الفهرس 
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Abstract
The present thesis describes the preparation and determination of the
characteristic performance of screen printed electrodes for the possibility of rapid
in field analysis. These electrodes are utilized for the determination
surfactants such as dodecyltrimethylammonium bromide (DTAB), cetylpyridinium
chloride (CPC), and Septonex (1-(ethoxycarbonyl) pentadecyltrimethylammonium
bromide) in pharmaceutical preparations and sea water.
The electrode cocktail consists of paste composed of a mixture of graphite
powder (1-2 μm), plasticizer and binder. Potentiometric titrations of the surfactants
under investigation are based on ion pairs formation between the analytes and the
titrant materials (sodium tetraphenylborate (NaTPB), phosphotungstic acid (PTA),
phosphomolybdic acid (PMA), silicotungstic acid (STA) and ammonium reineckate
(RN) which has an opposite charge where precipitation of an ion pair of limited
solubility in water is observed. The thesis contains three chapters:
Chapter I
It includes introduction. General introduction concerning the theoretical
bases for preparation and uses of the different types of ion selective electrodes is
described. Focusing on screen-printed carbon paste electrode, as regards of methods
of preparation, general properties of screen-printed electrode and uses of this surface
electrode in the potentiometric titration of different species, is given.
Also, a literature survey on the different methods used for the determination
of dodecyltrimethylammonium bromide (DTAB), cetylpyridinium chloride (CPC)
and sodium dedecylsulphate (SDS) are discussed in details. These methods include
spectrophotometric, capillary electrophoresis, ion-selective, chromatographic,
polarographic and other miscellaneous methods. On screening literature survey, it
was obvious that no previous work has been done using screen printed electrodes for
the determination of surfactants except one publication given by the author.
SUMMARY
137
Chapter II
It contains full details for the preparation of all types of ion selective electrodes
specially the preparation of the screen-printed electrode and working procedures.
The analytical methods used to evaluate surface activity of specific materials,
evaluation of the electrode selectivity, determination of the studied surfactant in
pure solution and in some commercial preparations are also described.
Chapter III-V
Screen-printed ion-selective electrode for the determination of
cetylpyridinium chloride (CPC) is presented. These new electrodes involve in situ,
modified and unmodified screen-printed ion selective electrodes for the
determination of CPC.
For quantitative and qualitative composition, optimization of the developed
sensors (PVC, CPE and SPEs), an election scheme was followed. Both unmodified
(plain) electrodes and modified (in situ IP formation and modification with IP)
electrodes were prepared and tested for nature and content of modifier, type of
plasticizer, pH effect, response time and applications.
1. CP-ISEs modified with the IPs
1.1. Effect of the ion pair content
The influence of the CP-TPB content (sensing material) on the electrode
performance was studied. For this purpose, various electrodes were prepared
containing different amounts of the ion pair (5-20 mg for PVC, 5-30 mg for CPE,
and 5-30 mg for SPE). It was obvious from that, as the ion-pair content increases,
the slope of the calibration curve increases till certain point (optimum IP content is
found to be 15, 25 and 20 mg for PVC, CPE, and SPE, respectively) then decreases
for all types of the studied electrodes. This is also supported by the high slope
values of the calibration curve in the tested concentration range from 10-6-10-2 M
(55.90±0.99, 57.23±1.05 and 58.49±0.59 mV/decade for PVC, CPE, and SPE,
respectively)
SUMMARY
138
1.2. Effect of the ion pair type
Different fabricated electrodes (PVC, CPE, and SPEs) were modified in bulk
with different IPs; CP-TPB, -RN, -PTA, -PMA or -TSA as electroactive
components and conditioned in 10-3 M CPC solution for 24 h for PVC and CPE
electrodes. While for SPEs, for preconditioning for only 30 min before performing
the calibration process is done. The fabricated electrodes show Nernstian responses
towards CPC with different slopes depending on the nature of the IP used.
