please re set up my previous preparation for adding impurity.
Basic concept is adding 1 ml into one liter of solution will raise up 100ppm of metal impurities.
We need these solutions.
1. Fe
2. Cu
3. Zn
4. Cr
[11:06]
I think our Lab should keep these samples or documents, if not, you can do it again and let me confirm your calculation is right.