New solid-state membrane and coated wire potentiometric sensors for the determination of Zn(II) ions based on nanoparticles.

The first, novel solid-state membrane sensor for Zn(II) determination is developed based on ZnS nanoparticles. ZnS nanoparticles are synthesized by chemical co-precipitation and investigated via X-ray diffraction, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and impedance study. X-ray diffraction shows that the prepared ZnS nanoparticles have an average domain size of 5.72 nm, which is very close to the particle size obtained from TEM observations (6.30 nm). The ZnS nanoparticles are pressed into disks and examined as electroactive solid-state membrane. Solid-state membrane and coated wire sensors are fabricated. They display linear responses over concentration ranges of 1.0 × 10-5 to 1.0 × 10-1 mol L-1 Zn2+ ions with cationic slopes of 28.9±0.2 and 25.9±0.2 mV decade-1 for the solid-state membrane and coated wire sensors, respectively. The lower limits of detection are 2.86 × 10-6 and 4.60 × 10-6 mol L-1 Zn2+ ions for the solid-state membrane and coated wire sensors, respectively. The response time for the two sensors is instantaneous (1 s), and the useful lifetimes for the solid-state membrane and coated wire sensors are long (10 and 6 months, respectively). The solid-state membrane sensor is utilized for the quantification of Zn(II) ions in brass alloys and pharmaceutical preparations.

New potentiometric and spectrophotometric methods for the determination of dextromethorphan in pharmaceutical preparations.

New, simple and convenient potentiometric and spectrophotometric methods are described for the determination of dextromethorphan hydrobromide (DXM) in pharmaceutical preparations. The potentiometric technique is based on developing a potentiometric sensor incorporating the dextromethorphan tetrakis(p-chlorophenyl)borate ion-pair complex as an electroactive species in a plasticized PVC matrix membrane with o-nitophenyl octyl ether or dioctyl phthalate. The sensor shows a rapid near Nernstian response of over 1 × 10(-5) - 1 × 10(-2) mol L(-1) dextromethorphan in the pH range of 3.0 - 9.0. The detection limit is 2 × 10(-6) mol L(-1) DXM and the response time is instantaneous (2 s). The proposed spectrophotometric technique involves the reaction of DXM with eriochrom black T (EBT) to form an ion-associate complex. Solvent extraction is used to improve the selectivity of the method. The optimal extraction and reaction conditions have been studied, and the analytical characteristics of the method have been obtained. Linearity is obeyed in the range of 7.37 - 73.7 × 10(-5) mol L(-1) DXM, and the detection limit of the method is 1.29 × 10(-5) mol L(-1). The relative standard deviation (RSD) and relative error for six replicate measurements of 3.685 × 10(-4) mol L(-1) are 0.672 and 0.855%, respectively. The interference effect of some excepients has also been tested. The drug contents in pharmaceutical preparations were successfully determined by the proposed methods by applying the standard-addition technique.

Iron(II)-phthalocyanine as a novel recognition sensor for selective potentiometric determination of diclofenac and warfarin drugs.

Construction and characterization of potentiometric membrane sensors for quantification of diclofenac and warfarin drugs are described. The membranes of the sensors incorporate 1.8 wt.% iron(II)-phthalocyanine (Pc) as a molecular recognition reagent, 64.3 wt.% dibutylsebacate (DBS) solvent mediator, 1.8 wt.% tridodecylmethylammonium chloride (TDMAC) as membrane additive and 32.1 wt.% poly(vinyl chloride) (PVC) as a matrix. The sensors display linear response for 1 x 10(-2) to 9 x 10(-6) mol l(-1) (detection limit 5.4 x 10(-6) mol l(-1)) and 1 x 10(-2) to 5 x 10(-6) mol l(-1) (detection limit 3 x 10(-6) mol l(-1)) with anionic slopes of -61 +/- 1 and -63 +/- 1 mVdecade(-1) over the pH range 5.5-9 for declofenac and warfarin, respectively. Validation of the assay methods according to the quality assurance standards confirms their suitability for quality control purposes. Use of the sensor for the assay of various formulations of the drugs shows a mean average recovery of 99.7% of the nominal values and a mean precision of +/-0.3%. Significantly improved accuracy, precision, response time, stability, selectivity and sensitivity are offered by these simple and cost-effective potentiometric sensors compared with other standard techniques.

