AND CORROSION PROTECTION OF METALS
Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 11, pp. 1883−1889.
Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.A. Kiprianov, N.M. Pankratova, I.A. Ponomarev, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 11, pp. 1797−1803.
Potentiometric pH Sensors for Measurements
in Fluoride-Containing Solutions
A. A. Kiprianov, N. M. Pankratova, and I. A. Ponomarev
St. Petersburg State University, St. Petersburg, Russia
Received December 23, 2010
Abstract—The results of tests in ﬂ uoride-containing solutions were presented for an antimony electrode, solid-
state polyvinyl chloride-graphite electrodes modiﬁ ed by a quinone-hydroquinone series system, and electrodes
made of silicate glasses, in particular, of commercial formulations. A technique and criteria were proposed for
comparison of the performance characteristics of different glass electrodes in ﬂ uoride-containing solutions, and
samples most resistant to hydroﬂ uoric acid were identiﬁ ed.
Some industrial applications, in particular wastewater
analysis, often require pH measurement sensors resistant
to ﬂ uoride-containing solutions. Conventional glass elec-
trodes commonly used for pH measurements in process
ﬂ uids are unsuitable for this purpose.
The available publications recommend that pH in
ﬂ uoride-containing solutions be measured with the use
of pH sensors that either have long been known or are
currently under development, e.g., metal oxide [1, 2] and
quinhydrone  electrodes, membrane electrodes based
on a liquid ion-exchanger or on a neutral carrier [4, 5],
phosphate glass electrodes , and electrodes made of
specially formulated silicate glasses [7, 8].
However, the instruments proposed are often unﬁ t for
speciﬁ c tasks. For example, such interesting develop-
ments as plasticized membrane electrodes and phosphate
glass electrodes are unsuitable for application under
real process conditions. They exhibit low selectivity,
poor potential stability, and incomplete realization of
hydrogen function. At the same time, glass electrodes
that are currently used most successfully under process
conditions are not resistant to hydroﬂ uoric acid attacks. In
this connection, much effort has been dedicated in recent
decades to development of special glass formulations with
enhanced resistance to HF, but no criteria were provided
for evaluating the performance characteristics of the ﬂ u-
oride-resistant glass sensors proposed. For silicate glass
membrane electrodes the stability in ﬂ uoride-containing
solutions is determined by the ﬂ uoride concentration
and pH of medium, as well as by the residence time of
electrode in a speciﬁ c solution.
The versatility of the problem to be solved poses
the main difﬁ culty in selection of appropriate indicat-
ing electrode, and the lack of a universal tool motivates
further research and development aimed to create new
structures and adapt the existing ones for special usage.
As to the type of the reference electrode and the design of
the electrochemical cell, there is also no obvious choice
either, because the commonly used silicate materials are
susceptible to etching in ﬂ uoride-containing solutions.
In view of the above-said, in particular in regard to
development of new formulations of electrode glasses,
we carried out here comparative tests of three pH sen-
sors most promising for ﬂ uoride applications: an anti-
mony electrode, a solid-state polyvinyl chloride-graphite
electrode modiﬁ ed by a quinone-hydroquinone series
system, and electrodes prepared from various silicate
The electrode properties were examined by the po-
tentiometric method at room temperature with the use
of an mV/pH meter (I-130, Status-2) in a charge-transfer