Suppression of agglomeration in fluidized bed coating. III. Hofmeister series in suppression of particle agglomeration

Purpose. Fourteen kinds of salts consisting of various cations and anions i n the Hofmeister series were used as additives for suppression of particle agglomeration in the fluidized bed coating. We attempted to clarify the rel ationship between the suppression effect of the salts and the Hofmeister se ries of their consistent ions. Methods. Fluidized bed coating was carried out with hydroxypropylmethyl cel lulose (HPMC) aqueous coating solution containing the salts and Celphere(R) as core particles. To elucidate the salting-out power of the salts for HPM C, the transmittance of the coating solutions at 600 nm was measured at var ious temperatures and the phase separation temperature (T-PS) was determine d from the values at 50% transmittance. Results. A high suppression effect was observed when the salts including hi gh order ions in the Hofmeister series were added to the coating solution. T-PS decreased in the presence of the salts except for sodium iodide and so dium thiocyanate and lowered with the higher order ion in the Hofmeister se ries. The particle agglomeration was suppressed with decrease in T-PS Of th e HPMC aqueous coating solution. Conclusions. It has been suggested that the suppression effect of a salt on the particle agglomeration depended on the salting-out power of the salt. We regard sodium citrate and potassium citrate as very useful pharmaceutica l additives for the suppression of particle agglomeration in actual pharmac eutical coating.