Procedures

Sample mass (mg)

Pretreatments^a

1

5

10

15

20

25

Only dispersant

2

5

10

15

20

25

1) 2 N HCl; 2) dispersant

3

5

10

15

20

25

1) 30% H₂O₂; 2)dispersant

4

5

10

15

20

25

1) 2 N HCl; 2) 30% H₂O₂; 3) dispersant

5

5

10

15

20

25

1) 30% H₂O₂; 2) 2 N HCl; 3) dispersant

6

10

15

20

25

200^b

1) 2 N HCl; 2) 48% HF

7

10

15

20

25

200

1) 2 N HCl; 2) 30% H₂O₂; 3) 48% HF