Synthesis of Macrocyclic Ionophore for the Development of Highly Selective Chloride Sensor

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ORIENTAL JOURNAL OF CHEMISTRY

An International Open Free Access, Peer Reviewed Research Journal

www.orientjchem.org

ISSN: 0970-020 X
CODEN: OJCHEG
2015, Vol. 31, No. (1):
Pg. 193-204

# Synthesis of Macrocyclic Ionophore for the Development of Highly Selective Chloride Sensor

SAMEENA MEHTAB* and TANVEER IRSHAD SIDDIQI

Department of Chemistry, Lovely Professional University, Punjab - 144806, India.

*Corresponding author E-mail: sameena.17937@lpu.co.in

http://dx.doi.org/10.13005/ojc/310121

(Received: January 10, 2015; Accepted: February 08, 2015)

ABSTRACT

The macrocyclic ligands 3,8,12,17-tetramethyl-2,18,9,11-bipyridyl-1,4,7,10,13,16hexaazacyclooctadecanetetrahydro bromide has been synthesized and explored as suitable
ionophores for chloride selective membrane sensors. It displays Nernstian behavior (59.2 mV
decade -1 ) across the range of 4.1 × 10 -8 to 1.0 × 10 -2 M. The detection limit of the electrode is ~ 15
nM and the response time and life times are 14 s and eight weeks respectively over a wide pH
range (3.5 - 9.5). Interference from other anions is very low and it can be used as indicator
electrode in the potentiometric titration of chloride ions and to determine chloride in agricultural soil
water samples.

Key words: Chloride Membrane Sensor; Ion-Selective Electrode; Macrocyclic Ionophore.

INTRODUCTION

The determination of the concentrations
of ionic species in aqueous samples is important in
many areas of applied analytical chemistry, e.g., in
process control, and in the analysis of clinical,
horticultural, or environmental samples. The ionselective electrodes are of widespread interest as
they provide a rapid, accurate, reproducible,
selective, and low-cost analytical method of specific
guests 1 . ISEs are also of obvious interest because

they can help translate the chemistry of new
substrate binding systems into tools that can be
used to recognize selectively various targeted
species in the presence of potentially interfering
analytes. Anions show a wide range of shapes and
geometries and a lot of them are pH-sensitive,
factors that have to be taken into account when
designing a specific anion host. Anion receptors
thus use binding forces that typically involve
hydrogen bonding, electrostatic interactions and
coordination to suitable metal centre. The effective

194 MEHTAB & SIDDIQI, _Orient. J. Chem.,_ Vol. 31 (1), 193-204 (2015)

anion-selective electrode should incorporate a
selective ionophore for a guest anion in its
membrane matrix 2 .

Among inorganic anions, Cl - anion is
particularly important as it plays an important role
in a variety of biological 3 and physiological
processes 4, clinical diagnosis 5, environmental
monitoring 6 and industrial applications 7-9 .
Furthermore, its metabolic imbalance in blood and
other body fluids results in various diseases and
pathological disorders such as stroke, edema, cystic
fibrosis, and atherosclerosis. With a continuous
emergence of numerous ionophores, great
progress has been made in the research in the direct
detection of chloride concentration and
potentiometric titration. As an electro active material
in an electrode, the ionophore plays a crucial role
in determining the performance characteristics of
ion selective sensors. Some anion exchangers 10,11

have been used as Cl - anion-selective ionophores
but often lacked selectivity toward Cl - anion over
other lipophilic anions such as NO3- and ClO4-. Lewis

other lipophilic anions such as NO3- and ClO4-. Lewis

acid macrocycles 12 and lanthanide tris(âdiketonates) have also been utilized to prepare Cl -

anion-selective electrodes that suffered from
significant interference from I -, Br, and SCN -

anions 13,14 . Several other strategies are followed to
design an ionophore with variety of functionalities
which can compliment with the shape and size of
an anion thereby showing selectivity towards a
particular anion, like, 2,5-dihydroxy-pbenzoquinone 15, Polypyrrole-graphite- epoxy
composite 16, Amino methylated polystyrene
salicylaldehyde schiff base Co(II) complex 17, Calix 4

arene derivative with ureido moiety 18,
Tridodecylmethyl ammonium chloride 19,20, hydrogen
bond forming ionophores 21,22, and epoxy resins 23 .
Though many species have been examined as
potential chloride ionophores, only few have yielded
requisite chloride selectivity to be used in the
preparation of membrane electrode.

