Mineral element analysis was performed on freeze-dried
samples. After dry-ash mineralization at 450 C the minerals
were extracted in an acid mixture (2 mL HCl 0.5 mL/
mLþ2 mL HNO3 0.5 mL/mL) and made up to 50 mL of distilled
water. For Ca and Mg determination, a dilution with La2O3
(58.6 mg/L acidified deionized water) was performed in order to
avoid interferences.