posted by Brian .
Serum taken from a patient being treated with lithium for manic-depressive illness was analyzed for lithium concentration. A reading of 291 units was obtained for the intensity of the 671 nm red emission line. Then 1.00 mL of a 11.7 mM Lithium standard was added to 9.00 mL of serum, and this spiked serum gave an intensity reading of 729 units. What is the original concentration of Li in the serum?