1. Field-flow fractionation (FFF)
Giddings JC (1966) A new separation concept based on a coupling of concentration and flow nonuniformities. Separation Science 1(1):123–125.
J. Calvin Giddings
University of Utah, Salt Lake City, USA
Nobel prize nominee: 1984 and 1992
First Commercialization: 1986 (FFFractionation)
Image courtesy Postnova Analytics
Slide modified from C. Cuss (ICHMET 2018)

2. Flow FFF can be used to separate major NP/colloids by size
Modified from Lead JR, Wilkinson KJ (2006) Aquatic colloids and nanoparticles: current knowledge and future trends. Environ. Chem. 3:159–171.
Mainly ionic, ‘truly dissolved’
Hydrated ions
Small inorganic complexes
(e.g. carbonates)
Dissolved organic matter
Exudates and metabolites
Degradation products
Humic substances M+ M+
M-CO3 M+
Mainly inorganic/mineral
Amorphous oxyhydroxides,
clays, other minerals
Adsorbed trace
elements
DOM adsorbed to surfaces M+ M+ M+ M+ M+
Slide modified from C. Cuss (ICHMET 2018)

3. Trace element fractograms
FFF-UV-ICPMS: Multiple post-separation analyses
UV-Visible absorbance (non-destructive)
Organic matter
Flow
Online or Offline ICP
ICP-MS (quadrupole)
Trace element fractograms
Offline EM
56Fe ❶ ❷ ❸ ❹
Flow
Transmission electron microscopy
Energy-dispersive x-ray spec.
0.6% Fe
0.01% Mn
Inorganic (metals)
Crossflow shut off
Slide modified from C. Cuss (ICHMET 2018)

4. Asymmetrical Flow FFF Where:
b0 is the channel breadth at the inlet triangle
bL is the channel breadth at the outlet triangle
z’ is the position of the focusing band
Leff is the effective channel length
Aeff is the effective channel cross section area
y is the tapered area

5. Asymetrical Flow FFF (AF4)
Liquid
Tunable eluent chemistry (pH, ionic strength)
Field generated by fluid cross-flow
AF4: asymmetrical channel geometry
Inlet (tip flow)
Inlet (focusing flow)
Slide modified from C. Cuss (ICHMET 2018)
Outlet (detector)

6. Asymetrical Flow FFF (AF4)
Liquid
Tunable eluent chemistry (pH, ionic strength)
Field generated by fluid cross-flow
AF4: asymmetrical channel geometry
Inlet (tip flow)
Inlet (focusing flow)
Slide modified from C. Cuss (ICHMET 2018)
Outlet (detector)

7. (-) Size separation only over about a 10-20 fold range in a given run
(Plus/minuses)
(-) Size separation only over about a fold range in a given run
(+) turning field off allows analysis of large particles (non-nano) that are outside separation range
(but these might be reversibly-sorbed NPs)
(-) Produces very dilute fractions
(+) ICP-MS sensitivity is high
(- ) Slow: run time up to one hour depending on size range
(- )Technique is challenging. Most common issue is poor recovery (nothing comes out)
(+) Is very reproducible
Element correlations versus size
Field Off
Javid et al, 2017

8. FFF-ICPMS for examining Contaminant Adsorption: pH-dependent Uranium adsorption to Hematite.

9. Centrifugal FFF

10. Particle diameter (m)
SdFFF Separations
of Illite Clay Mixture 1 1
( m)
200 nm 2
Relative Mass 2
( m)
0.1
0.2
0.3
0.4
0.5
0.6
Particle diameter (m)
500 nm

11. Electrophoretic mobility of Georgia Kaolinite Size Fractions

12. Single Particle ICP-MS
Single Particle Mode
(100 ms dwell)
Dwell time

13. Combining FFF and spICP-MS
Is it + Or

14. Core-shell particle analysis by FFF
30nm diameter Au core 15nm Ag shell
(60nm total diameter)
SedFFF-ICP-MS
(buoyant mass)
8.8 nm thick PVP-shell
spICP-MS data reported as equivalent spherical diameter

15. Fraction collection analysis by spICP-MS
SedFFF-ICP-MS
197Au spICP-MS
107Ag spICP-MS

16. Fraction collection analysis by spICP-MS
SedFFF-ICP-MS
197Au spICP-MS
107Ag spICP-MS
SdFFF elution time based on mass.
Density difference between Au and Ag does not explain size difference.
-27 nm Au should elute with 34 nm Ag.

17. Fraction collection analysis by spICP-MS
SedFFF-ICP-MS
197Au spICP-MS
107Ag spICP-MS
Au size is relatively constant
Ag size (coating thickness) increases
Results suggest (confirm) that Au and Ag are associated
Can be used to investigate elemental associations in complex minerals

18. Summary
Recent Improvements in Nanometrology (coming largely from ENP studies) facilitate:
Complex materials characterization
Environmental fate and effects studies
Earth science investigations of biogeochemical processes involving nanomaterials
Hyphenated techniques utilizing size separation/measurement (FFF) and quantification (single particle ICP-MS):
Provide more information on NP form and transformations
But remain challenging for wide-spread use
“Fingerprinting” of NP elemental/isotopic composition:
Can better define natural NP geochemistry
Assist in identification/quantification of engineered, incidental, and natural NPs
Requires further development in instrumentation and methods

19. Acknowledgements CSM Students (work presented): Angie Barber (Arcadis)
Katie Challis (CSM)
Dr. M. Montano (University of Vienna)
Logan Rand (CSM)
Collaborators (work presented)
University of Alberta: Chad Cuss
PostNova Analytics: SoheylTadjiki, Robert Reed
University of Utah: Shoeleh Assimi
Perkin Elmer: Chady Stephan,Hamid Badiei, Samad Bazargan, Dylan MacNair, Tyler Kidd (PerkinElmer)
Funding Sources:
NSF # ,
USEPA STAR Program # RD
ICEENN 2016 reunion