Preparation, Characterization and Study of the Dissociation of Naproxen from Its Chitosan Salt.

Salts of naproxen (NAP) with chitosan (CTS) and reticulated chitosan (CEP) were prepared under optimized conditions to maximize the yield of reaction. The objective was to evaluate the dissociation in water, which can guide studies of release of the drug from biopolymeric salts in pharmaceutical applications. Higher salification was found after 24 h of reaction at 60 °C in a molar ratio 1:1.

Pen sensor made with silver nanoparticles decorating graphite-polyurethane electrodes to detect bisphenol-A in tap and river water samples.

Rapid, on-site detection of emerging pollutants is critical for monitoring health threats and the environment, especially if performed through autonomous systems. In this paper, we report on a new design of a complete electrochemical system whose working (WE), auxiliary (AE) and reference (RE) electrodes were obtained on a pen (PEN Sensor) made with graphite:polyurethane (GPUE). Working electrodes were decorated with spherical, ca.

Thermal behavior of food preservative sorbic acid and its derivates.

Sorbic acid and its potassium and calcium salts used as food preservatives and sorbic chloride were submitted to thermal analysis in order to characterize their thermal behavior on heating and cooling processes, using TG/DTG/DTA, TG-MS, DSC, hot stage microscopy and DRX analysis. Sorbic acid melted and decomposed under dynamic heating. Under isothermal it sublimated without decomposition before melting (T < 134 °C).

Screen-printed disposable electrodes using graphite-polyurethane composites modified with magnetite and chitosan-coated magnetite nanoparticles for voltammetric epinephrine sensing: a comparative study.

Disposable screen-printed electrodes based on the use of graphite-polyurethane composites modified with magnetite nanoparticles (MNP-SPE) or chitosan-coated magnetite nanoparticles (CHMNP-SPE) are described. The MNP and CHMNP were synthetized and comparatively characterized by TEM, XRD, FTIR, and TGA/DTG. The MNP-SPE and CHMNP-SPE were characterized by SEM and EDX.

New series of metal complexes by amphiphilic biopolymeric Schiff bases from modified chitosans: Preparation, characterization and effect of molecular weight on its biological applications.

To improve biological activity of chitosans, new Zn(II), Pd(II) and Pt(II) complexes with biopolymeric amphiphilic Schiff bases anchored in different molecular weight chitosans matrices modified with salicylaldehyde and glycidol were prepared. Salicylaldehyde was introduced to generate complexing Schiff base sites in the chitosans matrix while glycidol is intended to increase the water solubility of the resulting biopolymeric complexes. These novel complexes were characterized using various techniques and assayed for antimicrobial and antitumor activity.

Developing a screen-printed graphite-polyurethane composite electrode modified with gold nanoparticles for the voltammetric determination of dopamine.

A screen-printed electrode (SPGPUE) was prepared with graphite-polyurethane composite ink containing gold nanoparticles (AuNPs), resulting in a screen-printed graphite-polyurethane composite electrode modified with gold nanoparticles (SPGPUE-AuNPs). Gold nanoparticles were prepared by the citrate method and extracted from the water medium since polyurethane is not compatible with humidity. After extraction to chloroform, they were characterized transmission electron microscopy (TEM).

A new look towards the thermal decomposition of chitins and chitosans with different degrees of deacetylation by coupled TG-FTIR.

Chitins and Chitosans with different degrees of deacetylation (DD¯) were analyzed for the first time by thermogravimetry coupled to infrared spectroscopy TG-FTIR in order to evaluate the effect of DD¯ on the thermal decomposition process. DD¯ values of chitins and chitosans were determined by H-NMR and structural difference were investigated by FTIR, SEM and XRD. Thermal stability of chitosan with 98, 87, 71% DD¯, chitins with 47 and 27% DD¯ and commercial α-chitin were evaluated.

Characterization, solubility and biological activity of amphihilic biopolymeric Schiff bases synthesized using chitosans.

Chitosans are versatile biopolymers recognized for their wide range of biological activities. However, the low solubility in neutral and basic solutions restricts the applications. Thus amphiphilic biopolymeric Schiff bases from chitosans, salicylaldehyde and glycidol were successfully synthesized and characterized using H-NMR, UV/Vis, FTIR, TG/DTG-DTA and tested for their antimicrobial activities against plant pathogenic microorganisms and human breast cancer cells (MCF-7).

