Triboelectrification of Fractionated Crystalline and Spray‐dried Lactose

Previous work with dry powder inhaler systems has suggested that liberation of a fine drug on inhalation of a powder mix is less extensive when spray-dried lactose is substituted for crystalline lactose as the drug carrier. The aim of this work was to investigate the electrostatic charging tendencies of spray-dried and crystalline lactose which may give rise to these differences in drug separation. Triboelectrification of the lactose samples was effected through contact with the stainless steel surface of either a mixing vessel or a cyclone separator. Results from both techniques showed differences in charging propensity and particle-steel adhesion between spray-dried and crystalline lactose for certain size fractions including the 63–90 μm size used in dry powder inhaler systems. Although mechanisms involved in the attraction and separation of drug and carrier are not fully understood, the interparticulate forces will strongly depend on the properties of drug and carrier and therefore these differences in electrostatic charge may influence the processing of drug/carrier mixes and drug delivery from dry powder inhaler devices.