For better performance the ionophore
ought to preferentially bind with the target ion and
should possess a high degree of its own
photochemical and redox stability. Therefore, it is
not surprising that the robust macrocycles and their
metal derivatives, due to their rich coordination
chemistry and structural diversity, have got much

- and ClO4

attention as ionophores for the selective recognition
and sensing of cations and anions 24-29 . They are
incorporated, as ion carrier agents, in suitable
polymeric membranes to get the ion selective
membrane electrodes. These electrodes respond
selectively to the concentration changes of a
particular cation or anion and thereby transduce
the analyte ion activity into a potential read-out.
Objective of the present paper is to synthesize a
new highly selective ionophore and to optimize
membrane compositions to achieve a chloride ion
sensor of improved response characteristics. The
3,8,12,17-Tetramethyl-2,18,9,11-Bipyridyl1,4,7,10,13,16-Hexaaza Cyclooctadecane
Tetrahydro bromide (Scheme. 1) represent a class
of macrocycle that should act as anion binding
agents 30,31 . In this anion-receptor interactions of
macrocyclic ionophore are expected to reflect
contributions from both electrostatic and hydrogen
bonding interactions in varying degrees depending
on the conditions ( _e.g_ ., degree of protonation, nature
of solvent, _etc._ ) Because of this potential duality, it
was proposed that studies of appropriately chosen
analytes, capable of multiple types of
supramolecular interactions, would provide
invaluable insights into the fundamental molecular
recognition properties of this class of receptor.

EXPERIMENTAL

Reagents

Reagent grade hexadecyl
trimethylammonium bromide (HTAB),
dibutylphthalate (DBP), benzyl acetate (BA),
dioctylphthalate (DOP), tributyl phosphate (TBP),
dioctyl phthalate (DOP), _o_ -nitrophenyloctyl ether ( _o_ NPOE), tetrahydrofuran (THF), barium chloride
dihydrate (BaCl 2.2H 2O) sodium borohydride
(NaBH4), ethylenediamine, hydrobromic acid, and
high molecular weight poly(vinylchloride) were
purchased from E. Merck (Germany) and used as
received. 2,6-Diacetylpyridine and methylacrylate
acrylonitrile were procured from S. D. Fine-chem.
Ltd. Sodium salts of all anions used were of analytical
grade and used without any further purification. The
solutions of anion salts were prepared in milliipore
water and standardized whenever necessary.

Apparatus

Carbon, hydrogen, and nitrogen were

MEHTAB & SIDDIQI, _Orient. J. Chem.,_ Vol. 31 (1), 193-204 (2015) 195

analyzed with a Vario EL III elemental analyzer after
carefully dried samples under vacuum for several
hours. The UV–Vis spectra were recorded on Perkin–
Elmer Lambda 35 UV/Vis spectrophotometer. IR
spectra were obtained on a Thermo Nikolet Nexus
FT-IR spectrometer in KBr. Room temperature
magnetic susceptibility measurements were done
on a Princeton applied research vibrating sample
magnetometer Model. All potential measurements
were performed at ambient temperature using a
Century scientific-digital pH/ millivolt-meter.

Synthesis and Characterization of 3,8,12,17-
Tetramethyl-2,18,9,11-Bipyridyl-1,4,7,10,13,16-
Hexaaza Cyclooctadecane Tetrahydrobromide
as Macrocyclic Ionophore

To synthesize macrocyclic ionophore (MI)
using well established 2+2 template condensation
method, followed by NaBH4 reduction of the imine
as shown in the scheme 1. Ba(II) was chosen as
the templating ion due to its success in promoting
template condensation of macrocycles of this ring
size. This adaption of the synthetic scheme is yield
optimized (65%) and convenient in that
condensation and the reduction step was
performed in situ. A solution of ethylene diamine
(0.5 mL, 7.5 mmol) in a minimum amount of
methanol (10 mL) was added drop wise over 15
minutes to the stirred solution of 2,6-diacetyl
pyridine (1.224 g, 7.5 mmol) and BaCl2.2H2O (0.915
g, 3.75 mmol). The mixture was refluxed for 12 h.
Yellow solution was allowed to cool to room
temperature. Solid NaBH4 (0.751 g, 20 mmol) was
added slowly and the flask was placed in an ice
bath and was stirred for 15 minutes. A second
addition of NaBH4 (0.375 g, 10 mmol) was done
and the resulting yellow-white mixture was stirred
at room temperature for one hour. Evaporation of
solvent under reduced pressure yielded a yellowwhite product, which was extracted with
dichloromethane (DCM). Evaporation of combined
extracts to dryness yielded orange oil. This oil was
dissolved in 20 mL of methanol, and 48 %
hydrobromic acid (about 6 mL) was added until pH
paper tested strongly acidic.

