Abdelaziz Bouklouze

Use of ethylene-vinyl-acetate as a new membrane matrix for calcium ion-selective electrode preparation

A new polymer matrix based membrane electrode with an ion-exchanger responding to calcium was constructed by dissolving the copolymer ethylene-vinyl-acetate together with the ion-exchanger in chloroform in the presence of a mixture of dioctylphthalate-nitrobenzene as plasticizer. The ion-exchanger used as the electroactive component was calcium didecyl phosphate in di-(n-octylphenyl) phosphonate (Orion). This electrode exhibited near-Nernstian response over the concentration range 10(-1)-4 x 10(-6)M calcium. The pH did not affect the electrode performance within the range 8-11. Response time varied from 15 to 120 sec and the lifetime exceeded six months. The membrane is subject to static charge buildup, but this is avoided by controlling the level of dryness of the membrane. Selectivity coefficients determined for both monovalent and divalent cations showed negligible interference by most of these ions. The electrode was applied successfully to the determination of calcium in commercial mineral waters.

Comparative study of three polymeric membrane electrodes selective to tizanidine

Abstract Three types of polymeric electrodes were using a poly(vinyl chloride) film plasticized with a dioctyl phthalate-nitrobenzene mixture and containing an ion pair of the drug tizanidine. The membrane of the so-called conventional electrode, which includes an internal Ag/AgCl reference, was immobilized on a micropipette tip. A single-layer electrode was prepared by coating a graphite rod with the membrane, while the graphite rod of a two-layer electrode was previously coated with a poly(4,4′-biphenol) film before the sensitive membrane was deposited. These electrodes exhibit a Nernstian response in the concentration range 5 x 10 −6 −1 x 10 −2 M with a slope between 55 and 57 mV per decade. The response is not affected by pH between 3 and 7. The influence of several parameters involved in the construction of these electrodes on their lifetime is discussed, the highest durability being observed for the conventional electrode. Selectivity coefficients against various organic and inorganic cations were evaluated. The conventional electrode was applied to the determination of tizanidine in drug formulations using direct potentiometry.

New modified polymeric electrodes selective to local anaesthetic compounds

New polymeric electrodes responding to the cationic forms of tetracaine (TC), lidocaine (LD), and procaine (PC) were constructed by incorporating their ion-pair complexes (the salts of TC, LD and PC with phosphotungstic acid) into ethylene-vinyl acetate (E/VAC) copolymer. Other ion pairing agents investigated were silicotungstate and tetraphenylborate. The phosphotungstic acid resulted in the best linear and Nernstian response. A 1:1 (v/v) mixture of dioctyl phthalate (DOP) and nitrobenzene (NB) was used as plasticizer. The electrodes exhibited linear response over the concentration ranges 10(-2)-5.6 x 10(-6), 10(-2)-2.5 x 10(-5) and 10(-2)-1.8 x 10(-5) M of TC, LD and PC, respectively. pH did not affect the electrode performances within the ranges 2.7-6.3, 2.6-6.7 and 2.8-7.5 for the three electrodes, respectively. Interferences are negligible for many organic base and alkali metal cations. Cations of similar structure interfere with LD and PC, but not appreciably with TC. Direct potentiometry was used to determine these compounds in pharmaceutical preparations with accurate results.

Potentiometric sensor for hydroxyzine determination

A new polymeric membrane electrode has been developed for the determination of hydroxyzine. The electrode was constructed by solubilizing the hydroxyzine silicotungstate ion pair into a polyvinylchloride matrix plasticized by nitrophenyloctylether. The electrode exhibited a near-Nernstian response (57u2005mV/decade) in the concentration range comprised between 1×10−2u2005M and 6×10−7u2005M with a lower limit of detection of 2.5×10−7u2005M. The electrode response was not sensitive to pH changes between 2.8 and 6.9 and not affected by possible interfering species such as cetirizine and pharmaceutical excipients. The electrode was successfully applied to the determination of hydroxyzine in pharmaceuticals and in a dissolution profile study of tablets. The results were validated by comparison with LC and spectrophotometric assays according to the USP Pharmacopoeia methods.

