ISSN 1070-4272. Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 1, pp. 56 ! 59. + Pleiades Publishing, Inc., 2006.
Original Russian Text + L.S. Banyan, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 1, pp. 57! 61.
AND ION-EXCHANGE PROCESSES
Packing for High-Performance Liquid Chromatography
Based on Microspheric Particles of (Urea!Formaldehyde
Resin)!Silica Gel Composite
L. S. Banyan
Yerevan State University, Yerevan, Armenia
Received June 7, 2005
Abstract-Preparation of uniform microspheric particles of the (urea3formaldehyde resin)3silica gel com-
posite was studied. The suitability of this composite modified with C
groups as packing for reversed-phase
high-performance liquid chromatography was evaluated. The sorbent was modified using either octadecyldi-
methylchlorosilane or polymers containing C
groups, and the columns packed with the resulting sorbent
were studied. The experimental results showed that the polymeric modification allows efficient shielding of
the surface silanol groups.
Uniform microspheric particles find expanding ap-
plication in preparation of sorbents and supports for
chromatography, and thus the reproducibility of their
structural characteristics, primarily determined by re-
producibility of the particle size, is of particular im-
portance. Therefore, development of new procedures
for preparing microspheric supports for high-perfor-
mance liquid chromatography HPLC (both porous and
non-porous) is an urgent problem .
Iler et al. [4, 5] suggested a new procedure for
preparing uniform urea3formaldehyde resin micro-
spheres based on formation of coacervates as liquid
micrometer-size drops in the course of polymerization
of urea and formaldehyde in acidic silica sol. Oligo-
mers form coacervates bound by hydrogen bonds,
which contain silica or other hydrophilic colloidal
particles. Microspheric particles with the diameter
varying from 0.2 to 20 mm(5310 mm on the average)
are prepared using colloidal silica particles (53500 nm
size) whose parameters are easily controlled. The ad-
vantages of the above procedure for preparing (urea3
formaldehyde resin)3silica gel (UFR3SG) micro-
spheres [4, 5] are as follows: (1) it yields uniform
microspheric particles and thus eliminates fractiona-
tion problems and (2) it allows control of the particle
size in the course of polycondensation by changing
content of colloidal silica in the system.
Airapetyan et al. [6, 7] studied the effect of col-
loidal silica in the course of formation of uniform
The resulting UFR3SG particles can be used as
nonporous support for HPLC because they meet such
chromatographic requirements as rigid silica skeleton
and uniformity of the microspheric particle size (1.53
2.0 mm) typical for nonporous packing. The difference
in the particle size does not exceed 10% .
The suitability of the urea3formaldehyde resin
packing as HPLC sorbent was discussed in [12, 13].
Monolithic tube of urea3formaldehyde resin prepared
in situ is used as a new support for affinity chroma-
tography. This monolithic UFR tube consists of ag-
glomerates of 2-mm particles of irregular shape and is
characterized by biporosity. Cibacron Blue dye 
is used as affine ligand grafted to the support surface
A stationary phase for HPLC in which microspher-
ic particles (335 mm in diameters) are formed by con-
densation of hexamethylenetetramine with urea in the
presence of zirconyl chloride was reported in .
Preparation of microspheric UFR!SG particles.
Microspheric UFR3SG particles were prepared under
the conditions presented in Table 1. First, urea was
dissolved in concentrated hydrochloric acid. Then,
the mixture was diluted with distilled water, and the
required amounts of silica sol and formaldehyde
(Table 1) were added. The volume of silica sol (20%