2. A reversed-phase HPLC column of dimensions 4.6 mm diameter by 150 mm length is used at a liquid flow rate of 1.0 mL/min. An unretained compound elutes after 0.82 min. A compound with a KOW of 25 takes 2.88 min. to elute when using a mobile phase of 90% water/10% acetonitrile. Assuming the KC is equal to the KOW, calculate the stationary phase volume. A. 0.049 mL B. 0.082 mL C. 0.50 mL D. 1.00 mL E. 1.12 mL

To solve this problem, we need to understand the basic principles of High Performance Liquid Chromatography (HPLC). In HPLC, the retention time of a compound is determined by its partition coefficient (Kc), which is the ratio of the concentration of the compound in the stationary phase to its concentration in the mobile phase.

The problem states that the partition coefficient (Kc) is equal to the octanol-water partition coefficient (Kow), which is given as 25.

The retention time (tr) of the compound is given as 2.88 min, and the retention time of an unretained compound (t0) is given as 0.82 min.

The volume of the mobile phase (Vm) can be calculated from the flow rate (F) and the retention time of the unretained compound (t0) using the formula:

Vm = F * t0

Substituting the given values:

Vm = 1.0 mL/min * 0.82 min = 0.82 mL

The volume of the stationary phase (Vs) can be calculated from the partition coefficient (Kc), the volume of the mobile phase (Vm), and the retention time of the compound (tr) and the unretained compound (t0) using the formula:

Vs = Vm * ( (tr/t0) - 1) / Kc

Substituting the given values:

Vs = 0.82 mL * ( (2.88 min / 0.82 min) - 1) / 25 = 0.049 mL

So, the volume of the stationary phase is approximately 0.049 mL, which corresponds to option A.