Simultaneous Determination of Multiple Amino Acids in Different Organs of Selenium-Enriched Radishes by High-Performance Liquid Chromatography

Accurate profiling of amino acids and selenoamino acids is crucial for evaluating the nutritional quality of selenium-enriched crops. To provide a reliable and accessible tool for routine food monitoring, this study employed pre-column derivatization high performance liquid chromatography (HPLC) method for the simultaneous determination and compositional analysis of 17 standard amino acids, selenocystine (SeCys2), and selenomethionine (SeMet) in various organs of selenium-enriched radish. Chromatographic separation was performed using a C18 column and a mobile phase of sodium acetate buffer (pH 5.25) and acetonitrile under gradient elution, with diode array detection (DAD) at 360 nm. Method validation demonstrated excellent linearity (R2) ≥ 0.995 for all 19 amino acids within their tested ranges. The limits of detection (LODs) and limits of quantitation (LOQs) were 0.06 to 0.21 mg/L and 0.19 to 0.68 mg/L, respectively. The spike recoveries ranged from 88.2% to 101.7%, while the intra-day and inter-day relative standard deviations (RSDs) were ≤3.09% and ≤4.25%, respectively. The levels of total, essential, selenoamino and taste-active amino acids in the leaves exceeded those in the taproot, with the highest total content of 2398.41 mg/kg found in leaves at the primary growth stage of the taproot. The total content of selenoamino acids ranged from 2.65 to 6.78 mg/kg. This method enables the simultaneous quantification of various amino acids, including selenoamino acids, in different organs of selenium-enriched radish throughout its entire growth period, providing a theoretical basis for the development of selenium-fortified products.