Table 2.

The preparation of calibration solutions of heavy metals.

Element	1	2	3	4	5	6
As	0	2	5	10	20	50
Hg	0	0.1	0.2	0.5	1.0	2.0
Pb	0	5	10	20	40	80
Cd	0	0.5	1	2	4	8
Cu	0	0.2	0.5	1.0	1.5	2.0