The nanoparticle resolution of Electrical Low Pressure Impactor (ELPI) has been improved by designing and manufacturing a new impactor stage for the impactor. The measured cutpoint of the stage is 16.7 nm. The additional stage does not affect the properties (e.g. cutpoints) of other impactor stages. The performance of the new impactor construction was evaluated with laboratory and heavy duty diesel exhaust measurements. Based on the laboratory measurements the lower limit for the measured geometric mean diameter is expanded down to 11 nm. The diesel exhaust measurements made parallel with the new and the old construction show that the results are equal at large particle sizes. For nanoparticles, the resolution and precision are improved with the new construction. Using the new impactor stage and density analyzing method density can be analyzed even for 10 nm particles.