Gamma tocopherol

The quinoa oil of the species Chenopodium quinoa Willd was donated by the company Plantus® S.A. RN/Brazil. Alpha-tocopherol, gamma-tocopherol, porcine gelatin (Type A) and Tween 20 were obtained from Sigma Aldrich®, while the whey protein isolate was obtained from Alibra®. As measured by the Biuret method, the protein content of porcine gelatin was 80% (w/w). And for whey protein isolate was 88% (w/w) according to the manufacturer.

Methanol (CAS# 67-56-1; LC-MS/MS grade) purchased from Fischer Scientific was mixed with deionized water from an ultrapure water purifications system (Aqua Solutions model RODI-C-11BL, Jasper, GA, United States) and formic acid (CAS# 64-18-6; chemical purity: ≥ 98%; ACS reagent) to form a 90% methanol: 10% water and 0.1% formic acid mobile phase.
VEA, DL-alpha Tocopherol acetate (CAS# 7695-91-2, ≥99% purity), (+)-alpha Tocopherol (CAS# 59-02-9, ≥99% purity), (+)-gamma Tocopherol (CAS# 54-28-4, ≥96% purity), delta-Tocopherol (CAS# 119-13-1, ≥99% purity), alpha-Tocopherol-(phenyl-¹³C₆) (≥99% atom purity, ≥96% compound purity), labeled vitamin E acetate - (trimethyl-d₉) (≥ 98 atom %; chemical purity: ≥98%) were all purchased from Sigma Aldrich (St. Louis, Missouri, United States).
Stock solutions and calibrators of unlabeled VEA and other tocopherols were prepared by individually weighing neat compounds using a calibrated analytical balance and dissolving each in methanol. Multianalyte working solutions were prepared from individual stocks and stored at −20°C until use. The internal standard stock solutions were prepared in a similar manner using labeled alpha-tocopherol-(phenyl-¹³C₆) and labeled VEA-(trimethyl-d₉) in methanol. A working solution containing both labeled tocopherols was prepared in methanol and stored at −20°C.