The product was recrystallised by
dissolving in a minimum amount of hot water to
which was added a small amount of activated
carbon. After the mixture was filtered, absolute

ethanol was added to incipient cloudiness while
the heating and stirring were maintained. The
solution was cooled to room temperature and
placed in a refrigerator for two days. The white
crystalline solid (MI) was washed with ice cold
ethanol and stored in a vacuum desiccators. Yield
46 %; M.P. > 300 0 C; color white crystalline solid,
reaction time 12 h; Anal. Calcd for C22H38Br4N6: C,
37.42; H, 5.42; Br, 45.26; N, 11.90. Found: C, 37.25;
H, 5.49; N, 11.82. IR (KBr, cm -1 )  max: 3732, 2351,
2324, 1824, 1740, 1615, 1442, 1155, 1021 cm -1 ; 1 H
NMR (CDCl3, TMS,  ppm, 500 MHz): 7.882 (t, 2H),
7.428 (d, 4H), 1.580 (s, 12H), 3.404 (qt, 8H), 4.698
(m, 4 H); 13 C NMR (CDCl3,  ppm, 500 MHz): 14.53,
40.29, 57.37, 120.85, 139.07, 153.26; UV-Visble:
202, 260 nm.

Preparation of Membranes

In the present work ion sensitive
membranes of the PVC matrix were fabricated
according to the procedure described by Craggs _et_
_al._ 32 . An important requirement for making PVC
membranes of an ion selective sensor is that the
ionophore, PVC and plasticizers and anionic
additives should be soluble in some fast
evaporating solvent. The ionophores, PVC, different
plasticizers and anionic additives used in the
present investigations were found to be sufficiently
soluble in THF. Therefore, the solvent THF was used
for preparing membranes. Thus, membrane
cocktails were formulated by dissolving appropriate
amounts of ionophores, anionic additives and
plasticizers. The components were added in terms
of weight percentages. After thorough dissolution,
the homogeneous mixture was concentrated by
evaporating THF and it was then poured into
polyacrylates rings placed on a smooth glass plate.
The solution should be poured gently so that
bubbles are not formed. A pad of filter papers and a
heavy weight are then placed on top of the ring and
the assembly was left for one day to allow the
tetrahydrofuran to evaporate slowly at room
temperature. After 24 hours of evaporation, the
transparent membranes of 0.4 mm thickness were
removed carefully from the glass plate and glued
to one end of pyrex glass tube. It is known that the
sensitivity, linearity and selectivity of ion selective
sensor depend significantly on the membrane
composition. Thus, optimization was performed after
a good deal of experimentation to provide

196 MEHTAB & SIDDIQI, _Orient. J. Chem.,_ Vol. 31 (1), 193-204 (2015)

membranes, which generate reproducible and
stable potentials. The membranes having only PVC
as membrane ingredient (dummy membranes)
have also been prepared to observe whether any
background potentials being produced due to
binding material or not.

Preparation of Sandwich Membranes

Ion-selective electrode membranes were
cast from above mentioned procedure. The blank
membranes (without ionophore) were also
prepared having same composition. The sandwich
membrane was made by pressing two individual
membranes (ordinarily one without ionophore and
one with the same components and an additional
ionophore) together immediately after blotting them
individually dry with tissue paper. The obtained
sandwich membrane was visibly checked for air
bubbles before mounting in electrode body with the
ionophore-containing segment facing the sample
solution. The combined segmented membrane was
then rapidly mounted on to the electrode body and
immediately measured 33,34 .

Potential Measurement

For the determination of chloride ion,
membranes were equilibrated for 48 h in 0.01 M of
NaCl solutions. The performance of the electrode

was investigated by measuring its potential in NaCl
solutions in the concentration range 1.0 ´ 10 -9 - 1.0 ´
10 -2 M. Small concentrations of NaCl was obtained
by gradual dilution of 0.01 M NaCl solution with
millipore water. The potential measurements were
carried out at 25 ± 1 o C using following cell
assemblies:

Ag/AgCl | KCl(satd) | test solution || PVC
membrane || 0.01 M NaCl | Hg/Hg2Cl2 | KCl(satd)

RESULTS AND DISCUSSION

Response of Different Anions

In preliminary experiments, various PVCmembrane ion-selective electrodes with the
synthesized macrocyclic ionophore (MI) were
prepared and tested for different anions. The
potential response of the electrodes based on MI
for different anions are shown in Fig 1. The results
exhibited significantly high selectivity to chloride ion
over other anions. Hence, the macrocyclic ionophore
(MI) was selected as a carrier for preparation of
chloride sensor.

