Russian Journal of Applied Chemistry, 2010, Vol. 83, No. 11, pp. 2055−2057.
Pleiades Publishing, Ltd., 2010.
Original Russian Text © V.Ya. Khentov, V.V. Semchenko, T.V. Lipkina, M.S. Lipkin, L.N. Velikanova, 2010, published in Zhurnal Prikladnoi Khimii, 2010,
Vol. 83, No. 11, pp. 1925−1927.
Restoration of Cu-Selective Electrodes
V. Ya. Khentov, V. V. Semchenko, T. V. Lipkina, M. S. Lipkin, and L. N. Velikanova
South-Russian State Engineering University, Novocherkassk, Russia
Received March 18, 2010
Abstract—Donor-acceptor interaction of a Cu-selective electrode screening layer with salicylalaniline in N,N-di-
methyl formamide resulting in a membrane sensitization with respect to copper(II) ions was studied.
Ion-selective electrodes (ISE) have found wide ap-
plication for determination of concentration and activ-
ity of cations and anions [1, 2]. Fields of usage of such
electrodes are extensive: from analytical chemistry up
to industrial analysis and monitoring of technological
processes. Existing techniques of making ISE mem-
branes are based on dispersing an active component
in a medium of an inert binding agent. A membrane
is made by molding or rolling of the obtained mass
with a subsequent thermal treatment. In these cases it
is not possible to reproduce ionic contacts of an active
material between separate grains. It results in reduc-
tion of the sensitivity of Cu-selective electrodes down
to 15–20 mV/pCu, which corresponds to a detection
limit of Cu
ions of 10
M. To eliminate this
disadvantage, a freshly prepared membrane is held in
a solution of ions under determination for several hours
. As a result the sensitivity can be increased up to
26–28 mV/pCu. However during storage and explora-
tion the membrane sensitivity decreases. A reason of it
is the hydrolysis of the active component of the CuS
membrane and the appearance of a screening layer on
the membrane surface. Therefore a permanent monitor-
ing of the electrode state and its frequent replacements
are necessary in the operation course.
On a long-term storage of Cu-selective electrodes their
sensitivity essentially decreases owing to copper sulﬁ de
ageing, which results from enlargement of copper sulﬁ de
grains on the electrode surface and from the change of
the number of contacts between grains. One of the main
characteristics deﬁ ning the possibility of copper sulﬁ de
use as the ion-selective membrane is a hypermobility of
copper ions as compared to other ions of the membrane.
Dissolution of copper sulﬁ de can be used for changing
mobility of these ions in an ISE membrane prepared on
the basis of copper sulﬁ de.
The purpose of this work was to develop a restoration
method for Cu-selective electrodes, which have lost sen-
sitivity during storage. For this purpose we offer to carry
out a partial dissolution of a membrane surface layer,
in which processes of layer ageing and copper sulﬁ de
hydrolysis took place.
To reach the aim in view, we used donor-acceptor
electron-transport systems . On the contact with non-
aqueous solutions of organic ligands, copper sulﬁ des
form complex compounds soluble in an aprotic solvent
 that provided the demanded effect. An ISE membrane
was held in a salicylalaniline (SA) 0.1 M solution in N,N-
dimethyl formamide (DMF) within 16 h. After that the
membrane was washed out with acetone and dried up for
50 min at 50°С.
Acetone was puriﬁ ed as suggested in . N,N-Dimeth-
yl formamide was puriﬁ ed by vacuum distillation .
Salicylalaniline was obtained by condensation of salicylic
aldehyde with aniline. For this purpose 100 g of salicylic
aldehyde were dissolved in 250 ml of ethyl alcohol. The
reaction mixture was placed in a reﬂ ux ﬂ ask and heated
on a sand bath up to 356 K. A solution of freshly distilled
aniline (76.26 g) in ethyl alcohol (250 ml) was added