A fast and selective method to determine phenolic compounds in quinoa (Chenopodium quinoa Will) seeds applying ultrasound-assisted extraction and high-performance liquid chromatography

A simple and fast ultrasound-assisted extraction (UAE) method was optimized employing a chemometric technique to determine caffeic acid, vanillic acid, quercetin 3-β-d-glucoside, p-coumaric acid, vanillin, trans-ferulic acid, benzoic acid, quercetin, kaempferol and myricetin in quinoa seeds. Applying a central composite design, UAE conditions were established at 39 °C for 10 min, which is up to 12-fold lower than reported extraction times. Chromatography was performed on Phenomenex Kinetex XB C18 (150 mm × 4.6 mm, S-5 µm) column using a binary mobile phase composed of ammonium formate (0.01 mol L−1, pH 3.0) and acetonitrile (0.1% formic acid) at a flow rate of 0.5 mL min−1. Validation was performed following International Conference on Harmonization recommendations. Calibration data fitted a linear regression model with R2 > 0.999. Repeatability (n = 6) and intermediate precision (n = 3) in matrix showed relative standard deviation (RSD) values lower than 2.89 and 3.61%, respectively. Selectivity was evaluated by mass spectrometry (MS), without observing interference compounds. The proposed method was applied to determine the phenolic compound content in ten quinoa seeds samples from different varieties, finding a concentration range from 1.1 to 2.0 mg kg−1. The proposed method proved to be a fast and selective alternative to evaluate phenolic compounds in quinoa seeds.