title: Liquid chromatographic determination of geometrical retinol isomers and carotene in enteral feeding formulas.
abstract: The objective of the present study was to evaluate a practical method for separation and determination of geometrical retinol isomers and carotene in enteral feeding formulas and to analyze 17 samples of commercial formulas. By using a normal-phase HPLC column and a mobile phase consisting of 1-octanol in n-hexane, seven isomers of retinol were separated and identified from the standard solution after photolysis. For evaluation of Vitamin A activity in these formulas, simultaneous determination of total carotene was performed. The data about linearity, recovery, accuracy and precision showed the reliability of analytical procedures. In the unsaponifiable portion of samples of commercial formulas, six retinol isomers were identified: (E)-retinol; (Z)-13; (Z)-9; (Z,Z)-9,13; (Z,Z)-11,13 and (Z)-7-retinol. (Z)-13/(E)-retinol ratios ranged between 3 and 37%. The range of total Z/(E)-retinol isomers fell between 5 and 42%. Despite the high concentration of Z-isomers observed in various commercial enteral feeding formulas, none of the samples presented Vitamin A activity below 90% of that specified on the label.
authors.affiliation: Seção de Bromatologia e Química, Laboratório de Ribeirão Preto, Instituto Adolfo Lutz, Rua Minas 877, Ribeirão Preto 14085-410, SP, Brazil. rmdfavaro@ial.sp.gov.br
authors.forename: Rosa Maria Duarte
authors.initials: RM
authors.lastname: Fávaro
authors.forename: Maria Helena
authors.initials: MH
authors.lastname: Iha
authors.forename: Maria de Lourdes Pires
authors.initials: Mde L
authors.lastname: Bianchi
mesh_terms: D002338:Carotenoids / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004750:Enteral Nutrition; D007536:Isomerism; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014801:Vitamin A / Q000032:analysis*
chemical_list: D014801:Vitamin A; D002338:Carotenoids