Potentiometric Sensor for Furosemide Determination in Pharmaceuticals, Urine, Blood Serum and Bovine Milk

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Potentiometric sensor for sorbic acid determination in food products

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Development of a potentiometric sensor for the determination of saccharin in instant tea powders, diet soft drinks and strawberry dietetic jam

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Development of a potentiometric flufenamate ISE and its application to pharmaceutical and clinical analyses

The characteristics, performance, and application of an electrode, namely, Pt vertical bar Hg vertical bar Hg-2(FF)(2)vertical bar Graphite, where FF stands for flufenamate ion, are described. This electrode responds to FF with sensitivity of (-58.6 +/- 1.2) mV decade(-1) over the range 1.0 x 10(-6) - 1.0 x 10(-2) mol L-1 at pH 6.0-9.0 and a detection limit of 7.1 x 10(-7) mol L-1. The electrode is easily constructed at a relatively low cost with fast response time (within 10-25 s) and can be used for a period of 5 months without any considerable change in its performance characteristics. The proposed electrode displayed good selectivity for flufenamate in the presence of several substances as well as in the presence of some carboxylate and inorganic anions. The electrode was successfully applied to the determination of flufenamic acid in pharmaceuticals and human serum samples.

A pH optode based on thymol blue: application to determination of CO2 using flow injection analysis system

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Adsorptive potentiometric stripping analysis of nucleic acids at mercury electrodes

The application of adsorptive stripping potentiometry to the reductive detection of nucleic acids at mercury electrodes is reported. Compared to analogous voltammetric stripping modes, constant current potentiometric stripping analysis (PSA) effectively addresses the hydrogen discharge background problem, and hence greatly improves the characteristics of the superimposed cytosine/adenine (CA) reduction peak. Compared to earlier schemes for trace measurements of nucleic acids at mercury or carbon electrodes that rely on anodic signals arising from the guanine residue, convenient quantitation can now be carried out in connection with the cytosine and adenine residues. Variables influencing the adsorptive PSA response are explored and optimized. With five minute accumulation, the detection limits for tRNA, ssDNA and dsDNA are 30 mu g l(-1), 60 mu g l(-1) and 2 mg l(-1), respectively. Such different values reflect the strong dependence of the PSA CA signal upon the nucleic-acid structure. This allows the quantitation of ssDNA or tRNA in the presence of dsDNA, and offers new possibilities for electrochemical studies of DNA structure and interactions.

Determination of solubility product of mercurous acetate at various ionic strengths in aqueous medium

The conditionals (K-ps) and thermodynamics (K-ps(o)) solubility products of mercurous acetate have been determined, in aqueous solution, at 25 degrees C and ionic strength (I) comprised between 0.300 and 3.000 mol/L (NaClO4). The investigation was carried out potentiometrically by using a second class electrodes which responds to acetate ions. The values obtained for [pK(ps) (I)] were: 9.49+/-0.08 (0.000); 9.51+/-0.08 (0.300); 9.53+/-0.08 (0.500); 9.54+/-0.08 (0.700); 9.55+/-0.09 (0.900), 9.57+/-0.09 (1.200); 9.59+/-0.10(1.500); 9.61+/-0.10 (1.800); 9.63+/-0.10 (2.100); 9.65+/-0.11 (2.400); 9.67+/-0.11 (2.700) e 9.69+/-0.12 (3.000).

A new potentiometric ibuprofenate ion sensor immobilized in a graphite matrix for determination of ibuprofen in tablets

The characteristics, performance, and application of an electrode, namely, Pt vertical bar Hg vertical bar Hg-2(IBP)(2)vertical bar Graphite, where IBP stands for ibuprofenate ion, are described. This electrode responds to IBP with sensitivity of (58.6 +/- 0.9) mV decade 1 over the range 5.0 x 10(-5)-1.0 x 10(-1) mol L-1 at pH 6.0-9.0 and a detection limit of 3.8 x 10(-5) mol L-1. The electrode is easily constructed at a relatively low cost with fast response time (within 1530 s) and can be used for a period of 5 months without any considerable divergence in potentials. The proposed sensor displayed good selectivity for ibuprofen in the presence of several substances, especially concerning carboxylate and inorganic anions. It was used for the direct assay of ibuprofen in commercial tablets by means of the standard additions method. The analytical results obtained by using this electrode are in good agreement with those given by the United States Pharmacopeia procedure. (c) 2006 Elsevier B.V. All rights reserved.

