. Samples were prepared for analysis by
ICP-OES, F-AAS and TXRF by acid digestion. 20 mL of 1:3 HCl:HNO3
(Fisher TraceMetal Grade acids; Fisher Chemical, MA, USA) was
added to 1 g of sample in a 70 mL graduated polyethylene vial,
covered with a polyethylene watch glass and allowed to stand
overnight.