Aplicação de espectroscopias raman e infravermelho na identificação e quantificação de plastificantes em filmes comerciais de PVC esticável

This paper reports the use of Raman and infrared techniques for the qualitative and quantitative analysis of plasticizers in polyvinylchloride (PVC) commercial films. FT-Raman marker bands were indentified for di-2-ethyl-hexyl adipate (DEHA) and di-2-ethyl-hexyl phthalate (DEHP), allowing for the rapid identification of these species in the commercial film. Quantitative analysis by FT-IR resulted in plasticizers concentrations ranging from 11 to 27% (w/w). Considering the little sample preparation and the low cost of the techniques, FT-IR and FT-Raman are viable techniques for a first assessment of plasticizers in commercial samples.

Effect of the structure of commercial poly(ethylene oxide-b-propylene oxide) demulsifier bases on the demulsification of water-in-crude oil emulsions: elucidation of the demulsification mechanism

Water-in-crude oil emulsions are formed during petroleum production and asphaltenes play an important role in their stabilization. Demulsifiers are added to destabilize such emulsions,however the demulsification mechanism is not completely known. In this paper, the performances of commercial poly(ethylene oxide-b-propylene oxide) demulsifiers were studied using synthetic water-in-oil emulsions and model-systems (asphaltenes in organic solvent). No change in the asphaltene aggregate size induced by the demulsifier was observed. The demulsification performance decreased as the asphaltene aggregate size increased, so it can be suggested that the demulsification mechanism is correlated to the voids between the aggregates adsorbed on the water droplets surface.

Preparation of PVP hydrogel nanoparticles using lecithin vesicles

Hydrogels micro, sub-micro and nanoparticles are of great interest for drug encapsulation and delivery or as embolotherapic agents. In this work it is described the preparation of nano and sub-microparticles of pre-formed, high molecular weight and monomer free poly(N-vinyl-2-pyrrolidone) encapsulated inside the core of lecithin vesicles. The hydrogel particles are formed with a very narrow diameter distribution, of about 800 nm, and a moderate swelling ratio, of approximately 10.

Development of a flotation-spectrophotometric method for determination of cetylpyridinium chloride in pharmaceutical products

A new simple and sensitive flotation-spectrophotometric method for the determination of cetylpyridinium chloride (CPC) is reported. The method is based on the formation of an ion- associate between CPC and Orange II (OR) which is floated in the interface of aqueous phase and n-hexane by vigorous shaking. The aqueous solution was discarded and the adsorbed ion associate on to the wall of a separating funnel was dissolved in a small volume of methanol solvent and its absorbance was measured at 480 nm. The apparent molar absorptivity (Ε) of the ion associate was determined to be 4.12 x 10(5) L mol-1 cm-1. The calibration graph was linear in the concentration range of 15-800 ng mL-1 of CPC with a correlation coefficient of 0.9988. The limit of detection (LOD) was 10.8 ng mL-1. The relative standard deviation (RSD) for determination of 100 and 800 ng mL-1 of CPC was 3.47 and 2.04% (n=7), respectively. The method was successfully applied to the determination of CPC in a commercial mouth washer product.

Poly(ethylene-co-methyl acrylate)/poly(caprolactone) triol blends for drug delivery systems: characterization and drug release

Poly(ethylene-co-methyl acrylate) (EMA) and poly (caprolactone) triol (PCL-T) blends, a biodegradable aliphatic polyester with low molecular weight and moderate water solubility containing diltiazem hydrochloride (DZ) were studied in terms of the thermal and morphological properties, and drug release mechanism. An increase in the PCL-T content in the EMA/PCL-T/DZ films decreased the degree of DZ crystallinity. Drug release from these films is temperature-dependent, and it is possible to modify the drug release rate by adjusting the EMA/PCL-T composition of the blends. The mechanism of drug release is governed by PCL-T melting and PCL-T leaching from EMA matrix.

Poly(o-methoxyaniline) modified electrode for detection of lithium ions

This paper reports the use of an electrode modified with poly(o-methoxyaniline) for detecting lithium ions. These ions are present in drugs used for treating bipolar disorder and that requires periodical monitoring of the concentration of lithium in blood serum. Poly(o-methoxyaniline) was obtained electrochemically by cyclic voltammetry on the surface of a gold electrode. The results showed that the electrode modified with a conducting polymer responded to lithium ions in the concentration range of 1 x 10-5 to 1 x 10-4 mol L-1 . The results also confirmed that the performance of the modified electrode was comparable to that of the standard method (atomic emission spectrophotometry).

Characterization and in vitro release of cyclosporine-A from poly(D,L-lactide-co-glycolide implants obtained by solvent/extraction evaporation

Cyclosporine-A-loaded PLGA implants were developed intended for ocular route. Implants were prepared using solvent extraction/evaporation technique followed by casting of the cake into rods in a heated surface. XRD patterns showed that cyclosporine-A was completely incorporated into PLGA. FTIR and DSC results indicated alterations on drug molecular conformation aiming to reach the most stable thermodynamic conformation at polymer/drug interface. Implants provided controlled/sustained in vitro release of the drug. During the first 7 weeks, the drug release was controlled by the diffusion of the cyclosporine-A; and between 7-23 week period, the drug diffusion and degradation of PLGA controlled the drug release.

Application of ftir in the determination of acrylate content in poly(sodium acrylate-co-acrylamide) superabsorbent hydrogels

Hydrogels have been prepared by free-radical solution copolymerization of acrylamide and sodium acrylate (NaAc), with molar ratio ranging from 25/75 to 80/20, respectively, using methylene bisacrylamide as the crosslinking agent. A FTIR spectroscopy procedure to determine the acrylate/acrylamide ratio in these hydrogels was proposed based on absorbance at 1410 cm-1 (nCOO-) and 2940 cm-1 (nCH and nCH2). A straight line with a good linear correlation coefficient (0.998) was obtained by plotting the acrylate content (Ac%) versus relative absorbance (Arel = A1410/A2940). Results were confirmed by the amount of sodium cation released in acid medium determined by atomic absorption spectrometry.

