Particle Bipolar Charge Measurement

Why is Bipolar Charge important?

The charge carried by inhalation aerosols has been found to affect both inhaler device performance and lung deposition. The charge levels have been found to be affected by materials used in the device, drug and carrier material used in the formulation, interaction between surfaces and the device, but can also be affected by environmental conditions such as temperature and humidity. Thus far particle charge studies have focused on particle net charge measurements since a method for measuring bipolar charge has not been available. These studies have, however, indicated that net charge measurements give insufficient information as the particles generated by one inhaler device can simultaneously carry both positive and negative charge (Kannosto et al. 2013). The Dekati® BOLAR™ is the solution for this and is the first commercially available instrument that can simultaneously measure both negative and positive charges.

The BOLAR™ has been used to measured bipolar charge size distributions of various different inhalation aerosols. For example measured DPI results clearly indicate the insufficiency of net charge measurements as the detected positive and negative charge levels can be very high compared to detected net charge results. This completely new information can significantly improve our understanding of particles’ behavior and knowledge on developing new inhaler devices.


Example of bipolar particle charge size distribution of a DPI.



The Dekati® Bipolar Charge Analyzer (BOLAR™) has been specifically designed for measuring bipolar charge of inhalation aerosols including DPIs (Dry Powder Inhalers), MDIs (Metered dose inhalers) and Nebulizers. The BOLAR™ features include:

  • The instrument inlet is designed for a standard USP port connection where the inhaler device can be connected to.
  • The measurement cycle is programmed for short time scale measurement each of which consist of data quality verification procedures.
  • Repeatability of the measured inhaler can be easily viewed after the measurement on the BOLAR™ display which can simultaneously show results from several previous measurements.
  • Different data saving options are available ensure protection of the data.
  • Instrument calibration and measurement cycle details can be programmed to be only accessed with a password and thus avoid user errors.
  • Data processing tools have been designed to easily analyze repeatability and reproducibility of measurements of individual shots or actuations
  • Sample flow rate optimized for inhaler development and calibrated for 30, 60 and 90 lpm.
  • Particles collected inside the bipolar detectors can be analyzed to determine the charge to mass ratio in different particle size fractions and for different polarity particles.














Hinds, Aerosol Technology 1998, second edition.

Karner, S, Urbanetz, N A: The impact of electrostatic charge in pharmaceutical powders with specific focus on inhalation-powders. Journal of Aerosol Science 2011, 42, 428-445.

Kannosto, J, Isherwood, H, Niemelä, V, Ukkonen, A: High Bipolar Electrical Charge Levels of Lactose Particles measured from DPI, RDD 2013

Glover, W, Chan, H K: Electrostatic charge characterization of pharmaceutical aerosols using electrical low-pressure impaction (ELPI). Journal of Aerosol Science 2004, 35, 755–764.

Kwok, P C.L. Noakes, T, Chan, H K: Effect of moisture on the electrostatic charge properties of metered dose inhaler aerosols. Journal of Aerosol Science 2008, 39, 211–226.

Telko, Martin J., Kujanpää J., Hickey A. J., Investigation of triboelectric charging in dry powder inhalers using electrical low pressure impactor (ELPI™), International journal of pharmaceutics, 336, 352-360, 2007.

Leung, S.S., Chiow, A.C., Ukkonen, A. & Chan H.K. Applicability of Bipolar Charge Analyzer (BOLAR) in Characterizing the Bipolar Electrostatic Charge Profile of Commercial Metered Dose Inhalers (MDIs). Pharmaceutical Research 09/2015. DOI 10. 1007/s11095-015-1786-z

Wong, J., Lin, Y.W., Kwok, P., Niemelä, V., Crapper, J. & Chan, H.K. Measuring Bipolar Charge and Mass Distributions of Powder Aerosols by a Novel Tool (BOLAR). 2015. Molecular Pharmaceutics 2015, 12(9). pp. 3433-3440. DOI:10.1021/acs.molpharmaceut.5b00443.

Wong., J., Kwok, P. C. L., Niemelä, V., Heng, D., Crapper, J., Chan, H.-K., Bipolar electrostatic charge and mass distributions of powder aerosols – Effects of inhaler design and inhaler material, J Aerosol Sci., 95, 104-117, 2016