Simultaneous determination of environmental contaminants using a graphite oxide - Polyurethane composite electrode modified with cyclodextrin.

A composite electrode based on graphite oxide (GrO)-polyurethane (PU) modified with β-cyclodextrin (CD) was proposed for the simultaneous determination of three drugs: terbutaline (TER), nimesulide (NIM), and methocarbamol (MET), as possible contaminants in river water samples. To evaluate the performance of the proposed CD-GrOPUE, voltammetric techniques were used and two other electrodes were fabricated (GrOPUE and GrPUE) for comparison. The functionalization of the GrO was confirmed by scanning electron microscopy images, energy-dispersive X-ray spectroscopy analysis, and thermogravimetry.

Nanodiamond based surface modified screen-printed electrodes for the simultaneous voltammetric determination of dopamine and uric acid.

The electroanalytical detection of the neurotransmitter dopamine (DA) in the presence of uric acid (UA) is explored for the first time using commercially procured nanodiamonds (NDs). These are electrically wired via surface modification upon screen-printed graphite macroelectrodes (SPEs). The surface coverage of the NDs on the SPEs was explored in order to optimize electroanalytical outputs to result in well-resolved signals and in low limits of detection.

The influence of reaction parameters on complexation of Zn(II) complexes with biopolymeric Schiff bases prepared from chitosan and salicylaldehyde.

Influence of some reactional parameters as mol ratio (Schiff base:metal), solvent, temperature and reaction time were evaluated in order to improve the extension of complexation during the preparation of zinc complexes of biopolymeric Schiff base from chitosan and salicylaldehyde. Zinc(II) complex was used as a model system in order to improve the degree of complexation for further synthesis of different Schiff bases complexes from other aldehydes and metallic centers. The complexation yields for each synthesis were estimated on the basis of the zinc oxide formed after thermal degradation.

Chemical modification of alginate with cysteine and its application for the removal of Pb(II) from aqueous solutions.

It has been synthesized, characterized and tested a new biomaterial AlgS (sodium alginate functionalized with cysteine) to remove Pb(II) in aqueous media. The maximum Pb(II)-sorption capacity of AlgS (Q = 770 mg·g) is between almost two and nine times higher than other alginate-materials reported in the literature. Techniques, such as TGA/DSC, SEM/EDS, BET, FTIR, UV-Vis, XRD and C solid state-NMR have been used to study the chemical-modification of alginate at oxidation and aminofication stages.

Chemical modification of sodium alginate with thiosemicarbazide for the removal of Pb(II) and Cd(II) from aqueous solutions.

A new material (Alg-TSC), based on alginate (Alg) chemically modified with thiosemicarbazide (TSC), has been synthesized and tested as an effective biomaterial to remove Pb(II) and Cd(II) ions in aqueous solutions. The synthesis was carried out by controlling the following steps, i/partial oxidation process of alginate in NaIO to obtain AlgOx, ii/reacting of AlgOx, at 40-45 °C, with TSC in NaBH. Alg-TSC has been characterized by Field Emission Scanning Electron Microscopy (FESEM/EDS), Fourier Transform Infrared Spectroscopy (ATR-IR), solid state C NMR spectroscopy and Point of Zero Charge (pH) measuremenmts.

Thermal behavior of inosine 5'-monophosphate in acidic form and as alkali and alkaline earth salts.

Inosine 5'-monophosphate in acidic form and its lithium, potassium, magnesium, calcium, strontium and barium were prepared from the sodium salt, characterized by elemental analysis and Fourier transform infrared spectroscopy and submitted to thermogravimetry (TG), differential thermal analysis (DTA), differential scanning calorimetry (DSC) and thermogravimetry coupled to infrared spectroscopy (TG-FTIR) of the volatile products evolved during heating. All the salts were hydrated containing from 4 to 7.5 HO.

Synthesis, Characterization and Biological Activities of Biopolymeric Schiff Bases Prepared with Chitosan and Salicylaldehydes and Their Pd(II) and Pt(II) Complexes.

In an attempt to enhance chitosan biological activities, biopolymeric Schiff bases of chitosan and different salicylaldehydes and their palladium(II) and platinum(II) complexes were synthesized and tested. The chemical structures of these derivatives were characterized using ¹H-NMR, FTIR spectroscopy and XPRD. Thermal analysis was done through TGA/DTG-DTA.

