Elemental analysis of 346 varieties of quinoa: Development and validation of microwave plasma optical emission spectrometry (MP-OES) method

Elemental analysis of foods is important for quantifying dietary nutrients and toxic elements. Recently, microwave plasma optical emission spectrometry (MP-OES) has emerged as an economical alternative to inductively coupled plasma (ICP) for routine elemental analysis. Herein, an MP-OES method was developed, validated, and applied to the quantification of 19 elements across 346 cultivars of quinoa. The method demonstrated good sensitivity for metal, but not non-metal, elements. Validation, using a standard reference material (NIST 1567b rice flour), demonstrated trueness of 72-106 % and precision of < 8 % relative standard deviation. These results demonstrate that MP-OES can be used as an accurate and economical method for routine elemental analysis of foods like quinoa. Nutritionally relevant minerals, including B, Mg, Mn, P, Cu, Fe, K, and Zn were found in relatively high concentrations across all varieties, while toxic elements, including Cd, Cr, Ni, and Ag were below the detection limit, though there was wide variation in mineral content across the germplasm. By selecting mineral-rich cultivars for future cultivation and breeding efforts, increasing quinoa production and consumption may contribute to increased intakes of essential minerals that are deficient in populations worldwide.