Intra-particle sorption rate and liquid chromatographic bandbroadening in porous polymer packings .2. Slow sorption rate on a microparticle packing

The rate of sorption of naphthalene from solution in methanol-water (85:15) onto 10-mu m diameter particles of the macroporous poly(styrene-divinylbenzene) sorbent Hamilton PRP-1 is measured by the shallow-bed technique. The sorbent bed is 3 mm in diameter by about 0.3 mm high and contains only 1 mg of PRP-1, This bed is located in the slider of a very low hold-up volume valve. Linear velocity of naphthalene solution through the bed is high enough to exceed 400 bed volumes per second and the valve is capable of accurately providing flow times as short as 0.04 s. The curve of moles sorbed versus time is fit by an empirical tri-exponential rate equation. The parameters of this rate equation are used in a recently developed mathematical model to predict the plate heights and peak shapes of naphthalene peaks that would be expected to elute from a 15-cm long HPLC column of PRP-1 at various linear velocities, if intra-particle processes were the only source of bandbroadening. The predicted peaks are close representations of the peaks that are experimentally observed to elute from such a PRP-1 column. This demonstrates that slow intra-particle processes are the major cause of bandbroadening of naphthalene on PRP-1.