36. Solving a chemistry problem

185. In the fluorimetric determination of penicillin in the urine, it is pre-extracted with chloroform. A mixture of benzene, acetone, acetic acid and an acridine derivative is added to the extract. The latter forms a condensation product with penicillin, which is re-extracted with an acidified aqueous solution. The re-extract has an intense yellow fluorescence. When analyzing two urine samples (Va = 10 ml) with the addition of 1.0000 and 2.0000 μg of penicillin in this way, the measured values of the fluorescence intensity were 59.5 and 77.5 c.u., respectively. Calculate the concentration of penicillin (µg/ml) in the urine sample if the control sample gives a signal of 9.5 c.u.