(666c) Triboelectric Behavior of Mannitol Powder with Respect to Important Influencing Factors

Stefan Karner, Nora Anne Urbanetz

Institute for Process and Particle Engineering, Graz University of Technology/Austria

Since most pharmaceutical powders and especially inhalation powders consist of small particles of insulating material electrostatic charge arises when contact of the particles among themselves or with other surfaces happens in powder handling processes. This triboelectric charge carried by the powder can cause problems like material loss, poor flowability and dosing behavior. The phenomenon of the emergence of charge and its impact on the characteristics of the powder are widely uninvestigated. Several scientists such as Murtomaa et al.², Zhu et al.⁵, Matsusaka et al.¹, Telko et al.⁴ and Rowley et al.³ examined the emergence of charge in common powder handling processes. The above mentioned problem of uniform dosing is particularly of high interest in dry powder inhalation manufacturing. Therefore the aim of this work is to investigate the triboelectric behavior of the new alternative dry powder inhaler (DPI) carrier material mannitol.

Spray dried mannitol was donated by Roquette Frères (Lestrem, France). It shows the characteristic diameters of d₁₀=80 µm, d₅₀=149 µm and d₉₀=209 µm. Charging experiments were carried out by blending the powder in a tumble blender (T2F Turbula®, Willy A. Bachofen AG - Maschinenfabrik, Switzerland) and measuring the charge in a Faraday cup connected to a high resistance electrometer (Keithley 6517 B, Keithley Instruments, USA). First the dependence of the arising charge on the mixing time was determined. Charge saturation was found after about 20 minutes mixing time. Sign and magnitude of this saturation charge can be influenced by varying the mixing process parameters. Therefore subsequent studies focused on the influences of the particle size, the mixing container size and the fines fraction present in the blend.

In contrast to other studies this work uses statistical tools like design of experiments to investigate the significance of the effects and the interactions of more than one influencing factors. The experimental data revealed strong influences of all investigated factors and also some interesting interactions between them.

In addition to the charging investigations also some discharging tests were performed. This was done by using design of experiments as well to check several influencing factors.

The obtained data are highly useful to improve the understanding of the emergence and impact of electrostatic charge on pharmaceutical powders, especially inhalation powders, and will help to enhance the performance of DPIs.

References

(1) Matsusaka, S.; Masuda, H. Electrostatics of particles. Advanced Powder Technology. 2003;14:143-166

(2) Murtomaa, M.; Savolainen, M.; Christiansen, L.; Rantanen, J.; Laine, E. & Yliruusi, J. Static electrification of powders during spray drying. Journal of Electrostatics. 2004;62:63-72

(3) Rowley, G. Quantifying electrostatic interactions in pharmaceutical solid systems. International Journal of Pharmaceutics. 2001; 227:47-55

(4) Telko, M. J.; Kujanpää, J.; Hickey, A. J. Investigation of triboelectric charging in dry powder inhalers using electrical low pressure impactor (ELPI(TM)). International Journal of Pharmaceutics. 2007;336:352-360

(5) Zhu, K.; Tan, R.B.H.; Chen, F.; Ong, K.H; Heng, P.W. Influence of particle wall adhesion on particle electrification in mixers. International Journal of Pharmaceutics. 2007;328:22-34