2. CP-ISEs modified with IPs in situ
2.1. Effect of the counter ion pair agent content
The effect of the counter ion-pair agent content on the performance of the
PVC, CPE, and SPE electrodes containing 5-25, 10-40, and 20-70 mg of NaTPB as
an ion pairing agent were studied. They were prepared and soaked in 10-2 mol L-1 of
CPC solution for 30 min. The result obtained showed that 7.5, 32, and 47 mg of
TPB contents gave the highest slope values of 64.34±2.16, 60.44±1.98, and
55.28±1.20 mV/decade for PVC, CPE, and SPE, respectively
2.2. Effect of the ion pairing agent type
Electrodes containing different ion pairing agents (TPB, RN, PTA, STA, and
PMA) were prepared, soaked in 10-2 mol L-1 of CPC for 30 min, and then used for
the determination of CPC.
3. CP-ISEs modified with ion pairs by soaking (Plain electrodes):
3.1. Effect of the plasticizer on soaked electrodes performance
The influence of the type of the plasticizer on the electrode performances has
been studied as the electrode plasticized with o-NPOE is compared with those of
TCP, DOP, DBP or DOS. The obtained calibration graphs with SPE using different
methods of preparation and different plasticizers clarified that, using of
o-NPOE as plasticizer showed the highest sensitivity of the membrane electrode
indicated with the highest slope and wider linear range specially with the soaked
electrodes.
SUMMARY
139
3.2. Effect of the IP solution type
Soaking of the unmodified PVC, CPE, and SPE electrodes in freshly
prepared IPs suspensions with TPB, RN, PTA, PMA, and STA is carried out where
they subsequently used for potentiometric measurements. It is obvious that the
electrodes soaked in the CP-TPB ion pair are found to have the highest sensitivity as
indicated by the highest slope values.
The mass production of disposable potentiometric strips using screenprinting
technology is described. The printed disposable electrodes strips containing
both the working are utilized as an end point indicator electrode for the
potentiometric titration of different surfactants in their pure solutions and different
samples. The fabrication of the potentiometric strips and the preparation of the
homemade printing carbon ink are described well. The factors affecting the
electrode performance are well presented and discussed in details in order to give
clear informations about screen printed technology.
The analytical performance of the obtained strips is compared with those for
CPE, and PVC electrodes using different modes of preparation (modified with IP,
modified in situ or soaked) were evaluated according to IUPAC recommendations.
The printed strips do not require any preconditioning before application in the
potentiometric titration of surfactants and have a very short response time reaching
3 seconds with adequate shelf time (6 months).
The influence of pH on the response of the PVC membrane CPE and SPE was
checked by recording the potential readings of the cell for solutions containing 10-4-
10-2 M of CPC at different pH values (pH 2-12) indicate that the response of the
electrodes was pH independent in the pH range 3.0-7.0, 3.0-8.0 and 3.0-8.0 for PVC,
CPE and SPEs, respectively.
The proposed disposable strips have been successfully used for the
potentiometric titration of the cationic surfactants in their analytical grad solutions,
pharmaceutical preparations and water samples with sensitivity comparable with the
different modes of preparation (modified with IP, modified in situ or soaked),
SUMMARY
140
official method and ability of field measurement with a portable potentiometric
titration system.
The SPEs modified in bulk with different IPs (septonex- TPB, -RN, -PTA, -
PMA or -STA) as electroactive components were prepared and conditioned in 10-3
mol L-1 of septonex solution. SPEs gave reproducible results after preconditioning
for only 30 min before performing the calibration process.
The influence of the type of the plasticizer on the electrode performances has
been studied as the electrode plasticized with o-NPOE is compared with those of
TCP, DOP, DBP or DOS. The obtained calibration graphs with SPE using different
plasticizers clarified that, using of o-NPOE as plasticizer showed the highest
sensitivity of the membrane electrode indicated with the highest slope