Estudo da cinética de liberação da vitamina B3 intercalada em hidróxidos duplos lamelares e hidroxissais lamelares

Abstract

Considering that many vitamins can be easily degraded, the present work aims to use two inorganic matrices, layered double hydroxides (HDL) and layered hydroxide salts (HSL), as an option for a slower release and to provide better thermal stability for vitamin administration. LDHs have the general formula [M2+1+xM3+x(OH)2]x+[An- ]x/n.yH2O, where M2+ corresponds to a divalent metallic cation, M3+ corresponds to a trivalent metallic cation and An- corresponds to the intercalated anion. HSLs, on the other hand, have the general formula M2+(OH)2-x(An-)x/n.yH2O, where M2+ corresponds to a divalent metallic cation, Zn2+ and An- correspond to intercalated anions. Initially, the compound HDL/B3 intercalated with vitamin B3 was prepared by the coprecipitation method. Subsequently, the characterization of HDL/B3 and HSLs (previously synthesized) was done by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermal analysis (TGA). The release evaluation occurred by fitting the experimental data using Elovich, Freundlich, Bhaskar, First Order and Second Order models. XRD characterization confirmed the intercalation of vitamin B3 in layered matrices with the value of the basal distance calculated by Bragg's Law (HDL/B3 = 15.4 Å - bilayer; HSL/B3-1 = 15.43 Å - bilayer and 9.92 Å, - monolayer; HSL/B3-2 = 9.63 Å - monolayer). Using FTIR, characteristic bands of vitamin B3 were observed, corroborating what was identified by XRD results. With the TGA/DSC analysis, it was analyzed that pure vitamin B3 starts its thermal decomposition at 155 °C and, after intercalation, there was an improvement in thermal stability at 163 °C (HDL/B3) and 175 °C (HSL/B3-1 and HSL/B3-2). It was also possible with the thermogravimetric analysis to estimate the general formula of the compounds, being Zn0,75Al0,25(OH)2(Vitamina B3)0,54.1,06H2O (HDL/B3), Zn5(OH)8(Vitamina B3)9,7.5,06H2O (HSL/B3-1) and Zn5(OH)8(Vitamina B3)9,7.5,06H2O (HSL/B3-2). The sustained release of vitamin B3 for HDL/B3 was 20.57% up to 79.64 h, for HSL/B3-1 it was 68.8% and for HSL/B3-2, it was 56.9 % up to 44.1 h, respectively. The Elovich, Freundlich, Bhaskar and Second-Order models showed satisfactory correlation coefficients (R2 between 0.97-0.98) for HDL/B3, while for HSL/B3-1 it was fitted with two models (Bhaskar – R2 0.98; Second Order – R2 of 0.97), whereas the HSL/B3-2 was Bhaskar's model (R2 – 0.96). Therefore, the organic-inorganic hybrids obtained by niacin intercalation have nutraceutical properties, improving thermal stability and slow release, being suitable for applications in the food industry with added nutritional value.