Studies were carried out with an F-1000 symmetrical FFF system
(Postnova Analytics, Salt Lake City, UT) equipped with a 1 kDa
regenerated cellulose membrane directly connected to a PerkinElmer
Elan DRC II ICP-MS using a MiraMist pneumatic nebulizer.
An Agilent 1100 variable wavelength detector was placed in-line
between the FFF and ICP-MS systems to collect UV absorbance
data. The mobile phase consisted of water containing 0.01% FL-70
and 0.01% NaN3 and separation was achieved using a channel
flow rate of 1.00 mL/min with a cross flow rate of 0.75 mL/min.
Elution time was converted to particle size based on a separate
experiment using polystyrene bead size standards (20, 50, and
100 nm, Postnova Analytics). The ICP-MS was operated in standard
mode with a nebulizer flow rate of 0.8 mL/min and a plasma power
of 1250 W.