1070-4272/01/7412-2095 $25.00 C 2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 12, 2001, pp. 2095!2097. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 12, 2001,
Original Russian Text Copyright + 2001 by Vladimirova, Morgunova.
AND INDUSTRIAL ORGANIC CHEMISTRY
Spectrophotometric Study of Interaction in the System Sodium
Dodecyl Sulfate!Cetylpyridinium Chloride!Methylene Blue
T. V. Vladimirova and E. E. Morgunova
Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russia
Received May 7, 2001
Abstract-Complexation of a cationic dye (Methylene Blue) with anionic and cationic surfactants (sodium
dodecyl sulfate and cetylpyridinium chloride) was studied spectrophotometrically. The formation constants
of complexes formed in the system were estimated. Dispersion of the investigated system was studied as
a function of time and cetylpyridinium chloride concentration.
The presence of surfactants in wastewater over-
burdens the treatment by commonly accepted meth-
ods. By virtue of the fact that surfactants are phys-
ically and chemically reactive compounds, it is sig-
nificant to know which components of waste they can
interact with and what degree of their decomposition
is reached as a result.
Multicomponent systems containing two or more
different surfactants are of considerable theoretical
interest and practical significance. For example, sys-
tems containing a surfactant and a dye are widely used
in textile manufacture, making it topical to study in-
teraction between compounds of various classes in
Previously, we studied the interaction in systems
cationic dye3anionic surfactant and cationic dye3
anionic surfactant3nonionic surfactant .
It is known  that cationic surfactants may exist
in the presence of anionic surfactants in three forms:
(1) monomers (unassociated molecules), (2) mixed
micelles (after reaching CMC), and (3) precipitated
solid (at concentration above the product solubility).
It has been demonstrated previously  that Meth-
ylene Blue (MB) and sodium dodecyl sulfate (SDS)
form an ionic associate in solution.
The concentrations of MB (cationic dye), DDS
(anionic surfactant), and cetylpyridinium chloride
(CPC) (cationic surfactant) in the system investigated
, and 10
M, respectively. The quality
of SDS and CPC was determined as in . The optical
density of the solutions was measured on an SF-46
spectrophotometer over the range 2003700 nm at
l = 1 cm. The residual concentration of SDS and CPC
was determined photometrically after extraction with
To estimate the scattering factor F
, we measured
the absorption spectra over the range 5003700 nm and
then determined the slope of the linear portion of
the ln A3ln l plot. The size of colloid aggregates
was determined turbidimetrically . The solution
turbidity was estimated as t = 2.3A/l, where A is
the optical density measured at l = 400 nm and l is
the layer thickness.
We measured absorption spectra of MB over a
wide concentration range in the presence of SDS and
CPC. In the visible range, we found formation of no
associates other than the ionic associate SDS3MB. In
the UV range, we observed changes in the shapes and
positions of absorption bands in the systems MB3CPC
and MB3SDS3CPC as compared with the spectra of
the individual compounds (Fig. 1). These evolutions
reflect the interaction occurring in the investigated sys-
tems, suggesting the formation of new compounds .
From the optical density data obtained in solutions
with various concentrations of the components, the
logarithms of the association constants (log K) for
MB3SDS, MB3CPC, and MB3CPC3SDS were esti-
mated by the procedure described in  to be 2.50 +
0.09, 4.66 + 0.33, and 8.42 + 0.55, respectively.
Presumably, formation of MB3CPC3SDS is caused
by both coulombic and hydrophobic interactions .