Influence of Electrical Charge of PTFE Filter on Weighing of Filter with Electric Microbalance

Abstract

The polytetrafluoroethylene (PTFE) filter has been recommended for the measurement of mass concentration of ambient fine particles smaller than 2.5 μm (PM2.5) . Since the PTFE filter tends to be negatively charged, the electrical charge would introduce serious error in the evaluation of PM2.5 concentration with electric microbalances. The present work investigated the influence of filter charge on the determination of filter mass as well as a method which minimizes the error due to the electrical charge, using the PTFE filter of 140 mg weight with a support ring.
It was found that that attractive electrostatic force exerting between filter and microbalance greatly influences the measured mass of filter and that the use of neutralizer can reduce the error, effectively. The use of filter measurement kit, which shields the electrical field from the filter, was also effective for reducing the error in the mass measurement of filter.