Abstract
In the current study, -cyclodextrin (-CD) inclusion concurrent with cationic surfactant shielding was firstly evaluated for the successful stabilization of L-ascorbic acid (AA) under ambient lab conditions followed by ultra-high performance liquid chromatography (UHPLC) and online preconcentration capillary electrophoresis (CE). The combination of 0.44mM -CD with 10mM cetyltrimethyl ammonium bromide (CTAB) cationic surfactant (-CD-CTAB) was significantly reduced the degradation of AA at pH 7.0 with 11 d stability. However, the combination of -CD with sodium dodecyl sulfate (SDS) anionic surfactant (-CD-SDS) gave only 1 d stability of AA. Moreover, -CD-CTAB complex was stabilized AA with 175- and 12-fold enhancement compared with individual -CD and CTAB, respectively. The formation of AA--CD-CTAB ternary complex was proved by following the chromatographic and electrophoretic behavior of AA in the absence and presence of -CD and CTAB species. Thus, the obtained results were very promising and clearly provided a higher stability for AA without any molecular changes which normally limited the application of different analytical methods. After that, the reversed phase UHPLC/UV and CE/UV methods were developed for the quantitative determination of AA in different commercially available samples including pharmaceuticals, drinking juices and milk samples. Good linearity within the concentration range 1-1000 mu g/mL was achieved with coefficient of determinations (r(2)) higher than 0.9995. The limits of detection were 0.39 and 0.56 mu g/mL by UHPLC and CE, respectively. The proposed methods could be suitable for the quality control of AA, providing simple, rapid and reliable approaches for routine analysis of different pharmaceuticals and food.
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