Comparative performances of a bare graphite-polyurethane composite electrode unmodified and modified with graphene and carbon nanotubes in the electrochemical determination of escitalopram.

A bare composite graphite-polyurethane electrode (EGPU) and two other modified with graphene (EGPU-GR) and functionalized multi-walled carbon nanotubes (EGPU-CNTs) were prepared and compared regarding their voltammetric response to escitalopran (EST). The modifiers were characterized by Raman spectroscopy and the resulting electrode materials by contact angle measurements with a hydrophilicity character in the ascending order for the composites: GPU > GPU-GR > GPU-CNTs and scanning electron microscopy (SEM). The electroactive areas of the EGPU, EGPU-GR, and EGPU-CNTs were 0.

Synthesis, characterization and biological activity of Cu(II), Ni(II) and Zn(II) complexes of biopolymeric Schiff bases of salicylaldehydes and chitosan.

Schiff bases have been prepared from biopolymer chitosan and salicylaldehyde, 5-methoxysalicylaldehyde, and 5-nitrosalicylaldehyde. Ligands were synthesized in a 1:1.5mol ratio, and their Cu(II), Ni(II) and Zn(II) complexes in a 1:1mol ratio (ligand:metal).

The use of a graphite-castor oil polyurethane composite electrode for the determination of hydroquinone in photographic developers.

The performance of a new graphite-castor oil polyurethane composite electrode in the determination of hydroquinone in photographic developers in a differential pulse voltammetric (DPV) procedure is described. The 60% (graphite, w/w) composite electrode presented good stability, repeatability and accurate response. Limit of detection of 934 nmol L(-1) was observed for hydroquinone within a linear dynamic range from 66 to 530 nmol L(-1).

Evaluation of a carbon paste electrode modified with organofunctionalized amorphous silica in the cadmium determination in a differential pulse anodic stripping voltammetric procedure.

The determination of cadmium using a carbon paste electrode modified with organofunctionalized amorphous silica with 2-benzothiazolethiol was investigated. The Cd(II) oxidation peak was observed around -0.80 V (vs.

Evaluation of a new rigid carbon-castor oil polyurethane composite as an electrode material.

Polyurethane resin derived from castor oil was used to prepare a graphite composite intented to be applied in voltammetry. The best graphite/resin content in the composite was evaluated using cyclic voltammetry. The useful potential window was investigated in different electrolytes with pH ranging from 1 to 13, with good results in relation to the glassy carbon electrode.

Evaluation of a carbon paste electrode modified with organofunctionalised SBA-15 nanostructured silica in the simultaneous determination of divalent lead, copper and mercury ions.

The performance of a carbon paste electrode (CPE) modified with SBA-15 nanostructured silica organofunctionalised with 2-benzothiazolethiol in the simultaneous determination of Pb(II), Cu(II) and Hg(II) ions in natural water and sugar cane spirit (cachaça) is described. Pb(II), Cu(II) and Hg(II) were pre-concentrated on the surface of the modified electrode by complexing with 2-benzothiazolethiol and reduced at a negative potential (-0.80 V).

Graphite-silicone rubber composite electrode: Preparation and possibilities of analytical application.

Composite electrodes were prepared using graphite powder and silicone rubber in different compositions. The use of such hydrophopic materials interned to diminish the swallowing observed in other cases when the electrodes are used in aqueous solutions for a long time. The composite was characterized for the response reproducibility, ohmic resistance, thermal behavior and active area.

Determination of atenolol at a graphite-polyurethane composite electrode.

A bare graphite-polyurethane composite was evaluated as an alternative electrode in the determination of atenolol (ATN) in pharmaceutical formulations. Using a DPV procedure, a linear analytical curve was observed in the 4-100mumolL(-1) range with a LOD=3.16mumolL(-1), without need of surface renewing between successive runs, with recoveries between 95.

Evaluation of the electrochemical behavior and analytical potentialities of a carbon paste electrode modified with a ruthenium (III) piperidinedithiocarbamate complex.

The preparation and electrochemical characterization of a carbon paste electrode modified with bis(N,N-piperidinedithiocarbamate)-mu-tris(N,N-piperidinedithiocarbamate)diruthenium(III) complex, alpha-[Ru2(Pip)5]Cl are described. The best voltammetric response was obtained for a 10% (m/m) alpha-[Ru2(Pip)5]Cl content in the paste, potassium acid phthalate solution pH 4.0 as supporting electrolyte and scan rate of 100 mV s-1.