it avoids the loss of large particl

it avoids the loss of large particles as well as the greater error introduced by the addition of debris such as salt or organic agglomerates (which can be up to 10 nm) or large agglomerateswhich have accumulated organic materials. Observed particleswere nearly always spherical (see Fig. 3), so the diameter was calculated based on the assumption that the threshold-area represented the largest circular cross-section
of a particle.