Selenium Standard Solution preparation

Selenium Standard Solution preparation:

Selenium Standard Solution (100 ppm Se):
Dissolve 0.100 g of selenium in 2  mL of nitric acid. Evaporate to dryness. Take up the residue in 2 mL of water and  evaporate to dryness; carry out three times. Dissolve the residue in 50 mL of dilute  hydrochloric acid and dilute to 1000.0 mL with the same acid. 
Selenium Standard Solution preparation

Selenium Standard Solution (1 ppm Se):
Immediately before use, dilute with  water to 40 times its volume a solution containing selenious acid equivalent to  6.54 mg of H2SeO3 in 100.0 mL.