The Effect of Membrane Composition on Potential
Response of the Chloride Sensor

Potential of the membranes of MI

Table 1: Potentiometric response characteristics of chloride membrane sensors based on ionophore MI

Sensor Composition of Sensor Membrane (w/w, %) Slope(mV Linear Range (M)

No. Ionophore HTAB Plasticizer PVC decade -1

(MI) of activity)

1 0 4 56, DBP 40 38.4 4.1×10 -4 -1.0×10 -2

2 12 0 54, DBP 34 53.8 4.0×10 -6 -1.0×10 -2

3 12 4 0 84 49.5 6.3×10 -4 - 1.0×10 -2

4 12 4 54, _o-_ NPOE 30 65.3 8.8×10 -5 - 1.0×10 -2

5 12 4 54, DOP 30 58.0 6.6×10 -7 - 1.0×10 -2

6 12 4 54, BA 30 55.4 8.2×10 -5 - 1.0×10 -2

7 12 4 54, TBP 30 57.2 1.9×10 -5 - 1.0×10 -2

8 12 8 50, DOP 32 59.8 7.4×10 -7 - 1.0×10 -2

9 12 2 54, DOP 32 57.4 1.4×10 -6 - 1.0×10 -2

10 12 6 44, DOP 40 59.5 1.7×10 -7 - 1.0×10 -2

11 10 4 54, DOP 32 59.2 4.1×10 -8 - 1.0×10 -2

12 8 4 54, DOP 34 58.2 7.5×10 -7 - 1.0×10 -2

13 14 4 52, DOP 30 58.8 1.2×10 -7 - 1.0×10 -2

MEHTAB & SIDDIQI, _Orient. J. Chem.,_ Vol. 31 (1), 193-204 (2015) 197

investigated as a function of chloride ion activity in
the range 1.0 × 10 -9 to 1.0 × 10 -2 M and the results
obtained are compiled in Table 1. The electrodes

Table 2. Selectivity coefficients of chloride selective
sensor no. 11 based on the membranes of (MI)

Interfering Selectivity Coefficient (-log)K _pot_ _Cl,B_

Ion (B) (MPM) (FIM)
Sensor No. 11 Sensor No. 11

with no carrier (containing PVC, plasticizer and
HTAB) displayed insignificant sensitivity towards
chloride. The influence of plasticizer on the
response characteristics of the chloride electrodes
was investigated by using five plasticizers of
different polarities including DBP, _o-_ NPOE, DOP,
BA and TBP. The sensor no. 3 having membrane
without plasticizer exhibits a narrow working
concentration range of 10 -4 to 10 -2 M with a sub
Nernstian slope. Improvement in sensors
performance was observed by the addition of
plasticizer. Among the several membranes tested
for each of the carriers, the membranes
incorporating DOP showed better potentiometric
responses, i.e., higher sensitivity and wider linearity
of the calibration plots (sensor no. 11, Table 1).

The addition of lipophilic cationic additive
in anion selective membranes is necessary to
introduce perm selectivity. The influence and
concentration of the membrane additives was also
investigated by incorporating HTAB into the
membranes. The potentiometric sensitivity of the
membranes based on both carriers was greatly
improved in the presence of HTAB as a lipophilic
cationic additive, compared to the membranes with
no additive at all. Previous studies have shown that

SCN - 2.81 2.65
NO2- 3.12 3.05

NO2- 3.12 3.05

I - 3.27 3.08
F - 3.28 3.83
Br - 3.55 5.38
CH3COO - 3.63 3.55
NO3- 3.70 3.51

NO3- 3.70 3.51

OH - 3.93 3.82
HCO3- 4.19 4.08

HCO3- 4.19 4.08

CN - 4.24 4.41
HPO42- 4.52 4.20

HPO42- 4.52 4.20

Sal - 4.62 4.98
Cit 3- 4.96 4.87
SO42- 5.14 5.18

SO42- 5.14 5.18

C2O42- 5.18 5.02

ClO4- 5.20 5.11

- 5.20 5.11

Table 3: Formation constant values of various ions for Cl ” selective membrane based on [MI]

Interfering Ions Formation Constant(log  IL _n_ ) Interfering Ions Formation Constant(log  IL _n_ )

Cl - 8.25 F - 2.28
NO3- 4.95 OH - 4.08

NO3- 4.95 OH - 4.08

HPO42- 3.11 Br - 5.00

Cit 3- 2.43 SO42- 2.05

HCO3- 3.62 SCN — 5.08

CH3COO - 4.66 CN - 3.28
C2O42- 2.85 Sal - 4.25

C2O42- 2.85 Sal - 4.25

I - 5.12 ClO4- 2.07

- 2.07

Table 4: Potentiometric determination of chloride
ion in soil water samples (mean ± S.D., _n_ = 3)

Added (mg/L) Found (mg/L) % Recovery

250 236±0.3 94.4
500 481±0.7 96.2
1000 973±1.0 97.3

there is an optimal concentration of lipophilic ionic
additives in the membranes and that gives the best
electrode performance 35 . The effect of HTAB
concentration in the membrane was investigated
at several additive/ionophore mole ratios. The
sensors with HTAB/MI mole ratios of ~ 0.55 for both
of the carriers exhibited maximum sensitivity over
a wide range of chloride concentration.

