Flow injection analysis of paracetamol using a biomimetic sensor as a sensitive and selective amperometric detector

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

Cobalt phthalocyanine as a biomimetic catalyst in the amperometric quantification of dipyrone using FIA

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

Flow injection amperometric determination of procaine in pharmaceutical formulation using a screen-printed carbon electrode

A rapid and simple method for procaine determination was developed by flow injection analysis (FIA) using a screen-printed carbon electrode (SPCE) as amperometric detector. The present method is based on the amine/hydroxylamine oxidation from procaine monitored at 0.80 V on SPCE in sodium acetate solution pH 6.0. Using the best experimental conditions assigned as: pH 6.0, flow rate of 3.8 mL min(-1), sample volume of 100 mu L and analytical path of 30 cm it is possible to construct a linear calibration curve from 9.0 x 10(-6) to 1.0 x 10(-4) mol L-1. The relative standard deviation for 5.0 x 10(-5) mol L-1 procaine (15 repetitions using the same electrode) is 3.2% and detection limit calculated is 6.0 x 10(-6) mol L-1. Recoveries obtained for procaine gave a mean values from 94.8 to 102.3% and an analytical frequency of 36 injections per hour was achieved. The method was successfully applied for the determination of procaine in pharmaceutical formulation without any pre-treatment, which are in good accordance with the declared values of manufacturer and an official method based on spectrophotometric analysis. (c) 2006 Elsevier B.V. All rights reserved.

Flow injection amperometric detection of ascorbic acid using a Prussian Blue film-modified electrode

The PB film-modified electrode was used as an amperometric detector for flow injection analysis of ascorbic acid. The modified electrode detector showed good sensitivity, stability and reproducibility. The calibration curve for ascorbic acid was linear over the concentration range from 5.0 x 10(-6) to 1.0 x 10(-3) mol l(-1) with a slope of 19.9 mA mol(-1) per litre and a correlation coefficient of 0.999. The detection limit of this method was 2.49 x 10(-6) mol l(-1). The relative standard deviation of six replicate injections of 2.5 x 10(-4) mol l(-1) ascorbic acid was 2.5%. The results obtained for ascorbic acid determination in pharmaceutical products are in good agreement with those obtained by using the procedure involving the reaction between triiodide and ascorbic acid. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Desenvolvimento de detector eletroquímico para cromatografia líquida de alta eficiência baseado em um eletrodo modificado com nanopartículas metálicas para determinação de ácidos carboxílicos em vinhaça de cana-de-açúcar

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

Structural and functional characteristics of selected soft wheat starches

Starches from eight soft wheat samples (two parent lines and six offspring) were isolated; relationships between their structures and properties were examined. Branch chain-length distributions of amylopectins were determined by using high-performance anion exchange chromatography equipped with an amyloglucosidase reactor and a pulsed amperometric detector (HPAEC-ENZ-PAD). Results showed that the average chain length of the eight samples varied at DP 25.6-26.9. Starch samples of lines 02, 60, 63, 95, and 114 consisted of amylopectins with more long chains (DP greater than or equal to 37) and longer average chain length (DP 26.2-26.9) than that of other samples. These starch samples of longer branch chain length displayed higher gelatinization temperatures (55.3-56.5degreesC) than that of other samples (54.4-54.9degreesC) and higher peak viscosity (110-131 RVU) and lower pasting temperature (86.3-87.6degreesC) than others (83-100 RVU and 88.2-88.9degreesC, respectively). The M-w of amylopectins, determined by using high-performance size exclusion chromatography equipped with multiangle laser-light scattering and refractive index detectors (HPSEC-MALLS-RI), were similar for all samples (6.17 x 10(8) to 6.97 x 10(8)). There were no significant differences in amylose and phosphorus contents between samples. These results indicated that physical properties of wheat starch were affected by the branch-chain length of amylopectin.

Behavior of Peruvian carrot (Arracacia xanthorrhiza) and cassava (Manihot esculenta) starches subjected to heat-moisture treatment

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

PURIFICATION AND CHARACTERIZATION OF SOY COTYLEDON -GLUCOSIDASE

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Phytochemical characterization, antimicrobial activity, and antioxidant potential of Equisetum hyemale L. (Equisetaceae) extracts

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Immobilization of uricase in layer-by-layer films used in amperometric biosensors for uric acid

The layer-by-layer technique was exploited to immobilize the enzyme uricase onto indium tin oxide substrates coated with a layer of Prussian Blue. Uricase layers were alternated with either poly(ethylene imine) or poly(diallyidimethylammoniumchloride), and the resulting films were used as amperometric biosensors for uric acid. Biosensors with optimum perfomance had a limit of detection of 0.15 mu A mu mol 1(-1) cm(-2) with a linear response between 0.1 and 0.6 mu M of uric acid, which is sufficient for use in clinical tests. Bioactivity was preserved for weeks, and there was negligible influence from interferents, as detection was carried out at 0.0 V vs saturated calomel electrode.

