Question

An HPLC method was developed 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 (first, second, third, etc.) is most of the ibuprofen lost?

Short answer

The largest percentage loss occurs between $1.0$and $1.5$hrs.

Step-by-step solution

Given information

The distribution of the analyte between a mobile phase and a stationary phase is the basis for HPLC separation.

Given the concentration of ibuprofen in rat plasma samples as part of a study of the time course of the drug in laboratory animals and the oral administration of a $10$mg/kg dose of ibuprofen to a laboratory rat, blood samples were taken at various periods.

Plot

Plot concentration of ibuprofen versus relative peak area

Slope of the graph $=$$\frac{y_2-y_1}{x_2-x_1}$

$=6.27$

Intercept of the graph $=$$3.27$

Equation y $=$$6.27x+3.27$

Explanation

The following is the ibuprofen concentration in blood plasma for each of the times:

Spreadsheet:

The greatest percentage loss happens between $1.0$and $1.5$hours, according to the spreadsheet.