Benzoate ion determination in beverages by using a potentiometric sensor immobilized in a graphite matrix

The characteristics, performance, and application of an electrode, namely. Pt\Hg\Hg-2(Bzt)(2)\graphite, where Bzt stands for benzoate ion. are described. This electrode responds to Bzt with sensitivity of 57.7 +/- 1.0 mV/decade over the range 5 x 10(-4)-1 x 10(-1) mol l(-1) at pH 6.0-8.0 with a detection limit of 1.6 x 10(-4) mol l(-1). The electrode shows easy construction, fast response rime (between 10-30 s), low-cost, acid excellent response stability (lifetime > 6 months, in continuous use), the proposed sensor displayed good selectivity for benzoate in the presence of several carboxylate and inorganic anions. It was used to determine benzoate in various beverages by means of the standard additions method. The results obtained by using this electrode compared very favorably with those given by the official AOAC spectrophotometric method and by a HPLC procedure as well. (C) 2001 Elsevier B.V. B.V. All rights reserved.

p-Aminobenzoate ion determination in pharmaceutical formulations by using a potentiometric sensor immobilized in a graphite matrix

The characteristics, performance, and application of an electrode, namely, Pt\Hg\Hg-2(PABzt)(2)\ graphite, where PABzt stands for p-aminobenzoate ion, are described. This electrode responds to PABzt with sensivity of (58.1 +/- 1.0) mV per decade over the range 1.0 x 10(-4) to 1.0 x 10(-1) mol l(-1) at pH 6.5-8.0 and a detection limit of 3.2 x 10(-5) mol l(-1). The electrode shows easy construction, fast response time (within 10-30 s), low-cost, and excellent response stability (lifetime greater than 6 months, in continuous use). The proposed sensor displayed good selectivity for p-aminobenzoate in the presence of several substances, especially, concerning carboxylate and inorganic anions. It was used to determine p-aminobenzoate in pharmaceutical formulations by means of the standard additions method. The results obtained by using this electrode compared very favorably with those given by an HPLC procedure. (C) 2004 Elsevier B.V. All rights reserved.

Development of a potentiometric mefenamate ion sensor for the determination of mefenamic acid in pharmaceuticals and human blood serum

The characteristics, performance, and application of a novel and simple electrode, namely Pt vertical bar Hg vertical bar Hg-2(MF)(2)vertical bar Graphite, where MF stands for mefenamate ion, are described. This electrode responds to MF with sensitivity of (58.9 +/- 0.7) mV decade(-1) over the range 1.0 x 10(-6) to 1.0 x 10(-2) mol L-1 at pH 6.0-9.0 and a detection limit of 6.2 x 10(-7) mol L-1. The electrode is easily constructed at a relatively low cost with fast response time (within 10-25 s) and can be used for a period of 4 months without significant change in its performance characteristics. The proposed sensor displayed good selectivity for mefenamate in the presence of several substances, especially concerning carboxylate and inorganic anions. The potentiometric sensor was successfully applied to the determination of mefenamic acid in pharmaceuticals and human serum samples. (c) 2007 Elsevier B.V. All rights reserved.

