The 1st Annual Postnova Analytics Field Flow Fractionation (FFF) User Meeting was held on September 15, 2017, in Park City, Utah, at the beautiful Goldener Hirsch Inn. The meeting featured top-notch scientific presentations from renowned researchers in a variety of disciplines, stimulating discussion, and an outstanding dinner to finish the event.
Meeting room at the Goldener Hirsch Inn. From left: Bruce Gale, University of Utah; Thorsten Klein, Postnova Analytics; Jim Ranville, Colorado School of Mines; Soheyl Tadjiki, Postnova Analytics; Scott Olsen, Postnova Analytics; and Shoeleh Assemi, University of Utah.New developments at Postnova
Postnova founder and CEO Thorsten Klein opened the event with a talk on the history of FFF and Postnova’s newest technologies, “FFF: Past, Present, and Future.” Klein recounted the interesting details of Professor Cal Giddings’ invention of FFF at the University of Utah, and showed a wide variety of FFF separation instruments and in-line detectors used over the past 50 years. He also presented the newest addition to the Postnova characterization platform, electric and flow FFF, which combines flow field and electric field in a single channel to provide information on size distributions (flow) and surface charge properties such as electrophoretic mobility and zeta potential (electric).
Application of FFF to nanoparticle and colloid measurements in the environment
Professor Jim Ranville from the Colorado School of Mines presented on a variety of engineered nanomaterial analysis applications in his talk, “Analyzing Complex Nanoparticles by Combining Single Particle Inductively Coupled Plasma Mass Spectrometry (spICP-MS) and FFF” (see Figure 1). Determining the environmental concentration and physicochemical form of nanoparticles (NPs) released from nano-enabled products is an important component of the risk assessment of nanotechnology. One important form of NPs are heteroaggregates produced with background colloids present in the environment. Another is NP-polymer fragments, which are released during the use and disposal of polymer nanocomposites. NPs that contain metals can be quantified and sized using spICP-MS. When these NPs are associated with other materials (i.e., heteroaggregates and polymer coatings) the size determined by spICP-MS will not be the same as their hydrodynamic size. Analysis by spICP-MS of fractions collected from FFF separations provides a means to determine the NP form more fully. The presentation gave details of an examination of Ag-NPs heteroaggregated to silica colloids (model natural colloids) and Au particles coated with polymer, the latter being a model for polymer-NP fragments. Complementary results were obtained for centrifugal FFF and asymmetrical FFF coupled to spICP-MS.
Figure 1 – These data show analysis of a Au core/Ag shell nanoparticle. The top left panel shows coelution of Au and Ag in the particle from centrifugal FFF separation. The right two panels show single particle ICP-MS size analysis of the fraction collected from 28 to 30 minutes (red bar on left graphs). The bottom left panel shows the core and shell sizes measured from each fraction collected across the centrifugal FFF fractogram. (Slide reproduced with permission of Jim Ranville, Colorado School of Mines.)Postdoctoral researcher Chad Cuss discussed the development and application of flow FFF coupled to ICP-MS in an ultraclean metal-free facility at the University of Alberta in Edmonton, Alberta, Canada (see Figure 2). The lab is called the SWAMP facility, for the analysis of trace elements in soil, water, air, manure, and plants. The SWAMP facility uses a 300-Dalton polyethersulfone FFF membrane to separate dissolved (i.e., <0.45 𝜇m) trace elements into different colloidal species: mainly ionic and small species <300 Da in size, organic-associated elements, and iron-associated elements. Rigorous QA/QC practices such as routine membrane cleaning and calibration using polystyrene sulfonate particle size standards are used to ensure low detection limits (e.g., ca. 2 ppt Pb, 0.9 ppt U), and precise size measurements (e.g., 986 ± 6 Da for Suwannee River Natural Organic Matter standard, n = 5). Statistical fractogram deconvolution is also applied to separate overlapping peaks on fractograms, facilitating the complete and repeatable measurement of trace element distributions among different colloidal forms. This method is being applied to assess the transport and preferential uptake of micronutrients and potentially toxic trace elements in surface waters and soil pore waters based on size/colloidal species, and to trace the source of trace element inputs to rivers.
Figure 2 – These data show FFF-ICP-MS analysis of two river water samples to separate different colloidal species: mainly ionic and small species <300 Da in size, organic-associated elements, and iron-associated elements. This method is being applied to assess the transport and preferential uptake of micronutrients and potentially toxic trace elements in surface waters and soil pore waters based on size/colloidal species, and to trace the source of trace element inputs to rivers. (Slide reproduced with permission of Chad Cuss, University of Alberta.)Analysis of clay nanoparticles using centrifugal FFF contributes to mechanism of clay swelling
Dr. Shoeleh Assemi from the Department of Metallurgical Engineering, University of Utah, presented “Analysis of Swelling Clay Nanoparticles Using Centrifugal Field Flow Fractionation (CFFF).” It was demonstrated that Ca- and Na- montmorillonite could be distinguished by their CFFF elution profile. Using the projected area obtained from electron microscopy images and volume from CFFF data, thicknesses of the primary and swelled particles could be compared. A mechanism for clay swelling was proposed using CFFF, ICP-MS, and molecular dynamics simulations results. Data were also presented for characterization of kaolinite, halloysite, and sepiolite nanoclay particles.
FFF applications in pharmaceutical and health studies
Professor Mikhail Skliar from the University of Utah discussed the application of centrifugal FFF techniques in obtaining subpopulations of exosomes with homogeneous biophysical and molecular characteristics, with the ultimate goal of characterization of these materials for cancer research.
Bryan Bernat from Pfizer gave a talk entitled, “AF4 Analysis of Pharmaceutical Nanoparticles.” A variety of nanoparticles were evaluated by flow FFF with refractive index and multiangle light scattering detection. The results were generally consistent with orthogonal techniques as supported by a recent publication on the topic, "Comparison of Miniaturized and Conventional Asymmetrical Flow Field-Flow Fractionation (AF4) Channels for Nanoparticle Separations" (Separations 2017, 4, 8).
Applications of FFF outside commercially available instruments
Professor Bruce Gale of the University of Utah and Director of the Center of Excellence for Biomedical Microfluidics gave an excellent overview, “Applications of Electrical Field-Flow Fractionation.” He reviewed the development and applications or electrical FFF (ElFFF), specifically covering the current models for ElFFF, best applications of ElFFF, and methods to convert biological samples to carriers that work with ElFFF. Gale showed specific examples of ElFFF being used for analysis, including fractionation of exosomes, peptides, nanoparticles, and viruses.
Discussion and social program
An energetic discussion period followed the lectures and continued into the night over an outstanding dinner. New interlab collaborations were initiated between attendees, potential new users were allowed to see the high level of research attained by researchers using Postnova FFF, and the meeting atmosphere was inspiring to all.
Robert Reed, Ph.D., is sales and application specialist, Postnova Analytics Inc., 230 South 500 East, Ste. 110, Salt Lake City, UT 84102, U.S.A.; tel.: 801-521-2004; e-mail: [email protected]