Postharvest analysis of vitamin C and inorganic cations in lettuce by CZE

In the present work, we used capillary zone electrophoresis (CZE) for the analysis of Vitamin C and inorganic cations (potassium, sodium, calcium, and magnesium) in lettuce (Lactuca sativa) during postharvest storage. The leaves of the creasphead lettuce samples were treated with 18 M omega water for cation analysis and, alternatively, with 3% wt/vol oxalic acid solution for ascorbic acid extraction. They were then homogenized and centrifuged, and the supernatants were introduced into the capillary for CE analysis. The cation analysis was performed on an uncoated fused-silica capillary column of 75 microns i.d. and 50 cm total length, using 15 mM creatinine, 15 mM alpha-hydroxyisobutyric acid, acetic acid, pH 4.00, as running buffer at an applied voltage of 20 kV. Indirect on-line UV detection was carried out at 214 nm. The content of Vitamin C was measured using an uncoated fused-silica capillary column of 50 microns i.d. and 45 cm total length; 10 mM sodium tetraborate, 10 mM sodium biphosphate, pH 9.00, as background electrolyte at an applied voltage of 20 kV. On-line UV detection was achieved at 254 nm.