198 MEHTAB & SIDDIQI, _Orient. J. Chem.,_ Vol. 31 (1), 193-204 (2015)

MEHTAB & SIDDIQI, _Orient. J. Chem.,_ Vol. 31 (1), 193-204 (2015) 199

200 MEHTAB & SIDDIQI, _Orient. J. Chem.,_ Vol. 31 (1), 193-204 (2015)

The Dynamic Response Time and Life Time of the
Proposed Electrode

Dynamic response time is an important
factor for chloride sensitive sensors. In this study,
the practical response time has been recorded (for
sensor no. 11) by changing solutions with different
Cl - concentrations. The measurement sequence
was from the lower (1.0 × 10 "8 M) to the higher (1.0
×10 "2 M) concentration. The resulting data shows
that the time needed to reach a potential with in ±
1.0 mV of the final equilibrium value after successive

immersion of a series of Cl - solution, each having a
tenfold difference in concentration is only 14 s.

To evaluate the reversibility of the
electrode, a similar procedure in the opposite
direction was adopted. The measurements have
been performed in the sequence of high-to-low from
(1.0 × 10 -2 - 1.0 × 10 -6 M) sample concentrations. The
results showed that, the potentiometric response of
the electrodes was reversible; although the time
needed to reach equilibrium values (34 s) was

Scheme 1: Synthesis of macrocyclic ionophore (MI)

Fig. 1: Potential responses of ion-selective
membrane sensor based MI for various anions

*(Sal - is salicylate and Cit 3- is citrate)

Fig. 2: Calibration plot of chloride-selective

sensors based on MI ionophore

MEHTAB & SIDDIQI, _Orient. J. Chem.,_ Vol. 31 (1), 193-204 (2015) 201

Fig. 3: Effect of pH on potential response

of the chloride ion-selective sensors

longer than that of low-to high sample
concentrations. The life time of proposed sensor is
around eight weeks as potentiometric
characteristics of the sensor remain almost
constant with in this period of time.

Calibration Characteristics

Among the different membrane
compositions, membranes with MI/HTAB/DOP/PVC
in (w/w, %) 10/4/54/32 showed highest sensitivity
and widest linear range and were selected as the
optimum composition for further studies (Fig. 2).
These sensors exhibit the maximum working
concentration range of 4.1 × 10 -8 to 1.0 × 10 -2 M,
detection limit 1.5 × 10 -8 M with a slope of 59.2 ± 0.2
mVdecade -1 of activity (Sensor no. 11, Table 1).
Repeated monitoring of potentials and calibration,
using the same electrode over several days gave
good slope reproducibility; the standard deviation
(S.D.) of slope was 0.2 mV decade -1 activity (N=3).

The influence of pH on electrode’s parameters

The pH dependence of the electrode
potential was investigated in over the pH range of
1-12 for 10 -2 M, 10 -3 M and 10 -4 M of Cl – ion solutions.
The potentiometric response of the chloride sensor
was found to be sensitive to pH changes. pH was
adjusted by the addition of 0.01 M nitric acid and
sodium hydroxide. The results given in Fig. 3 show
that the potential response remains constant over
the pH range ~3.5 - 9.5 and the same can be taken
as the working pH range of the electrode. The

Fig. 4: Potentiometric titration curve for 20 mL

of 1.0 × 10 -4 M NaCl with 1.0 × 10 -3 M AgNO3

using the proposed sensor (no. 11)

significant change in potential response observed
at a deviation at pH values < 3.5, can be due to
simultaneous response of the electrode to the
oppositely charged H 3O + and Cl – ions. The
contribution of H 3O + to potential response
counteracts that of Cl – ions. The observed potential
drift at high pH values could be due to response of
sensor to OH - ions.

Anions Effect on Sensor Selectivity

Selectivity is an important characteristic
of a sensor that delineates the extent to which the
device may be used in the estimation of analyte ion
in the presence of other ions and extent of utility of
any sensor in real sample measurement. In this
work, the selectivity coefficients of the sensors
toward different anionic species (A n- ) were
evaluated by using both the matched potential
method (MPM) 36,37 and the fixed interference method
(FIM) 38 .