Monitoring of praseodymium(III) ions in aqueous solutions, soil and sediment samples by a PVC membrane sensor based on a furan-triazole derivative

A furan-triazole derivative has been explored as an ionophore for preparation of a highly selective Pr(III) membrane sensor. The proposed sensor exhibits a Nernstian response for Pr(III) activity over a wide concentration range with a detection limit of 5.2×10-8 M. Its response is independent of pH of the solution in the range 3.0-8.8 and offers the advantages of fast response time. To investigate the analytical applicability of the sensor, it was applied successfully as an indicator electrode in potentiometric titration of Pr(III) solution and also in the direct and indirect determination of trace Pr(III) ions in some samples.

Synthesis, characterization and application of ion imprinted poly(vinylimidazole) for zinc ion extraction/preconcentration with faas determination

In this paper, we describe the synthesis of an ion imprinted polymer (IIP) by homogeneous polymerization and its use in solid-phase to extract and preconcentrate zinc ions. Under optimal conditions (pH 5.0, preconcentration flow rate of 12.0 mL min-1, and eluted with 1.0 mol L-1 HNO3) this procedure allows the determination of zinc with an enrichment factor of 10.2, and with limits of detection and quantification of 1.5 and 5.0 µg L-1, respectively. The accuracy of our results was confirmed by analysis of tap water and certified reference materials: NIST 1570a (Spinach leaves) and NIST 1515 (Apple leaves).

Starch/poly (butylene adipate-co-terephthalate)/montmorillonite films produced by blow extrusion

This study aims to prepare biodegradable films from cassava starch, poly (butylene adipate-co-terephthalate) (PBAT), and montmorillonite (MMT) using blow-extrusion process and analyze the effects of different types and concentrations of MMT on the microstructure, physicochemical, and mechanical properties of the resulting films. The films were produced by blending 30% of PBAT with glycerol (17.5%), starch (49.0-52.5%), and four different types of montmorillonite (Cloisite® Na+, 10A, 15A, and 30B) at two different concentrations (1.75% and 3.5%). All the films prepared in this study showed an increase in the basal spacing of MMT layers. In particular, the films with 10A and 30B showed the highest increase in intercalation basal spacing, suggesting the formation of intercalated composites. The addition of nanoclays decreased the elongation of films. The addition of Cloisite® 10A resulted in films with the lowest WVP values and the highest stability to water adsorption under different RH conditions.

Influence of chloride-mediated oxidation on the electrochemical degradation of the direct black 22 dye using boron-doped diamond and β-PbO2 anodes

The Direct Black 22 dye was electrooxidized at 30 mA cm-2 in a flow cell using a BDD or β-PbO2 anode, varying pH (3, 7, 11), temperature (10, 25, 45 °C), and [NaCl] (0 or 1.5 g L-1). In the presence of NaCl, decolorization rates were similar for all conditions investigated, but much higher than predicted through a theoretical model assuming mass-transport control; similar behavior was observed for COD removal (at pH 7, 25 °C), independently of the anode. With no NaCl, COD removals were also higher than predicted with a theoretical model, which suggests the existence of distinct dye degradation pathways.

NOVEL SUPERABSORBENT HYDROGEL COMPOSITE BASED ON POLY(ACRYLAMIDE-CO-ACRYLATE)/NONTRONITE: CHARACTERIZATION AND SWELLING PERFORMANCE

A novel superabsorbent hydrogel (SH) composite based on a poly(acrylamide-co-acrylate) matrix filled with nontronite (NONT), a Fe(III)-rich member of the smectite group of clay minerals, is described in this manuscript. A variety of techniques, including FTIR, XRD, TGA, and SEM/EDX, were utilized to characterize this original composite. Experimental data confirmed the SH composite formation and suggested NONT was completely dispersed in the polymeric matrix. Additionally, NONT improved the water uptake capacity of the final material, which exhibited fast absorption, low sensitivity to the presence of salt, high water retention and a pH sensitive properties. These preliminary data showed that the original SH composite prepared here possesses highly attractive properties for applications in areas such as the agriculture field, particularly as a soil conditioner.

Utilização de um eletrodo de grafite recoberto com PbO2 incorporado em matriz de PVC como eletrodo indicador em titulações coulométricas

A aplicação de um eletrodo sensível a íons H3O+, obtido pelo recobrimento de um eletrodo de grafite com uma membrana polimérica contendo PbO2 incorporado em uma matriz de PVC (PbO2-PVC), como eletrodo indicador em titulações coulométricas de neutralização, foi investigada. As leituras dos potenciais foram feitas usando o eletrodo indicador de PbO2-PVC e para comparação dos resultados foi usado um eletrodo de vidro combinado (EVC). As curvas de titulação monitoradas com o eletrodo de PbO2-PVC apresentaram características semelhantes àquelas monitoradas com o EVC e os tempos de equivalência obtidos foram concordantes a um nível de confiança de 95%. O eletrodo de PbO2-PVC apresentou resposta linear no intervalo de pH 2 a 12 com inclinação de Nernst de -57,6 ± 0,1 mV/pH (r= 0,9998), sendo o tempo de resposta deste eletrodo bem menor do que aquele obtido com o EVC. O eletrodo de PbO2-PVC é de fácil construção, possui baixo custo e tempo de vida útil superior a 4 meses, equivalente a (pelo menos 1200 determinações por membrana polimérica).