Mohsen M. Zareh

Effect of presence of 18-crown-6 on the response of 1-pyrrolidine dicarbodithioate-based lead selective electrode.

The lipophilic ammonium salt of 1-pyrrolidine dicarbodithioic acid (PCDT)[I] was introduced as a selective ionophore for a sensitive Pb-ion selective electrode. Also, the effect of immobilization of 18-crown-6 (CW), into the above membrane, on the electrode performance was discussed. The slope of the PCDT-based [I] electrode was (26-30 mV decade(-1)), while it was (29-30 mV decade(-1)) for (PCDT+CW)-based [II] electrode according to the doping time. The linear concentration ranges were (1x10(-6)-1x10(-1) M) and (5x10(-5)-1x10(-1) M) for electrode types [I] and [II] after one-day doping. The working pH ranges were (5.0-10.0) and (7.0-10.0) for electrode types [I] and [II], respectively. Most of the common cations were tested for the evaluation of the electrode selectivity with correlation to the ionic radii of the tested cations. Among them only Na(+), Ag(+) and Fe(3+) were the real interference. Application of using the electrode for the determination of lead in lubrication oil samples was performed with RSD (0.86-1.03%). The obtained results were compared to those of an atomic absorption spectrophotometric method.

Acetylacetone-formaldehyde reagent for the spectrophotometric determination of some sulfa drugs in pure and dosage forms

A new simple and sensitive spectrophotometric procedure for the determination of sulfacetamide sodium (I), sulfadiazine (II), sulfadimidine (III) and sulfathiazole (IV) is based on the reaction of the drug with acetylacetone-formaldehyde reagent to give a yellow product having λmax at 400 nm. Optimization of the reaction conditions has been investigated. A linear correlation was obtained between absorbance at λmax and the concentration. The Beers law limits of I, II, III and IV are 4–80, 4–72, 4–60 and 4–80 μg/ml, respectively. For more accurate results, Ringbom optimum concentration ranges were evaluated to be 6–76, 8–66, 6–56 and 8–75 μg/ml for I, II, III and IV, respectively. The molar absorptivities and Sandell sensitivities for all sulfa drugs under consideration were evaluated. Relative standard deviations of 0.98, 1.07, 0.86 and 0.79% were obtained for I, II, III and IV, respectively. The method has been compared to the official method and found to be simple, accurate (t-test) and reproducible (F-test). The developed procedures were applied for bulk sulfa drugs and some of their dosage forms without interferences from additive and common prescribed drugs.

New ion-selective electrodes for determination of bupivacaine and oxybuprocaine

Abstract PVC membrane electrodes selective for hydrochlorides of the anaesthetics bupivacaine (BpC) and oxybuprocaine (ObC) are prepared. The electrodes have a near Nernstian slope (58 mV for BpC and 51 mV for ObC electrodes) over the range of 1.6 × 10−5-10−1M and 1.3 × 10−1M for BpC and ObC electrodes, respectively. The change in pH of the test solution within the ranges 2.5–6.0 and 3.0–7.4 does not affect the EpC-and ObC-electrodes, respectively. The electrodes have very long life times (10 days for BpC, and 3 months for ObC) and exhibit good seletivity for the investigated compounds with respect to a large number of inorganic cations and organic substances of biological importance. The isothermal coefficients of the electrodes are calculated from the standard electrode potentials at different temperatures. BpC and ObC are determined successfully in some pharmaceutical preparations using the calibration graph technique and potentiometric titration.

Plastic membrane and coated Wire Ion Selective Electrodes for Propylhexedrine

Abstract Propylhexedrine (PX) ion selective electrode based on plasti-cized (PX)-tetraphenylboron with dioctylphthalate in poly(vinyl chloride) (PVC)-matrix. The electrode shows near Nernstian response over the concentration range 2.5×10−5 -10−1 solutions of the drug. The working pH-range of the electrode is 2.5-9.5 at 25°C. The electrode response can be considered Nernstian over the temperature range 25-60°C with isothermal temperature coefficient 0.00025 V/°C. The selectivity coefficient of the electrode is calculated towards several inorganic cations, sugars, amines, amino acids and some other pharmaceutical preparations. Also, a coated wire ion-selective electrode based on the same ion pair was found to give a Nernstian response for a concentration range of 10−4-10−2 M PXH+ solution.