_Cl,B_ _aB_ _a_

_aCl_  _a'Cl_  _a_

_aB_ _aB_

_B_

In the MPM, the selectivity coefficient
( _KClPot_, _B_ ) was determined by measuring the change

_Pot_

( _KClPot_, _B_ ) was determined by measuring the change

in potential upon increasing the primary ion (Cl - )
activity from an initial value of _a_ Cl to  _´_ Cl and _a_ B
represents the activity of interfering ion added to
the reference solution of primary ion of activity _a_ Cl
which also brings about same potential change. It
is given by expression:

_K_ _Cl,potB_  Δ _aCl_  _a'Cl_ 

...(1)

_pot_ _Cl_

_Cl_ _Cl_

_B_

202 MEHTAB & SIDDIQI, _Orient. J. Chem.,_ Vol. 31 (1), 193-204 (2015)

In the present studies _a_ Cl and _a´_ Cl were kept
at 1.0 × 10 -4 and 1.0 × 10 -3 M Cl - and _a_ B was
experimentally determined. FIM is the most widely
used procedure as per IUPAC recommendation for
determining selectivity coefficients 39 . In the FIM, the
selectivity coefficient was evaluated from potential
measurement on solutions containing a fixed
concentration of interfering ion (1.0 × 10 -2 M) and
varying amount of Cl - ions. The values of selectivity
coefficient so determined are compiled in Table 2.
A value of selectivity coefficient equal or greater
than to 1.0 indicates equal response to both primary
ion and interfering ions. A value smaller than 1.0
shows that the sensor is selective to the primary
ion over the interfering ion. It is seen from the Table
2, that the selectivity coefficients determined by both
the methods are sufficiently smaller than 1.0
indicating that the present sensors are significantly
selective to chloride ion over all the interfering ions.
Most of the interfering ions showed low values of
selectivity coefficients (~ 10 -3 - 10 -4 ), indicating no
or minimum interference in the performance of the
electrode assembly.

Determination of Formation Constant

Formation constant of the ion–ionophore
complex within the membrane phase is a very
important parameter that dictates the practical
selectivity of the sensor. In this method, two
membrane segments are fused together, with only
one containing the ionophore, to give a
concentration-polarized sandwich membrane. A
membrane potential measurement of this transient
condition reveals the ion activity ratio at both
interfaces, which translates into the apparent
binding constants of the ion-ionophore complex 40 .
In this method complex formation constants
obtained by neglecting ion pairing because ionpairing effects are relatively nonspecific _i.e_, all ion
pair formation constants have approximately the
same value. As reported, the membrane potential
_E_ M is determined by subtracting the cell potential
for a membrane without ionophore from that for the
sandwich membrane. The formation constant is then
calculated from the following equation 2:


   _LT_ 

  _LT_  _nRT_  

 _Z_ _I_ 



_n_

_LT_  _nRT_   exp  _EM_ _zI_ _F_
_Z_ _I_   _RT_

 _ILn_    _LT_  _nRT_   exp  _EM_ _zI_ _F_  ...(2)

_Z_ _RT_

Where _L_ T is the total concentration of
ionophore in the membrane segment, _R_ T is the
concentration of lipophilic ionic site additives, _n_ is
the ion-ionophore complex stoichiometry, and _R_, _T_
and _F_ are the gas constant, the absolute
temperature, and the Faraday constant. The ion
carries a charge of _z_ I. The determined formation
constants (log  IL _n_ ) for the examined different
complexes were recorded in Table 3. The elapsed
time between sandwich fusion and exposure to
electrolyte was typically <1 min. The potential was
recorded as the mean of the last minute of a 5 min
measurement period in the appropriate salt solution.
The potential of such sandwich membranes
remains free of diffusion-induced potential drifts for
about 20 min. Standard deviations were obtained
based on the measurements of sets of at least three
replicate membrane disks that were made from the
same parent membrane. A careful analysis of the
data in Table 3 reveals that chloride ion has
significant anion-binding characteristics.

Analytical Applications

The proposed chloride membrane sensor
(no. 11) was found to work well under laboratory
conditions. It was applied successfully as an
indicator electrode in the potentiometric titration of
20 mL of 1.0 × 10 -4 M NaCl with 1.0 × 10 -3 M AgNO3
and the resulting titration curve are shown in Fig 4.
As can be seen, the amount of chloride can be
determined with sensor.

