Multiple charge correction in particle mass analyzers: Experimental validation of the interpolated average charge (INTAC) algorithm

Multiple charge correction is essential in charger-classifier systems, where aerosols acquire a distribution of charges. A key example is the unipolar charger–particle mass analyzer (PMA) system. Recently, the Interpolated Average Charge (INTAC) algorithm was introduced as a simplified method for multiple charge correction in such systems. This work experimentally validates the INTAC algorithm across various aerosol types. First, we compare experimentally measured average particle mass with INTAC predictions for spherical particles of known density, finding that the algorithm performs within an average absolute error of 8.09% ± 5.45% for particles smaller than 100 fg. Further validation is conducted on aerosols with diverse morphological properties, revealing that large errors can arise due to uncertainties in both the mass-mobility relationship and the charge acquired by aggregate particles. However, direct fitting to experimental charge and effective density data reduces the absolute average error to 5.64% ± 5.72%. Finally, we discuss the use of a unipolar charger–PMA system for selecting particles with a narrow mass distribution. Results indicate that such systems transmit a broad range of masses at smaller particle sizes, which should be considered when designing experiments.