Potentiometric Sensor for Phenylephrine Based on Phenylephrine-tetraphenylborate Lipophilic Salt

Phenylephrine (PE) ion-selective electrode based on incorporation of phenylephrine-tetraphenylborate lipophilic salt in plasticized PVC matrices is constructed. The electrode shows near Nernstian response over the concentration range 1.5 × 10−4-10−1M in solutions of pH 2.9–8.0 at 25°C. The electrode resists the effect of heat in the temperature range 25–55°C exhibiting an isothermal temperature coefficient of 0.0007 V/°C. The selectivity of the electrode for PE towards large number of inorganic cations, sugars and amino acids is investigated. Determination of PE in an eye-drops pharmaceutical preparation is carried out using the proposed electrode as potentiometric sensor.

PVC-MEMBRANES SENSITIVE TO CHLORPHENOXAMINE BASED ON TETRAPHENYLBORATE SALT AND NEUTRAL CARRIER ADDITIVES

ABSTRACT The performance of a chlorphenoxamine membrane based on TpClPB (I) was observed after addition of either dibenzo-18-crown-6 (II), 18-crown-6 (III) or thiophosphates of calix-[6]-derivatives (IV). The Nernstian response changed from 48.4 mV/decade for membrane (I) to 54.7, 54.7 and 53.6 mV/decade for membranes containing neutral carriers (II, III and IV) in addition to the TpClPB. Also, a significant improvement was observed for the selectivity coefficient values for monovalent cations whenever the membranes containing neutral carriers (II, III or IV) were used. The lower limit of the linear range was improved a little by immobilization of the neutral carrier with TpClPB [from 10−4 (type-I) to 5 × 10−5 (types-II, III and IV). The temperature coefficient values are 1.7 × 10−4, 2.0 × 10−4, 4.1 × 10−4 and 2.5 × 10−4 V/°C for electrodes I, II, III and IV, respectively. The determination of chlorphenoxamine HCl in its tablets was applied in the presence of caffeine with a recovery value of 96.9% and RSD = 2.726%.

Effect of using mixed ion-pairs on PVC-membrane electrodes for ephedrine

Mixed ion-pairs based on the use of ephedrinium (EPH)-TPB plus EPH-reineckate (II) and phenylephrine-TPB plus EPH-reineckate (III) were tried for use in plastic membranes. The results were compared to those of an EPH-reineckate (I) single ion-pair electrode. The Nernstian slopes were 50, 49 and 55 mV decade−1 for membranes I, II and III, respectively. The linear concentration ranges were 10−5−10−1, 4.0 × 10−5−10−1 and 6.3 ×−5−10−1M ephedrine. The detection limits were 4 ×−6,10−5 and 1.2 × 10−5M ephedrine for membranes I, II and III, respectively. The pH ranges were 4−9, 3−9 and 2−8 for I, II and III-membranes, respectively. Selectivity coefficient values for membrane II were better than those for membranes I and III. The effects of increasing KC1 concentration and temperature changes were explained for the three electrodes. The isothermal temperature coefficients were 0.00145, 0.0007 and 0.00055 V/ °C for electrodes I, II and III. Electrode III was applied for the determination of ephedrine in its pharmeaceutical preparations with an overall relative standard deviation range of 1.3–2.4% and an overall mean recovery value of 98.1%.

Fabrication of an ion-selective electrode for determination of propylhexedrine

Electrodes of both conventional and micro-sizes were based on the use of propylhexedrine-reineckate as the ion-exchanger in a plastic membrane. The electrodes exhibited Nernstian response towards propylhexedrine (PX) over the concentration range 10−6–10−2M and had life spans of up to 2 days continuous work. The working pH range was 2.3–8. Investigation of diverseions reveals good selectivity for propylhexedrine over several inorganic cations, amines, aminoacids, sugars and some pharmaceutical compounds. The electrode was applied for determination of the drug in urine with 99.1% recovery and 0.15–0.31% relative standard deviation.