The analytical utility and sensitivity of the
proposed membrane sensor was verified by
analysis of Cl - ion from soil water samples. Four
basic factors determine the amount of Cl - available
to crops growing in well drained soils, the Cl -

concentration in the soil solution; atmospheric
deposition of Cl - ; the Cl - concentration in the
irrigation water; and the content of Cl - in fertilizers
and manure. As a result of their genetic
characteristics, crops have different requirements
and tolerance to Cl - . The amount of Cl - added to a
field via the irrigation water (fresh or treated
municipal effluents) depends on farm activities.
Water of low to medium salinity contains 100 - 300
g Cl - m -3, whereas saline water contains 300 - 1200
g Cl - m -3(41-44) .

The direct potentiometric measurement

_I_

  exp  _EM_ _zI_ _F_ 

  _RT_ 

_RT_

MEHTAB & SIDDIQI, _Orient. J. Chem.,_ Vol. 31 (1), 193-204 (2015) 203

was carried out using standard addition technique,
where recovery percentage in the range 94.4 - 97.3.
The result obtained for the determination of chloride
ion at several concentrations is in close agreement
with the known chloride content as given in Table 4.
Recovery experiments were performed by repeated
measurements (n = 3) of soil water samples
containing various amounts of chloride ions.

CONCLUSIONS

We synthesize a new macrocycle as anionrecognizing ionophore 3,8,12,17-Tetramethyl2,18,9,11-Bipyridyl-1,4,7,10,13,16-Hexaaza
Cyclooctadecane Tetrahydrobromide for the
fabrication of potentiometric membrane and fully
characterize the potentiometric performances of
selective chloride ion membrane sensor. The
proposed macrocylcic ionophore is found to be very
useful in ISE membranes for chloride determination.

Compared with earlier sensors, the new ISE for Cl -

shows advantages as to stability, lower detection
limit, high pH range and good selectivity. Fast
response and a reasonable long-term stability to
chloride ions characterize the proposed electrode.
On the basis of their selectivities, this sensor is
expected to be adequate for the environmental
water monitoring. Present sensor no. 11 was
compared with some reported chloride selective
sensors (Table 5). It is seen that the selectivity,
working concentration range and pH range of the
proposed sensor toward chloride is better as
compared to reported sensors.

ACKNOWLEDGEMENTS

Dr. Sameena Mehtab and Dr. Tanveer
Irshad Siddiqi are grateful to Council of Scientific
and Industrial Research, New Delhi, India for
providing financial assistance for this work.

REFERENCES

1. Morf, W. E.; The Principles and Ion-selective
Electrodes and Membrane Transport,
Elsevier, Amsterdam 1981 .
2. Bakker, E.; Buhlmann, P.; Pretsch, E. _Chem._
_Rev._ 1997, _97_, 3083-3132
3. Oka, S.; Sibaraki, Y.; Tahara, S. _Anal. Chem._
1991, _53_, 588-593
4. Seiler, H. G.; Sigel, H.; Sigel, A.; Handbook
on Toxicity of Inorganic Compounds; Dekker:
New York 1988 .
5. Huber, C.; Werner, T.; Krause, C.; Klimant, I.;
Wolfbeis, O. S. _Anal. Chim. Acta_ 1998, _364_,
143-151
6. Martin, A.; Narayanaswamy, R. _Sens._
_Actuators B_ 1997, _39,_ 330-333
7. Badr, I. H. A.; Diaz, M.; Hawthorne, M. F.;
Bachas, L. G. _Anal. Chem._ 1999 _, 71_, 13711377
8. Geddes, C. D. _Sens. Actuators B_ 2001, _72_ ,
188-195
9. Ashcroft, F. M. _Ion Channels and Diseases_,
Academic Press: San Diego, C A, 2000
10. Oka, S.; Sibazaki, Y.; Tahara, S. _Anal. Chem._
1981, _53_, 588-593
11. Ozawa, S.; Miyag, H.; Shibata, Y.; Oki, N.;
Kunitake, T.; Keller, W. E. _Anal. Chem._ 1996 _,_

_68_ , 4149-4152
12. Badr, I. H. A.; Diaz, M.; Hawthorne, M. F.;
Bachas, L. G. _Anal. Chem._ 1999, _71_, 13711377
13. Dzhabarov, V. I.; Knyazev, A. A.; Yu, G. G.
Russian, _J. Appl. Chem._ 2006, _79_, 18161819
14. Mahajan, R. K.; Kaur, I. K. R.; Onimaru, A.;
Shinoda, S.; Tsukube, H. _Anal. Chem._ 2004,
_76,_ 7354-7359
15. Sundaram, R.; Hariprasad, K. S. _Ind J. Chem._
_Soc._ 2007, _14_ , 451-456
16. lvarez-Romero, G. A.; Ramrez-Silva, M. T.;
Galan-Vidal, C.A.; Paez-Hernandez, M. E.;
Romero-Romoc, M. A. _Electroanalysis_ 2010,
_22_ ; 1650-1654
17. Kumar, K. G.; John, K. S.; Indra, C. J. _Ind J._
_Chem. Soc._ 2006, _13_ , 13-17
18. Babu, J. N.; Bhalla, V.; Kumar, M.; Mahajan,
R. K.; Puri, R. K. _Tetrahedron Letters_ 2008 _,_
_49_, 2772-2775
19. Legin, A.; Makarychev-Mikhailov, S.;
Kirsanov, D.; Mortensen, J.; Vlasov, Y. _Anal._
_Chim. Acta_ 2004, _514_, 107-113
20. Lyczewska, M.; Wojciechowski, M.; Bulska,
E.; Elizabeth, A. H.; Hall, K.; Maksymiuk, A.;

