Purpose. To optimize the intercalation conditions of ferulic acid, an antioxidant compound, into a synthetic lamellar anionic clay such as Mg-Al-hydrotalcite for a safe skin photoprotection. To study ferulic acid stability, at different pH and temperatures, using a factorial design model. Methods. The intercalation products were prepared incubating hydrotalcite in aqueous solutions of ferulate sodium salt at 6 different temperatures (25-32-37-45-52-60°C) for 4 and 8 days. Quantitative determination of intercalated ferulate was performed by thermogravimetric analysis at heating rate of 5°C min–1 in airflow. The supernatant was analyzed by RP-HPLC to evaluate the presence of ferulic acid degradation products. Elution was performed in an isocratic manner with a mixture of water- CH3COOH and acetonitrile (66:34, v/v). Ferulic acid stability study was carried out at pH 2.2, 4, and 7.4 at 4, 37, and 60°C. Ferulic acid was analyzed by RP-HPLC. Results. In all the intercalation products, ferulate content was found to be about 48 % w/w except when the intercalation was carried out at 52°C for 8 days and at 60°C for both 4 and 8 days in which it was 40.39, 39.99 and 34.99% respectively. At 25, 32 and 37°C, the supernatant chromatograms showed only a single peak corresponding to ferulic acid. The other supernatant chromatograms showed additional peaks whose intensities increased with temperature and/or intercalation time. It was suggested that the ferulic acid degradation influences its intercalation into the matrix. The factorial design showed that higher is the pH and the temperature, higher is the ferulic acid degradation rate as reported in term of constant rate value k. Conclusion. It is possible to improve the intercalation efficiency carrying out the process at low temperatures, optimizing pH conditions during 4 days needed for completion of the reaction as assessed by the ferulic acid stability study.

Optimization of the intercalation conditions of ferulic acid into a synthetic lamellar anionic clay.

SCHOUBBEN, Aurelie Marie Madeleine;BLASI, PAOLO;GIOVAGNOLI, Stefano;RICCI, Maurizio;ROSSI, Carlo
2005

Abstract

Purpose. To optimize the intercalation conditions of ferulic acid, an antioxidant compound, into a synthetic lamellar anionic clay such as Mg-Al-hydrotalcite for a safe skin photoprotection. To study ferulic acid stability, at different pH and temperatures, using a factorial design model. Methods. The intercalation products were prepared incubating hydrotalcite in aqueous solutions of ferulate sodium salt at 6 different temperatures (25-32-37-45-52-60°C) for 4 and 8 days. Quantitative determination of intercalated ferulate was performed by thermogravimetric analysis at heating rate of 5°C min–1 in airflow. The supernatant was analyzed by RP-HPLC to evaluate the presence of ferulic acid degradation products. Elution was performed in an isocratic manner with a mixture of water- CH3COOH and acetonitrile (66:34, v/v). Ferulic acid stability study was carried out at pH 2.2, 4, and 7.4 at 4, 37, and 60°C. Ferulic acid was analyzed by RP-HPLC. Results. In all the intercalation products, ferulate content was found to be about 48 % w/w except when the intercalation was carried out at 52°C for 8 days and at 60°C for both 4 and 8 days in which it was 40.39, 39.99 and 34.99% respectively. At 25, 32 and 37°C, the supernatant chromatograms showed only a single peak corresponding to ferulic acid. The other supernatant chromatograms showed additional peaks whose intensities increased with temperature and/or intercalation time. It was suggested that the ferulic acid degradation influences its intercalation into the matrix. The factorial design showed that higher is the pH and the temperature, higher is the ferulic acid degradation rate as reported in term of constant rate value k. Conclusion. It is possible to improve the intercalation efficiency carrying out the process at low temperatures, optimizing pH conditions during 4 days needed for completion of the reaction as assessed by the ferulic acid stability study.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11391/42209
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