New hydrazine sensors based on electropolymerized meso-tetra(4-sulphonatephenyl)porphyrinate manganese(III)/silver nanomaterial.

A new electrocatalytic active porphyrin nanocomposite material was obtained by electropolymerization of meso-tetra(4-sulphonatephenyl)porphyrinate manganese(III) complex (MnTPPS) in alkaline solutions containing sub-micromolar concentrations of silver chloride. The modified glassy carbon electrodes efficiently oxidize hydrazine at 10mV versus Ag/AgCl, dramatically decreasing the overpotential of conventional carbon electrodes. The analytical characteristics of this amperometric sensor coupled with batch injection analysis (BIA) technique were explored. Wide linear dynamic range (2.5x10(-7) to 2.5x10(-4)molL(-1)), good repeatability (R.S.D.=0.84%, n=30) and low detection (3.1x10(-8)molL(-1)) and quantification (1.0x10(-7)molL(-1)) limits, as well as very fast sampling frequency (60 determinations per hour) were achieved.

Fast BIA-amperometric determination of isoniazid in tablets.

This paper proposes a new, fast and precise method to analyze isoniazid based on the electrochemical oxidation of the analyte at a glassy carbon electrode in 0.1M NaOH. The quantification was performed utilizing amperometry associated with batch injection analysis (BIA) technique. Fast sequential analysis (60 determinations h(-1)) in an unusually wide linear dynamic range (from 2.5 x 10(-8) to 1.0 x 10(-3)M), with high sensitivity and low limits of detection (4.1 x 10(-9)M) and quantification (1.4 x 10(-8)M), was achieved. Such characteristics allied to a good repeatability of the current responses (relative standard deviation of 0.79% for 30 measurements), were explored for the specific determination of isoniazid in isoniazid-rifampin tablet.

Determination of salbutamol in syrups by capillary electrophoresis with contactless conductivity detection (CE-C(4)D).

This paper describes the separation and quantification of salbutamol in pharmaceutical products (salbutamol syrups) by capillary electrophoresis (CE) with contactless conductivity detection (C(4)D). The system was studied by micellar electrokinetic capillary chromatography (MEKC) and free solution capillary electrophoresis (FSCE), being the latter chosen in function of best resolution and sensitivity in comparison with the MEKC method. CE-C(4)D was applied to analysis of salbutamol in syrups utilizing 1.0 x 10(-2) molL(-1) acetic acid/sodium acetate buffer (pH 4.9) as running electrolyte. Tetraethylammonium (TEA) solution was used as internal standard. The results obtained include a linear dynamic range from 7. x 10(-5) to 3.0 x 10(-4) molL(-1) and good repeatability (R.S.D.=4.7% for n=10 for a 7.0 x 10(-5) molL(-1) salbutamol solution). The detection limit was calculated as 1.0 x 10(-5) molL(-1) and the limit of quantification was estimated as 3.3 x 10(-5) molL(-1). For syrups analysis the reproducibility presented deviations between 1.5% and 2.5% (three different days) obtained for measurements in triplicate.

Amperometric quantification of sodium metabisulfite in pharmaceutical formulations utilizing tetraruthenated porphyrin film modified electrodes and batch injection analysis.

The performance of a glassy carbon electrode modified with a porphyrin film formed by the [Co(TPyP){Ru(bipy)(2)Cl}(4)](TFMS)(5).H(2)O complex for the analysis of sodium metabisulfite in pharmaceuticals is described. The sensor can be rapidly and easily prepared by drop-casting of a microliter volume of a diluted methanolic solution of the complex onto the electrode surface. The modified electrode with a supramolecular cobalt porphyrin film led to more favorable responses than the bare electrode. This can be ascribed to the much faster electron transfer processes to the analyte mediated by the tetraruthenated porphyrin and to the protection of the electrode against fouling. The association of the amperometric sensor with the batch injection analysis technique led to results that combine good repeatability of the current responses (relative standard deviation of 0.94% for 30 measurements), wide linear dynamic range (2.5x10(-7)molL(-1) to 5.0x10(-4)molL(-1)), high sensitivity and low limits of detection (8.1x10(-8)molL(-1)) and quantification (2.7x10(-7)molL(-1)). The system was successfully applied to sodium metabisulfite quantification in commercial samples of injection formulations of sodium (or potassium) diclofenac. The results compared well with those obtained by the polarographic method.

Cobalt oxide/tetraruthenated cobalt-porphyrin composite for hydrogen peroxide amperometric sensors.

A new composite material constituted by mu-{5,10,15,20-tetra(4-pyridyl)porphyrinato cobalt(iii)}-tetrakis-{chloro-bis-(2,2'-bipyridine)ruthenium(ii)} complex (or CoTRP) and cobalt oxide, exhibiting high stability and sensitivity for the quantification of hydrogen peroxide, was obtained by the electrochemical polymerization of the tetraruthenated cobalt porphyrin in alkaline medium. The optimized experimental conditions for the preparation of the modified glassy carbon electrodes and for analysis of H2O2 were carefully determined. Fast sequential analysis (120 determinations h(-1)) in a wide linear dynamic range (5.0 x 10(-7) mol L(-1) to 2.0 x 10(-3) mol L(-1)), with high sensitivity and low detection limit (2.0 x 10(-7) mol L(-1)), was achieved by using these electrodes and the batch injection analysis (BIA) technique. Such characteristics allied to a good stability were explored for the specific determination of hydrogen peroxide in six commercial cosmetics and pharmaceutical product samples, giving results in excellent agreement with those obtained by the spectrophotometric method.

Bia-amperometric quantification of salbutamol in pharmaceutical products.

This paper presents a simple, rapid and reproducible method of analysis of salbutamol in pharmaceutical products, utilizing batch injection analysis (BIA) associated with amperometric detection. A study of salbutamol oxidation demonstrated a strong dependence between electrode fouling and pH. All determinations were done utilizing a glassy carbon electrode in presence of 3.0moll(-1) NaOH. A large linear dynamic range from 8x10(-7) to 2x10(-4)moll(-1) was obtained by using an injected volume of 100mul with a detection limit of 2.5x10(-7)moll(-1). R.S.D. of 0.92% for 50 successive injections of 4x10(-6)moll(-1) of salbutamol and a sample throughput of 60 samples per hour were achieved. The method was applied for salbutamol quantification in syrups.