Mobile phase composition was tested with methanol/
phosphate buffer + tetrabutylammonium (30:70 and 70:30, v/v)
in C8 column (λ = 254 nm); and 0.2% metaphosphoric acid in
water solution, 0.2% metaphosphoric acid/methanol (95:5 and
90:10, v/v), 0.2% metaphosphoric acid/acetonitrile (95:5 and
90:10, v/v) and 0.2% metaphosphoric acid/methanol/acetonitrile
(90:5:5, v/v/v) inC18 column (λ = 254 nm). Those mobile phases
have not presented adequate response for ascorbic acid quantitation
since they were not able to identify the antioxidant
glutathione, as a component of the pharmaceutical/cosmetic
preparations, and provided unsuitable retention time for the
active substance (≈1 min) [28].