II-7
Matec Applied Sciences
56 Hudson St., Northborough, MA 01532 Ph: (508) 393-0155 Fax: (508) 393-5476
www.matec.com
e-mail: [email protected]
12. Calibration:
The CHDF 2000 is factory pre-calibrated. Each fractionation cartridge is provided with a floppy disk. The
floppy disk contains calibration curve files. The eluant flow rate and type at which the cartridge must be
operated are indicated on the floppy disk label, a typical flow rate is 1.4 ml/min. Periodic field
recalibration can be performed by the user directly through the CHDF software.
13. Calibration Material:
The recommended calibration materials are monodisperse polystyrene latexes. These are available from a
wide variety of commercial sources or directly from Matec Applied Sciences.
14. Warranty:
Complete one year limited warranty, excluding replaceable CHDF cartridge.
ANY ATTEMPT TO REMOVE OR TAMPER WITH THE INTERNAL PLUMBING OF THE
FRACTIONATION CARTRIDGE WILL VOID THE WARRANTY. THE USE OF ELUANT OTHER
THAN THOSE SUPPLIED BY MATEC APPLIED SCIENCES ALSO VOIDS THE WARRANTY.
2.5 THEORY OF OPERATION
The behavior of macromolecules and particles in suspensions flowing through capillary tubes has been
studied in detail because of its importance in certain biological phenomena, such as the transport of red
blood cells through the smaller capillaries in the circulatory system (1), and for use in particle
fractionation methodology.
The separation of particles by size due to hydrodynamic effects occurring in the flow of suspensions
through capillaries was first examined by Di Marzio and Guttman in 1970 (2,3). A particle exhibiting
Brownian motion suspended in a viscous fluid undergoing Poiseuille flow within a capillary tube will
sample all accessible radial positions if the particle elution time is sufficiently long. The closest approach
of the particle center to the inner wall of the capillary will be limited to a distance equal to the particle
radius. As the particle size increases, it will become increasingly unable to sample the slowest moving
eluant streamlines near the capillary wall. As a consequence of this, the particle velocity will exceed the
average velocity of the eluant and the velocity of smaller particles. This effect is based only on the particle
size and is not a function of the particle density or composition. In addition to this exclusion effect, the
longitudinal and radial particle displacements are affected by the presence of the capillary wall, and by a
fluid inertial force.
The Capillary Hydrodynamic Fractionation CHDF 2000 instrument from Matec Applied Sciences uses
these phenomena to determine particle size and size distributions in the sub-micron range. The instrument
moves the eluant and the particles through a set of capillaries, measures the particle concentration leaving
the system as a function of the transit time, and relates this transit time to that of well characterized
monodisperse size standards used in the calibration procedure. Through a mathematical interpretation of
the raw data, the true particle size and size distribution is established.
The software uses two particle extinction cross section curves, one for particles that absorb UV light and
one for those that do not, in order to compute the sample particle numbers. These curves are plots of
particle extinction cross section against particle size. The particle size is determined from the particle
elution time. The number of particles is calculated from the following expression:
Ni = (D.O.)/Rext,i
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