Determination of diclofenac in pharmaceutical preparations using a potentiometric sensor immobilized in a graphite matrix

The characteristics, performance, and application of an electrode, namely Pt| Hg|Hg-2(DCF)(2)|graphite, where DCF stands for diclofenac ion, are described. This electrode responds to diclofenac with sensitivity of (58.1 +/- 0.8) mV/decade over the range 5.0 x 10(-5) to 1.0 x 10(-2) Mol l(-1) at pH 6.5-9.0 and a detection limit of 3.2 x 10(-5) mol l(-1). The electrode is easily constructed at a relatively low cost with fast response time (within 10-30 s) and can be used for a period of 5 months without any considerable divergence in potentials. The proposed sensor displayed good selectivity for diclofenac in the presence of several substances, especially concerning carboxylate and inorganic anions. It was used to determine diclofenac in pharmaceutical preparations by means of the standard additions method. The analytical results obtained by using this electrode are in good agreement with those given by the United States Pharmacopeia procedures. (c) 2005 Elsevier B.V. All rights reserved.

Tangential-flow ultrafiltration: a versatile methodology for determination of complexation parameters in refractory organic matter from Brazilian water and soil samples

In this work the copper(II) complexation parameters of aquatic organic matter, aquatic and soil humic substances from Brazilian were determined using a new versatile approach based on a single-stage tangential-flow ultrafiltration (TF-UF) technique (cut-off 1 kDa) and sensitive atomic spectrometry methods. The results regarding the copper(II) complexation capacity and conditional stability constants obtained for humic materials were compared with those obtained using direct potentiometry with a copper-ion-selective electrode. The analytical procedure based on ultrafiltration is a good alternative to determine the complexation parameters in natural organic material from aquatic and soil systems. This approach presents additional advantages such as better sensibility, applicability for multi-element capability, and its possible to be used under natural conditions when compared with the traditional ion-selective electrode.

Reduction of mercury(II) by tropical river humic substances (Rio Negro) - Part II. Influence of structural features (molecular size, aromaticity, phenolic groups, organically bound sulfur)

The influence of structural features of tropical river humic substances (HS) on their capability to reduce mercury(II) in aqueous solutions was studied. The HS investigated were conventionally isolated from Rio Negro water-Amazonas State/Brazil by means of the collector XAD 8. In addition, the isolated HS were on-line fractionated by tangential-flow multistage ultrafiltration (nominal molecular-weight cut-offs: 100, 50, 30, 10, 5 kDa) and characterized by potentiometry and UV/VIS spectroscopy. The reduction of Hg(II) ions to elemental Hg by size-fractions of Rio Negro HS was assessed by cold-vapor AAS (CVAAS). UV/VIS spectrometry revealed that the fractions of high molecular-size (F-1 > 100 kDa and F-2: 50-100 kDa) have a higher aromaticity compared to the fractions of small molecular-size (F-5: 5-10 kDa, F-6: < 5 kDa). In contrast, the potentiometric study showed different concentration of functional groups in the studied HS fractions. The reduction of Hg(II) by aquatic HS fractions at pH 5 proceeded in two steps (I, II) of slow first order kinetics (t(1/2) of I: 160 min, t(1/2) of II: 300 min) weakly influenced by the molecular-size, in contrast to the differing degree of Hg(II) reduction (F-5 > F-2 > > F-1 > F-3 > F-4 > > F-6). Accordingly, Hg(II) ions were preferably reduced by HS molecules having a relatively high ratio of phenolic/carboxylic groups and a small concentration of sulfur. From these results a complex 'competition' between reduction and complexation of mercury(II) by aquatic HS occurring in tropical rivers such as the Rio Negro can be suggested. (C) 2003 Elsevier B.V. All rights reserved.

Estudio de la pasivacion de la aleacion Co-Cr-Mo en suero fisiologico

Results are presented on the mechanism of passivation of Co-Cr-Mo biological implant alloys in physiological serum using open circuit potentiometry, potentiodynamic curves, and electrochemical impedance spectroscopy. The potential dependence of impedance data and the analysis of the parameters obtained indicate a progressive diminution of the initial layer thickness and the simultaneous formation of a second higher resistive layer. In more severe conditions than the existent in human body, the metallographic examination of the alloy surface shows localized corrosion in interdendritric regions. Elemental analysis of the surface reveals the presence of higher chromium content in these regions. The presence of chlorine was not detected, which suggested that during preferential attack, soluble species are also formed.