, Volume 38, Issue 9–10, pp 545–554 | Cite as

Rapid size characterization of chromatographic silicas by flow field-flow fractionation

  • S. K. Ratanathanawongs
  • J. C. Giddings


The particle size distributions of various silica support materials for high performance liquid chromatography (HPLC) and size exclusion chromatography (SEC) were obtained using flow/hyperlayer field-flow fractionation (Fl/Hy FFF), a form of flow FFF. The experimental procedure for each material required only 3–6 minutes. The resulting fractograms (representing detector response as a function of time) were mathematically treated to yield particle size distribution curves. Unlike most techniques, Fl/Hy FFF yields particle sizes free of any assumption about particle density or porosity. Approximate mean particle diameters and polydispersities were estimated directly from the fractograms and compared to those more correctly calculated from the size distribution curves. The importance of specifying the type of mean particle diameter (such, as area, mass, and number averages) being reported is illustrated. The good agreement between the FFF number-weighted size distributions and those obtained by scanning electron microscopy demonstrates the usefulness of Fl/Hy FFF for the rapid and accurate characterization of chromatographic silicas.

Key Words

Field-flow fractionation Flow field-flow fractionation Particle separation Particle size, measurement and distribution Chromatographic silica 

List of Symbols


corrected detector response at ti

% CV

percent coefficient of variation

% CVa

percent coefficient of variation from area distribution curve (Method II)

% CVp

% CV due to sample polydispersity contribution only

% CVpa

% CV polydispersity obtained from area distribution curve (Method II)

% CVpm

% CV polydispersity obtained from mass distribution curve (Method II)

% CVpn

% CV polydispersity obtained from number distribution curve (Method II)

% CVs

% CV due to system nonidealities

% CVt

% CV calculated from fractogram (Method I)


% CV calculated from SEM


particle diameter

\(\bar d\)

first moment of size distribution curve

\(\bar d_a\)

area averaged particle diameter (Method II)


diameter eluting at ti


series of diameters at equal intervals

\(\bar d_t\)

average particle diameter calculated from fractogram (Method I)

\(\bar d_m\)

mass average particle diameter (Method II)

\(\bar d_n\)

number average particle diameter (Method II)


size distribution curve at di


diameter-based selectivity


discrete time


retention time


retention time of particle of unit diameter

\(\dot V\)

channel flowrate

\(\dot V_c\)

cross flowrate

Greek σt

standard deviation of fractogram peak


standard deviation of size distribution curve


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Copyright information

© Friedr. Vieweg & Sohn Verlagsgesellschaft mbH 1994

Authors and Affiliations

  • S. K. Ratanathanawongs
    • 1
  • J. C. Giddings
    • 1
  1. 1.Field-Flow Fractionation Research Center, Department of ChemistryUniversity of UtahSalt Lake CityUSA

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