Development of an on-line lab-on-valve micro-solid phase extraction system coupled to liquid chromatography for the determination of flavonoids in citrus juices.

An on-line lab-on-valve system for renewable micro-solid phase extraction coupled with high performance liquid chromatography with photodiode array detection was developed for the determination of hesperidin and diosmin in natural and commercial citrus samples. The method is based on the automatic loading of 8 mL of sample into the C18 resin, followed by matrix clean-up and elution of the analytes with 0.27 mL of acetonitrile. Next, 0.02 mL of the extract were injected into the chromatographic system. Separation was performed by using a Symmetry® C18 column (250 × 3.0 mm x 5.0 μm) with a mobile phase consisting in a mixture of methanol, acetonitrile and acidic water (pH = 2.5) in gradient mode at 0.58 mL min-1. The detection wavelength was chosen as 285 nm. Limits of detection, quantification and relative standard deviations were lower than 0.1 μg mL-1, 0.3 μg mL-1 and 4.1%, respectively.