Simultaneous Determination of Saponins and Isoflavones in Soybean (Glycine max L.) by Reversed-Phase Liquid Chromatography with Evaporative Light-Scattering and Ultraviolet Detection
Abstract:The first validated analytical method permitting the simultaneous qualitative and quantitative determination of isoflavones and saponins in soy has been developed. It combines liquid chromatography with an ultraviolet and evaporative light-scattering detector (ELSD). Within less than 30 min, 6 isoflavones (detected at 254 nm) and 4 triterpene saponins (monitored with the ELSD) were baseline separated, using a reversed-phase C18 column and a mobile phase consisting of water and acetonitrile, both containing 0.025% triflouroacetic acid. The method was validated for limit of detection (LOD), linearity, repeatability, precision, and accuracy. LOD was 3.2–6.0 ng/mL for isoflavones and 10.4–14.2 μg/mL for saponins, and linearity was indicated by R2-values of 0.997 and higher. Intra- and interday precisions of the assay were below 7.0% for all of the compounds except for one, which was only present in trace amounts in the samples. Repeatability was indicated by very stable retention times and relative standard deviations well below 4.0% for multiple injections (n = 3). Accuracy was confirmed by recovery rates between 96.8 and 101.0%, respectively. Different sample matrixes were successfully analyzed, proving the wide range of applicability of this method, including soybeans, capsules, liquids, and instant soy drinks.
Document Type: Research Article
Affiliations: 1: University of Innsbruck, Department of Pharmacognosy, Institute of Pharmacy, 6020 Innsbruck, Austria. 2: University of Mississippi, National Center for Natural Products Research, Research Institute of Pharmaceutical Sciences and Department of Pharmacognosy, School of Pharmacy, University, MS 38677.
Publication date: September 1, 2004
- The Journal of AOAC INTERNATIONAL publishes refereed papers and reviews in the fields of chemical, biological and toxicological analytical chemistry for the purpose of showcasing the most precise, accurate and sensitive methods for analysis of foods, food additives, supplements and contaminants, cosmetics, drugs, toxins, hazardous substances, pesticides, feeds, fertilizers and the environment available at that point in time. The scope of the Journal includes unpublished original research describing new analytical methods, techniques and applications; improved approaches to sampling, both in the field and the laboratory; better methods of preparing samples for analysis; collaborative studies substantiating the performance of a given method; statistical techniques for evaluating data. The Journal will also publish other articles of general interest to its audience, e.g., technical communications; cautionary notes; comments on techniques, apparatus, and reagents.
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