Method for simultaneous analysis of eight vitamin E isomers in various foods by high performance liquid chromatography and fluorescence detection.
The objective of this study was to optimize a method to investigate the occurrence and to quantify the full isomeric composition of vitamin E (α-, β-, γ- and δ-tocopherols and tocotrienols) in 6 vegetables (raw and cooked), 3 herbs/spices, raw and cooked eggs, vegetable oils (canola, olive and soybean), flaxseed and sorghum (flour and seeds) and soy (flour) by HPLC with fluorescence detection. Different conditions of extraction and analysis were tested. The optimized method consisted of direct extraction with solvent (hexane:ethyl acetate, 85:15, v/v). For analysis normal phase column was used with mobile phase consisting of hexane:isopropanol:acetic acid (98.9:0.6:0.5) with isocratic elution and fluorescence detection. Excellent separation of all isomers was obtained along with adequate quantification in the foods analyzed. Recovery rates of standards ranged from 91.3 to 99.4%. The linearity range for each isomer varied from 2.5 to 137.5 ng/mL (R² greater than 0.995 in all cases). Detection limits ranged from 21.0 to 48.0 ng/mL for tocopherols and from 56.0 to 67.0 ng/mL for tocotrienols, while quantification limits ranged from 105.0 to 240.0 ng/mL for tocopherols and from 280.0 to 335.0 ng/mL for tocotrienols. The optimized method was considered simple, fast and reliable, and also preserved vitamin E isomers when compared to validated methods involving saponification.
Laboratory of Vitamins Analysis, Department of Nutrition and Health, Federal University of Viçosa, Avenida Purdue, s/n, Campus Universitário, Viçosa, MG CEP 36561-000, Brazil.
Helena Maria
HM
Pinheiro-Sant'ana
Michele
M
Guinazi
Daniela da Silva
Dda S
Oliveira
Ceres Mattos
CM
Della Lucia
Bárbara de Lazzari
Bde L
Reis
Sebastião César Cardoso
SC
Brandão
D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004531:Eggs / Q000032:analysis; D005504:Food Analysis / Q000379:methods*; D007536:Isomerism; D016014:Linear Models; D010938:Plant Oils / Q000737:chemistry; D015203:Reproducibility of Results; D012639:Seeds / Q000737:chemistry; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence; D014675:Vegetables / Q000737:chemistry; D014810:Vitamin E / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification
D010938:Plant Oils; D014810:Vitamin E