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|Type:||Artigo de periódico|
|Title:||Comparison Of Normal-phase And Reversed-phase Gravity-flow Column Methods For Provitamin A Determination|
|Abstract:||Considering the high cost of HPLC, the use of preparative C18 packing material as stationary phase in classical gravity-flow columns is proposed as an alternative for developing countries. In the present study, three methods were compared, one utilizing a normal-phase MgO: HyfloSupercel column, developed with increasing concentration of acetone in petroleum ether and two utilizing C18 reversed-phase columns developed with acetonitrile-methanol-chloroform (RP-C18 method) or with decreasing concentration of water in acetone (modified RP-C18 method). Percent recoveries of β-carotene from the columns were 98, 96 and 98% and of the entire analysis (β-carotene added to kale) 92, 89 and 92%, for the normal phase, RP-C18 and modified RP-C18 methods respectively. No significant difference was observed in the provitamin A contents (exclusively β-carotene) of two leafy vegetables determined by the modified reversed-phase and normal-phase methods; however, significantly lower values were obtained by the RP-C18 method. The situation became more complicated when samples containing other provitamins were analyzed. For squash both types of stationary phase could separate α- and β-carotene; however, for tomato and red-fleshed papaya, part of lycopene remained mixed with β-carotene in both reversed-phase columns. Although β-cryptoxanthin was separated in the modified RP column, it was also mixed with lycopene in the RP column. For all samples, the normal-phase column demonstrated much better separation. © 1989 Friedr. Vieweg & Sohn Verlagsgesellschaft mbH.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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