A mass correction method for the aerosol particle mass analyzer to measure the particle mass of sub-50 nm nanoparticles

The particle mass measurement instrument of the aerosol particle mass analyzer (APM) tends to underestimate the particle mass of sub-50 nm nanoparticles, limiting the APM mass measurement to larger particles. In the present work, a mass correction method was developed based on a calibration reference to correct the APM mass underestimation according to a measured mass-based dimensionless parameter λ_c,P(m_APM). The correction was tested using laboratory generated silver nanoparticles and ambient nanoparticles. It was found that the measured effective density variations of silver nanoparticles due to different extent of APM mass underestimation at different operating conditions were reduced by the correction method with a significant improvement of R-squared from 0.40 to 0.87. In addition, about 20% increase in the effective density from 0.91 to 1.09 g/cm³ was observed for 30 nm ambient wet nanoparticles using the correction method. The difference between the raw and corrected effective densities is due to the mass underestimation by the APM itself, which should be corrected in the data analysis program of the APM.