Design of a device for simultaneous particle size and electrostatic charge measurement of inhalation drugs

Purpose. To develop a device for simultaneous measurement of particle aerodynamic diameter and electrostatic charge of inhalation aerosols. Method. An integrated system consisting of an add-on charge measurement device and a liquid impinger was developed to simultaneously determine particle aerodynamic diameter and electrostatic charge. The accuracy in charge measurement and fine particle fraction characterization of the new system was evaluated. The integrated system was then applied to analyze the electrostatic charges of a DPI formulation composed of salbutamol sulphate-Inhalac 230® dispersed using a Rotahaler®. Results. The charge measurement accuracy was comparable with the Faraday cage method, and incorporation of the charge measurement module had no effect on the performance of the liquid impinger. Salbutamol sulphate carried negative charges while the net charge of Inhalac 230® and un-dispersed salbutamol sulphate was found to be positive after being aerosolized from the inhaler. The instantaneous current signal was strong with small noise to signal ratio, and good reproducibility of charge to mass ratio was obtained for the DPI system investigated. Conclusions. A system for simultaneously measuring particle aerodynamic diameter and aerosol electrostatic charges has been developed, and the system provides a non-intrusive and reliable electrostatic charge characterization method for inhalation dosage forms. © 2008 Springer Science+Business Media, LLC.