Barium ion-selective electrode based on a new neutral carrier complex

Abstract Three derivatives of a new class of ionophores belonging to the binaphthyl polyethers and exhibiting high lipophilicity were synthesized and evaluated as neutral carriers for the fabrication of a barium ion-selective electrode. The influence of the length of the ether side-chain and of the substitution of the amido group ending this side-chain on the complexing capability of barium ion is discussed. The ion-selective membrane was constructed by incorporating the selected ionophore in an ethylene-vinyl acetate copolymer which was previously dissolved in tetrahydrofuran. Nitrophenyl octyl ether was used as a plasticizer and a small amount of sodium tetraphenylborate was added as a lipophilic anion. The influence of the nature of the plasticizer and of the amount of incorporated ionophore on the characteristics of the electrode is discussed. The response of this electrode is linear in the range 0.1–3 × 10 −6 M with a slope of 30 mV per decade. The potential is not affected by pH modifications in the range 1.6–8. 1. Selectivity coefficients determined for both monovalent and divalent cations show negligible interference from most of them. The electrode exhibits excellent potential stability and an operational lifetime of more than 5 months. Moreover, this electrode is not poisoned by copper(II) ions, in contrast with an ion-exchanger liquid membrane electrode, which exhibits a potential shift, or with a PVC membrane electrode, which requires in this instance a long recovery time. This electrode was applied successfully to the determination of sulphate ions in commercial mineral waters using potentiometric titration.

Determination of Fluoride in Tap Water in Morocco using a Direct Electrochemical Method

This study aimed to analyze the fluoride concentration in tap drinking water in different cities of Morocco using an electrochemical ion-selective method. Three samples were collected from each thirteen selected cities in the period between March and May 2011. The median value of fluoride was 0.94xa0mg/L (0.21–2.97). High fluoride concentrations (>0.8xa0mg/L) were found in sixteen cities. Very high values were found in phosphate regions such as Khouribga which is known to be an endemic dental fluorosis area. This study has shown that the concentration of fluoride in drinking water exceeds the limit especially in phosphate regions.

Selected-ion flow-tube mass-spectrometry (SIFT-MS) fingerprinting versus chemical profiling for geographic traceability of Moroccan Argan oils

This study investigated the effectiveness of SIFT-MS versus chemical profiling, both coupled to multivariate data analysis, to classify 95 Extra Virgin Argan Oils (EVAO), originating from five Moroccan Argan forest locations. The full scan option of SIFT-MS, is suitable to indicate the geographic origin of EVAO based on the fingerprints obtained using the three chemical ionization precursors (H3O+, NO+ and O2+). The chemical profiling (including acidity, peroxide value, spectrophotometric indices, fatty acids, tocopherols- and sterols composition) was also used for classification. Partial least squares discriminant analysis (PLS-DA), soft independent modeling of class analogy (SIMCA), K-nearest neighbors (KNN), and support vector machines (SVM), were compared. The SIFT-MS data were therefore fed to variable-selection methods to find potential biomarkers for classification. The classification models based either on chemical profiling or SIFT-MS data were able to classify the samples with high accuracy. SIFT-MS was found to be advantageous for rapid geographic classification.

Bisphénol A : à nouveau risque, nouveau défi !

Le bisphenol A est un compose chimique issu de la reaction entre le phenol et l’acetone. C’est un monomere chimique utilise dans la production du polycarbonate et des resines epoxy-phenoliques lesquels sont utilises dans plusieurs domaines (alimentation, dentisterie, papeterie, dispositifs medicaux, etc.). La principale source d’exposition de la population generale au bisphenol A serait alimentaire par passage dans l’aliment ou la boisson a partir des polymeres en plastiques et resines epoxy, utilises pour les emballer. Le bisphenol A est un perturbateur endocrinien avec une activite œstrogenique. Il entraine une diminution de la production du sperme, augmente le volume de la prostate et altere le developpement de la morphologie vaginale et du cycle œstrogenique ; d’autres etudes ont suggere l’effet sur la thyroide, la prostate, le systeme cardiovasculaire, il pourrait induire le diabete de type 2, ainsi que des anomalies enzymatiques du foie. Les effets sur la sante sont connus actuellement a la suite d’etudes chez l’animal. Cependant, les etudes chez l’homme ne sont pas plausibles et ne confirment pas les effets decrits sur la sante ce qui necessite d’autres etudes plus poussees.

Développement et validation d’une méthode de dosage de la paraphénylène diamine par chromatographie gazeuse couplée à la spectrométrie de masse

Paraphenylenediamine is an aromatic amine used as a hair dye; it is responsible for poisoning characterized by respiratory distress involving life-threatening. The objective of this work is the development and validation of an assay of para-phenylenediamine in the whole blood. The method is based on the determination of paraphenylene diamine in whole blood by gas chromatography-mass spectrometry after liquid-liquid extraction and derivatization. The validation protocol has included the study of the recovery factor of extraction, the measurement range, accurency, repetability and intermediate precision. The calibration curve was linear between 98 and 1350 μg/L (r = 0.999), the limit of detection and quantification were 37 μg/L and 63 μg/L respectively. The accuracy were 94.7%. Coefficients of variation were (2.3/6.8/9.7%) for repeatability and (4.4/8.7/9.8%) for intermediate precision. The method is suitable for quantification of PPD in acute poisoning situations. A method for the determination of the paraphenylene diamine in the whole blood by gas chromatography coupled to mass spectrometry was developed. The validation of the method showed good linearity, good accuracy and low limit of quantification.