Solubility behaviour of metals in ordinary vegetables after cell breakdown

Summary

The suitability of the mechanical cell breakdown by liquid shearing (ultra-turrax treatment) as an initial step of speciation of K, Ca, Mn, Fe, Cu, Zn, Rb and Sr in storebought vegetables is examined. The subject of the investigation are celeriac, chard, Jerusalem artichoke, kohlrabi, leek and spinach plants. Pre-cut parts of these plants are homogenised by ultra-turrax treatment in the presence of buffer. A contamination with respect to the elements of interest can be excluded. The homogenates are separated into cytosols (liquid fractions) and pellets (solid fractions) by centrifugation and the distribution of the elements is determined. Metals are analysed by total reflection X-ray fluorescence (TXRF) and the quantification is performed by using one internal standard. The results obtained are of great interest since the individual metals show a similar distribution in diverse plants. The metals K, Zn, Cu, and Rb predominate in all examined cytosols. Calcium and especially Sr, are not well transferred into a soluble form by ultra-turrax treatment. Iron is mainly bound to the pellets, as is Mn, though to a smaller degree. The quick and simple method of cell breakdown in fresh vegetable foodstuffs using liquid shearing transfers K, Cu, Zn, and Rb in significant percentages into a soluble form without contaminations. Consequently, a great fraction of these elements are directly accessible to further analytical separation procedures.