An HPLC method was develop for the separation and determination of ibuprofen in rat plasma samples as part of a study of the time course of the drug in laboratory animals. Several standards were chromatographed and the following results obtained:

Next, a 10 mg/kg sample of ibuprofen was administered orally to a laboratory rat. Blood samples were drawn at various times after administration of the drug and subjected to HPLC analysis. The following results were obtained:

Find the concentration of ibuprofen in the blood plasma for each of the times given above and plot the concentration versus time. On a percentage basis, during what half-hour period (1 ^st , 2 ^nd , 3 ^rd   etc) is most of the ibuprofen lost?

Ibuprofen Concentration, mg/mLPeak Area 0.5 5.0 1.0 10.1 2.0 17.2 3.0 19.8 6.0 39.7 8.0 57.3 10.0 66.9 15.0 95.3 Time, hr.Peak Area 0.5 91.3 1.0 80.2 1.5 52.1 2.0 38.5 3.0 24.2 4.0 21.2 6.0 18.5 8.0 15.2