Where ηn is the transport efficiency, Qsam is the sample flow rate (mL min−1), tdwell is the dwell time (ms per event), fNP is the average number of standard nanoparticle pulses (no. of pulses per event) and
N
ciency ηn can be calculated based on Eq. (1) if the number concentration of standard AuNPs is known. C is the analytical metallic calibration curve and the mass flux calibration curve W can be calculated based on Eq. (2). Spulse corresponds to the nanoparticle intensity, Sbkgd is the background intensity, fm is the mass fraction of analytical element (fm = 1 when the analytical element is Ag or Au) and m is the slope of mass flux calibration curve W. ηi is the particle ionization efficiency, and the ηi for silver and gold nanoparticle is 100% (Laborda et al., 2011). The ionization efficiency will need to be determined if the parti- cles are not ionized fully into the plasma. One way to detect the ioniza- tion efficiency ηi is to compare the mass concentration of acid-digested samples with the undigested ones. The nanoparticle mass mNP is calcu- lated based on Eq. (3). Assuming that nanoparticles are monodisperse and spherical, the diameter of the nanoparticle dNP (nm) can be deter- mined using the nanoparticle mass (Eq. (4)) where ρ is the particle den- sity (g/cm3).
NP
is the number concentration of nanoparticles. The transport effi-