Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 7, pp. 1016−1021.
Pleiades Publishing, Ltd., 2013.
Original Russian Text © T.N. Poyarkova, E.V. Sotnikova, G.V. Kudrina, 2013, published in Zhurnal Prikladnoi Khimii, 2013, Vol. 86, No. 7, pp. 1084−1088.
ELECTROCHEMISTRY AND OTHER
PROCESSES OF CHEMICAL TECHNOLOGY
Application of the Coagulation Titration Method
for Quantitative Determination of the Content
of Anion-Active Emulsiﬁ ers in Latex
T. N. Poyarkova, E. V. Sotnikova, and G. V. Kudrina
Voronezh State University, Voronezh, Russia
Received February 12, 2013
Abstract—Possibility of fast quantitative determination of the content of emulsiﬁ ers of the alkyl sulfate type in
latexes by their titration in a strongly diluted (1 : 10
) state with a solution of a cation-active surfactant (cetylpyri-
dinium chloride) was demonstrated. The titration end point is determined as the abscissa of the point of a maximum
(cm) in the curve describing the dependence of the “minute turbidity” of the latex on the cetylpyridinium chloride
concentration. The inﬂ uence exerted by the length of the hydrocarbon radical in the cation-active surfactant on
the value of cm at the titration end point was studied.
Properties of synthetic latexes largely depend on
their content of surfactants. At present, there are no
sufﬁ ciently precise and fast methods for determining
such widely occurring in the industry of synthetic rubbers
(SRs) emulsiﬁ ers as alkyl sulfates and alkyl sulfonates.
Application of the extractive-photometric method
[1, 2], which is sensitive and sufﬁ ciently accurate for
determining the content of alkyl sulfates in latexes is
frequently impossible because of its being rather labor
consuming. Determinations of this kind can be based on
the reaction between cationic and anionic surfactants.
Reactions of this kind in aqueous solutions have
been rather well studied. For example, a comparative
assessment of three methods for determining the content
of sodium dodecyl sulfate (SDS) in aqueous solutions was
made in . Two of these methods are based on binding
of alkyl sulfate anions into an insoluble complex in the
interaction with a cationic surfactant (CS), followed by
turbidimetry of the resulting dispersion. One of variants
of the turbidimetric method consists in that SDS
solutions are titrated with cetyltrimethylammonium
bromide, and the other, in that an excess amount of
a cationic surfactant (myristyl trimethylammonium
bromide) is added at its concentration lower than the
critical micelle concentration and the turbidity of the
resulting dispersion is measured.
The turbidimetric method is attractive because of
being simple, fast and requiring no toxic solvents.
However, both of its variants described in  cannot
be used to determine anionic surfactants in latexes
because of the high turbidity of the dispersion even at
strong dilutions. In addition, introduction of cationic
surfactants into latexes causes their coagulation and
variation of their turbidity with time. The coagulation
is due to the interaction of long-chain cations (R
) of a
cationic surfactant introduced with anions (R
) of the
emulsiﬁ er in the adsorption layers of polymeric particles.
The formation of the insoluble R
complex leads to a
decrease in the surface electric charge of latex globules
and in the electrostatic repulsion potential barrier,
which provides the aggregative stability of the latex.
The variation of the turbidity with time characterizes
the coagulation rate , which depends on the degree
of binding of R– ions. Consequently, the concentration
dependence of the turbidity variation rate can be used
to ﬁ nd the end point in titration of latex with a cationic