Development of an amperometric sensor for potassium ions

Hollandite-type manganese oxides are nanofibrous crystals with sub-nanometer open tunnels that provide a unique property for sensing applications. Sensor based on hollandite-type manganese oxide was investigated for amperometric detection of potassium. With an operating potential of +0.63 V versus SCE, potassium ions produce oxidation currents at the sensor, which can be exploited for quantitative determinations. The amperometric signals are linearly proportional to potassium ions concentration in the range 2.7 x 10(-4) to 9.1 x 10(-4) Mol l(-1) with a correlation coefficient of 0.9990. The construction and renewal are simple and inexpensive.

Phytase immobilization on modified electrodes for amperometric biosensing

Phytase (myo-inositol hexaphosphate phosphohydrolase) and phytic acid (myo-inositol hexaphosphate) play an important environmental role, in addition to being a health issue in food industry. Phytic acid is antinutritional due to its ability to chelate metal ions and may also react with proteins decreasing their bioavailability. In this work, we produced biosensors with phytase immobilized in Layer-by-Layer (LbL) films, which could detect phytic acid with a detection limit of 0.19 mmol L-1, which is sufficient to detect phytic acid in seeds of grains and vegetables. The biosensosrs consisted of LbL films containing up to eight bilayers of phytase alternated with poly(allylamine) hydrochloride (PAH) deposited onto an indium-tin oxide (ITO) substrate modified with Prussian Blue. Amperometric detection was conducted in an acetate buffer solution (at pH 5.5) at room temperature, with the biosensor response attributed to the formation of phosphate ions. In subsidiary experiments with the currents measured at 0.0 V (vs. SCE), we demonstrated the absence of effects from some interferents, pointing to a good selectivity of the biosensor. (c) 2007 Elsevier B.V. All rights reserved.

Electrochemical evaluation of the a carbon-paste electrode modified with spinel manganese(IV) oxide under flow conditions for amperometric determination of lithium

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

Investigation of the interaction between Tc85-11 protein and antibody anti-T cruzi by AFM and amperometric measurements

This present work reports on development of an amperometric immunosensor for the diagnosis of Chagas' disease using a specific glycoprotein of the trypomastigote surface, which belongs to the Tc85-11 protein family of Trypanosoma cruzi (T cruzi). An atomically flat gold surface on a silicon substrate and gold screen-printed electrodes were functionalized with cystatrine and later activated with glutaraldehyde (GA), which was used to form covalent bonds with the purified recombinant antigen (Tc85-11). The antigen reacts with the antibody from the serum, and the affinity reaction was monitored directly using atomic force microscopy or amperometry through a secondary antibody tagged to peroxidase (HRP). Surface imaging allowed to us to differentiate the modification steps and antigen-antibody interaction allowed to distinguish the affinity reactions. In the amperometric immunosensor, peroxidase catalyses the L-2 formation in the presence of hydrogen peroxide and potassium iodide, and the reduction current intensity was measured at a given potential with screen-printed electrodes. The immunosensor was applied to sera of chagasic patients and patients having different systemic diseases. (c) 2006 Elsevier Ltd. All rights reserved.

Digital radiography using digital detector arrays fulfills critical applications for offshore pipelines

Digital radiography in the inspection of welded pipes to be installed under deep water offshore gas and oil pipelines, like a presalt in Brazil, in the paper has been investigated. The aim is to use digital radiography for nondestructive testing of welds as it is already in use in the medical, aerospace, security, automotive, and petrochemical sectors. Among the current options, the DDA (Digital Detector Array) is considered as one of the best solutions to replace industrial films, as well as to increase the sensitivity to reduce the inspection cycle time. This paper shows the results of this new technique, comparing it to radiography with industrial films systems. In this paper, 20 test specimens of longitudinal welded pipe joints, specially prepared with artificial defects like cracks, lack of fusion, lack of penetration, and porosities and slag inclusions with varying dimensions and in 06 different base metal wall thicknesses, were tested and a comparison of the techniques was made. These experiments verified the purposed rules for parameter definitions and selections to control the required digital radiographic image quality as described in the draft international standard ISO/DIS 10893-7. This draft is first standard establishing the parameters for digital radiography on weld seam of welded steel pipes for pressure purposes to be used on gas and oil pipelines.