determination in the digested solutions was performed by inductively-coupled plasma optical emission spectrometry (ICP-OES) using a Perkin Elmer Optima 3.300 DV™ spectrometer (Norwalk, CT). Solutions of each element were prepared from analytical reagent-grade chemicals (Merck), using high-purity water obtained from a Milli-Q water purification system (Millipore, Bedford, MA) (Naozuka et al., 2010).