204 MEHTAB & SIDDIQI, _Orient. J. Chem.,_ Vol. 31 (1), 193-204 (2015)

Michalska, _Electroanalysis_ 2007, _19_, 393397
21. Xiao, K. P.; Bühlmann, P.; Nishizawa, S.;
Amemiya, S.; Umezawa, Y. _Anal._
_Chem._ 1997, _69_ , 1038-1044
22. Gupta, V. K.; Goyal, R. N.; Sharma, R. A.
_Electrochim. Acta_ 2009, _54_, 4126-4132
23. Shin, J. H.; Lee, H. L.; Cho, S. H.; Ha, J.; Nam,
H.; Cha, G. S. _Anal. Chem._ 2004, _76_, 42174222
24. Singh, A. K.; Mehtab, S.; Saxena, P. _Talanta_,
2006, _69_ ; 1143-1148
25. Kumar, A.; Mehtab, S.; Singh, U. P.; Aggarwal,
V.; Singh, J. _Electroanalysis,_ 2008, _20_ , 11861193
26. Simonneaux, G.; Maux, P. L. _Coord. Chem._
_Rev._ 2002, _228_ , 43-60
27. Biesaga, M.; Pyrzynska, K.; Trojanowicz, M.
_Talanta_ 2000 _,_ _51_, 209-224
28. Chou, J. H.; Kosal, M. E.; Nalwa, H. S.; Rakow,
N. A.; Suslick, K. S.; Kadish, K.; Smith, K.;
Guilard R. (Eds.), The Porphyrin Handbook,
Vol. VI; Academic Press, New York, 2000
29. Purrello, R.; Gurrieri, S.; Lauceri, R. Coord.
_Chem. Rev._ 1999, _190_ , 683-706
30. Fibbioli, M.; Berger, M.; Schmidtchen, F. P.;
Pretsch, E. _Anal. Chem._ 2000, _72_ , 156-160
31. Beer, P. D.; Schmitt, P. _Curr. Bio. Chem. Bio._

1997, _1_ , 475-482
32. Craggs, A.; Keil, L.; Moody, G.J.; Thomas, J.
D. R. _Talanta_ 1975 _, 22_, 907-910
33. Mi, Y.; Bakker, E. _Anal. Chem._ 1999, _71_, 52795287
34. Perez, M. A.; Marin, L. P.; Quintana, J. C.;
Pedram, M. Y. _Sens. Actuators B_, 2003, _89_,
262-268
35. Schaller, U.; Bakker, E.; Spichiger, U. E.;
Pretsch E. _Anal. Chem._ 1994, _66_, 391-398
36. Umezawa, Y.; Umezawa, K.; Sato, H. _Pure_
_Appl. Chem._ 1995, _67,_ 507-518
37. Gadzekpo, V. P. Y.; Christian, G. D. _Anal. Chim._
_Acta_ 1984, _164,_ 279-282
38. Bakker, E.; Pretsch, E.; Bühlmann, P.; _Anal._
_Chem._ 2000, _72,_ 1127-1133
39. Viteri, F. J. S.; Diamond, D. _Analyst,_ 1994,
_119,_ 749-758
40. Shultz, M. M.; Stefanova, O. K.; Mokrov, S. B.;
Mikhelson, K. N. _Anal. Chem._ 2002, _74,_ 510517
41. Goos, R. J. _Crops Soils_ 1987, _39_, 12-13
42. LaCroix, R. L.; Keeney, D. R.; Walsh, L. M.
_Commun. Soil Sci. Plant Anal.,_ 1970, _1,_ 1-6
43. Narayanan, P. N. V. Handbook of Ammonium
Chloride Fertilizer, McMillan, India, 1990
44. Krieg, D. R.; Sung, D. _Commun. Soil Sci. Plant_
_Anal._ 1977, _8,_ 109-114.

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