contents
Samples were digested in a microwave oven (Abu Samra et al., 1975). A 0.2 g freeze-dried sample was treated with 4 mL of 65% HNO3 in a Teflon vessel which was placed in a metal holder and screwed to a carrousel. Samples were digested in a microwave oven at 175°C for 13 hrs. Digested samples were transferred to a 10 mL volumetric flask. The digestive extract was kept in scintillation vessels at room temperature. K, Mg and Mn contents were determined by Atomic Absorption Spectral photometry/AAS (Unicam M series, Cambridge, England) (Sulaiman, 2005)