A solution of 1 ppm quinine in water has a relative fluorescence intensity of 88 (a.u.). The fluorescence intensity of a solution of 1 ppm quinine but with 300 ppb Cl- was 49. 5 mL of a solution with an unknown concentration of NaCl were diluted to a final volume of 250 mL. 10 mL of this second solution were diluted to 100 mL, and quinine was added to a final concentration of 1 ppm. The fluorescence intensity of the final solution of quinine and NaCl was 40. Determine the concentration of NaCl in the original solution, expressing the result in g/L.

Sol: 0.222 g/L