New highly selective picrate sensors based on charge-transfer complexes.

Two novel highly selective potentiometric membrane sensors responsive to picrate ion were developed. They are based on the use of N,N'-dibenzoyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (DD18C6)-picrate and Kryptofix 222-picrate charge-transfer complexes as novel electroactive materials in poly(vinyl chloride) matrix membranes plasticized with o-nitrophenyloctylether or dioctylphthalate. The sensors show a Nernstian response with anionic slopes of -59.0 +/- 0.1 and -58.0 +/- 0.2 mV decade(-1) over concentration ranges of 6.0 x 10(-5) - 1.0 x 10(-2) and 7.0 x 10(-5) - 1.0 x 10(-2) mol l(-1) picrate ion and pH ranges of 5-11.5 and 5.5-11.5 for DD18C6 and Kryptofix 222 based picrate sensors, respectively. Both sensors show highly selectivity towards picrate ion over many hydrophilic and lipophilic anions, and exhibit a non-Hofmeister selectivity sequence, which is an improvement over methods reported so far. The sensors are used for the titrimetric determination of alkaloids using picrate as a titrant.

Novel ibuprofen potentiometric membrane sensors based on tetraphenylporphyrinato indium(III).

Two novel potentiometric membrane sensors responsive to the ibuprofen drug have been developed. These incorporate poly(vinyl chloride) and polyurethane matrix membranes containing 5,10,15,20-tetraphenylporphrinato (TPP) indium(II) ionophore plasticized with dibutylsebacate. The sensors show a near-Nernstian response with anionic slopes of -53 and -55 mV decade(-1), over the concentration range of 4.2 x 10(-6)-1.0 x 10(-2) and 3.3 x 10(-6)-1.0 x 10(-2) M ibuprofen within pH ranges of 4-9 and 5-9 for PVC and PU matrix membranes, respectively. A sensor based on a polyurethane membrane displays a lower detection limit and a wider linear working range, and a sensor based on a PVC membrane exhibits a better overall selectivity, especially in the presence of lipophilic organic anions. Both sensors are used for the quantification and quality-control assessment of ibuprofen in pharmaceutical preparations. The average recoveries are 99.1+/-0.3% and 99.3+/-0.3% for TPP In(III)-PVC and TPP In(III)-PU based membrane sensors, respectively. High selectivities towards ibuprofen in the presence of many anions, drug excipients and diluents are offered by both sensors, which exhibit a non-Hofmeister selectivity pattern.

LC and TLC determination of cinnarizine in pharmaceutical preparations and serum.

New high performance liquid chromatography (HPLC) and thin layer densitometry (TLC) methods are developed for quantification of cinnarizine in dosage forms in the presence of its photo-degradation products and related substances and in the presence of its metabolites in serum. Mobile phases consisting of benzene-methanol-formic acid (80:17:3) and methanol-acetate buffer of pH 4 (70:30) are satisfactorily used for resolution of cinnarizine from associated substances by TLC and HPLC techniques, respectively. The lower detection limits are 16 and 10 ng microl(-1) of cinnarizine with standard deviations of 1.3 and 1.1% with TLC and HPLC, respectively. The methods are used for assessment of drug purity, stability, bioavailability, bioequivalency and tablet dissolution rate. Four cinnarizine related substances and six drug degradation products are isolated and identified by infrared and mass spectrometry. The results obtained by both techniques are in good agreement and offer the advantages of reproducibility and accuracy.