ensure they do not exceed the maximum limit allowed for these compounds

Materials and methods
An analytical method, using HPLC-UV analysis, has been developed to determine MP and PP strength in preparation. Parameters of the method are described as follows: the mobile phase was composed of a mixture of acetonitrile and ultrapure water (50/50; v/v) and the flow rate was settled at 1 mL/min. The column was a Purospher^® STAR RP-18 endcapped (5µm) 150x4.6 mm and the wavelength of the detector was settled at 254 nm. Calibration range of the method varies from 1 – 0.03µg/mL. Three levels quality controls were realized (0.03; 0.125 and 0.5µg/mL respectively low, medium and high level). Validation of the method was carried out in accordance with ICH Q2 R(1) international guideline using the following criteria : linearity, accuracy (precision and trueness) and specificity.

Results and discussion
The retention time of MP and PP were found to be respectively at 3.25 and 5.52min.
Calibration curves provided adequate linearity over the calibration range with correlations coefficients greater than 0.9995 and residual value lower than 14.78% The mean equation of the linear regression line was y= 311.47(±8.22)x + 0.474 (± 0.485) for the MP and y= 3254.714(±4.95)x + 0.546 (± 0.223) for the PP. Coefficients of variation obtained during repeatability and intermediate precision studies were lower than 5.33 and 6.43% respectively, whatever the quality control assessed. The mean percent recoveries obtained during the trueness study remained close to 100% of the expected value.
The choice of these parabens is due to the frequency of their use in the preparations.

Conclusion
The analytical method showed adequate linearity and accuracy, allowing the determination of MP and PP. The method was successfully applied to the estimation of MP and PP due to its simplicity, rapidness (analysis time less than 7min), and high precision. Although the dosing of excipients is not recommended, this dosing method allows the release of preparations containing parabens while ensuring that their concentration is below the accepted threshold values. This will allow to improve the quality of our preparations compounded in pharmacy.

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