Methods are described for the multielement determination in three algae (bi
omonitors) samples by inductively coupled plasma optical emission spectrome
try (ICP-OES). A certified lichen material from the International Atomic En
ergy agency (IAEA) was used to verify the accuracy of the methods. A marked
depression in all signal measurements was observed due to acid interferenc
e of the digested samples. The matrix-matched acid procedure or internal me
thod of standard additions was applied to overcome the interferences. Best
results were obtained by applying the matrix-matched acid procedure.