Vl. Kononenko et al., FEASIBILITY STUDIES ON PHOTOPHORETIC EFFECTS IN FIELD-FLOW FRACTIONATION OF PARTICLES, Journal of liquid chromatography & related technologies, 20(16-17), 1997, pp. 2907-2929
Citations number
21
Categorie Soggetti
Chemistry Analytical","Biochemical Research Methods
Various mechanisms of particles photophoresis, both of direct and indi
rect type, are considered theoretically. The analytical expressions ar
e obtained for photophoretic and photothermophoretic mobilities of par
ticles, and their dependence on particle size, optical, and physicoche
mical properties is analyzed. The motion of latex spheres, glass beads
, and carbon black particles of 3-22 mu m diameter, in water, under th
e action of focused Ar+-ion laser beam, was studied experimentally at
lambda=514.5 nm and power 0.1-0.8 W, using two arrangements. In the fi
rst one, the particles' motion was observed through the microscope. Th
e positive photophoresis (away from the light source) was registered f
or all kinds of particles. Photophoretic velocities of particles were
evaluated in connection with their size, optical properties, and laser
power density. In another arrangement, the laser power was focused at
the entrance glass window of a round metallic capillary, along its ax
is, in the direction of suspension flow inside the capillary. The elut
ion curves for polydisperse carbon black particles were registered in
the gravity-sedimentation FFF mode with the laser power sn-itched on a
nd off. Typical curves possessed a strong initial maximum, attributed
to the fraction of smaller particles, and a substantially lower second
ary maximum related to large particles. The action of light changed th
e shape of the first maximum and shifted to a smaller time the second
one. Both experimental and theoretical results show the possibility to
generate, under FFF conditions, the photophoretic velocities of parti
cles in the range 1-100 mm/sec, depending on the light intensity, whic
h are sufficient to accomplish their separation relative to size, opti
cal, and surface charge properties.