Fatehy M. Abdel-Haleem

Molecularly imprinted polymer-based bulk optode for the determination of itopride hydrochloride in physiological fluids

We report here for the first time on the use of Molecularly Imprinted Polymers as modifiers in bulk optodes, Miptode, for the determination of a pharmaceutical compound, itopride hydrochloride as an example in a concentration range of 1×10(-1)-1×10(-4)molL(-1). In comparison to the optode containing the ion exchanger only (Miptode 3), the optode containing the ion exchanger and the MIP particles (Miptode 2) showed improved selectivity over the most lipophilic species, Na(+) and K(+), by more than two orders of magnitude. For instance, the optical selectivity coefficients using Miptode 2, [Formula: see text] , were as follow: NH4(+)˂-6; Na(+)=-4.0, which were greatly enhanced in comparison with that obtained by Miptode 3. This work opens a new avenue for using miptodes for the determination of all the pharmaceutical preparations without the need for the development of new ionophores.

PVC membrane, coated-wire, and carbon-paste ion-selective electrodes for potentiometric determination of galantamine hydrobromide in physiological fluids

We report on highly-sensitive ion-selective electrodes (ISEs) for potentiometric determining of galantamine hydrobromide (GB) in physiological fluids. Galantamine hydrobromide (GB) was selected for this study due to its previous medical importance for treating Alzheimers disease. Three different types of ISEs were investigated: PVC membrane electrode (PVCE), carbon-paste electrode (CPE), and coated-wire electrode (CWE). In the construction of these electrodes, galantaminium-reineckate (GR) ion-pair was used as a sensing species for GB in solutions. The modified carbon-paste electrode (MCPE) was prepared using graphene oxide (MCPE-GO) and sodium tetrakis (trifluoromethyl) phenyl borate (MCPE-STFPB) as ion-exchanger. The potentiometric modified CPEs (MCPE-GO and MCPE-STFPB) show an improved performance in term of Nernstian slope, selectivity, response time, and response stability compared to the unmodified CPE. The prepared electrodes PVCE, CWE, CPE, MCPE-GO and MCPE-STFPB show Nernstian slopes of 59.9, 59.5, 58.1, 58.3 and 57.0 mV/conc. decade, and detection limits of 5.0 × 10-6, 6.3 × 10-6, 8.0 × 10-6, 6.0 × 10-6 and 8.0 × 10-6 mol L-1, respectively. The prepared ISEs also show high selectivity against cations (i.e. Na+, K+, NH4+, Ca2+, Al3+, Fe3+), amino acids (i.e. glycine, L-alanine alanine), and sugars (i.e. fructose, glucose, maltose, lactose). The prepared ISEs are applicable for determining GB in spiked serums, urines, and pharmaceutical preparations, using a standard addition and a direct potentiometric method. The fast response time (<10 s), long lifetime (1-5 weeks), reversibility and stability of the measured signals facilitate the application of these sensors for routine analysis of the real samples.

Calixarene-doped PVC polymeric films as size-selective optical sensors: Monitoring of salicylate in real samples

Preparation of novel salicylate-selective optical sensors (bulk optodes) was performed and applied successfully for salicylate determination in pharmaceutical formulations, Aspirin® and Aspocid®. t-butyl calix[4]arene ionophore was incorporated in a plasticized poly (vinyl-chloride) membrane containing the chromoionophore ETH5294 (O1) or ETH7075 (O5). The optical response to salicylate was due to size-selective extraction of salicylate from the aqueous solution to the optode bulk through formation of hydrogen bond accompanied by chromoionophore protonation, that resulted in the optical response at 680 or 540 nm for O1 or O5, respectively. Reliable size-selectivity was measured for salicylate over other anions; The calculated selectivity coefficients of O5 optode were found to be: -4.4, -2.0 and - 3.7 for iodide, benzoate and perchlorate, respectively. The hydrogen bonding mechanism and selectivity pattern were ensured and explained by IR and 1H NMR spectroscopy. For the same purpose, a molecular recognition constant of βsal=100.043 was calculated using sandwich membrane method, and its small value ensured that hydrogen bonding interaction is responsible for the optode response. The detection limits of O1 and O5 in salicylate buffered solutions were 9.0 × 10-5 and 8.9 × 10-5 M with response times of 5 and 3 min, respectively, and with very good reversibility. The practical utility of the developed sensors was ensured by salicylate determination in Aspirin® and Aspocid®. Beyond the observed analytical performance, the present work aims not only to effectively apply Calixarene without derivatization, but also to estimate the strength of the size-dependent hydrogen bonding and comprehensively study the interaction mechanism.

Electrochemical Detection of the Different Species of Levofloxacin Using PVC, Carbon Paste and Screen-Printed Electrodes: Effect of pH

The zwitterionic compound, levofloxacin, was determined for the first time at different pH values in pure samples, pharmaceutical preparations and spiked serum and urine samples. Different types of potentiometric sensors including poly (vinyl chloride) membrane electrode, carbon paste electrode and screen printed electrode, containing the ion pair levofloxacinium-phosphomolybdate as the electroactaive species, were used for this purpose. The effect of pH is the key factor in determining the ratio of the different species that can exist in the medium (zwitterionic, monocationic, dicationic, anionic and neutral), and so it is the controller of the electrochemical performance. The different sensors were fully characterized and optimized in terms of composition, pH effect, selectivity, response and lifetimes. The different sensors showed reliable reversibility and could be utilized for the determination of the drug in real spiked physiological fluids with reliable recovery values.

Highly selective thiocyanate optochemical sensor based on manganese(III)-salophen ionophore

We report on the development of optochemical sensor based on Mn(III)-salophen ionophore. The sensor was prepared by embedding the ionophore in a plasticized poly (vinyl chloride) impregnated with the chromoionophore ETH7075. Optical response to thiocyanate occurred due to thiocyanate extraction into the polymer via formation of strong complex with the ionophore and simultaneous protonation of the indicator dye yielding the optical response at 545nm. The developed optochemical sensor exhibited high selectivity for thiocyanate over other anions including the most lipophilic species such as salicylate and perchlorate. For instance, the optical selectivity coefficients, logKSCN,anionopt, were as follow: ClO4-=-5.8; Sal-=-4.0; NO3-˂-6. Further, the thiocyanate optical selectivity obtained using the present optochemical sensor was greatly enhanced in comparison with that obtained using an anion-exchanger based sensor. Also, the optimized optochemical sensor exhibited micro-molar detection limit with 2min response time at pH4.5 using acetate buffer. The reversibility of the optimized sensor was poor due to strong ligation of the thiocyanate to the central Metal ion, log K=14.1, which can be overcome by soaking the optode in sodium hydroxide followed by soaking in buffer solution. The developed sensor was utilized successfully for the determination of thiocyanate in human saliva and in spiked saliva samples.

Development of ionophore-based nanosphere emulsion incorporating ion-exchanger for complexometric titration of thiocyanate anion

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