Element

Certified Concentration

Observed Concentration (n = 2)

Rel. Error (%)

Recovery (%)

Cu

25.1 ± 3.8

25.9 ± 2.4

3.2

+103.2

Cr

71.0 ± 11

69.8 ± 3.7

1.7

−98.3

Mn

513 ± 25

496.1 ± 18

3.3

−96.7

Zn

191 ± 17

202.2 ± 19

5.9

+105.9