Polypyrrole monolithic extraction phase: From conventional to miniaturized sample preparation techniques.

Monolithic polymers are described as continuous and highly porous materials. They have been gaining popularity as an effective extracting phase for some sample preparation methods, due to their variety of functionalities, such as wide pH range tolerance, good permeability, and its ability to allow changes into their surface. Polypyrrole represents an interesting alternative for the modification in extraction phases due to its well related ability to perform multiple interactions, such as acid-base, π - π, ion exchange, interactions with hydrophobic affinities or polar functional groups. Among the different sample preparation techniques, solid-phase extraction (SPE) is one of the most popular and used; a miniaturized version of SPE is the disposable pipette extraction (DPX). DPX is a recent miniaturized extraction technique that usually employing silica-based sorbents inside a pipette tip (5 or 1 mL). The present study proposes the development of a monolithic extraction phase composed by styrene divinylbenzene (1:1) modified with polypyrrole for SPE and DPX techniques. The efficiency of the material was evaluated in face of the extraction of different samples and analytes, triazine herbicides in water and dexamethasone in synthetic synovial liquid by conventional and miniaturized solid-phase extraction techniques. The extractions performed by SPE and DPX presented absolute recovery values ranging from 74.8 to 105.0%, inter-day precision ranging from 0.6 to 14.0%, and limit of quantification of 0.5 and 5.0 ng.mL-1, respectively. The DPX miniaturized method exhibited results equivalent to the methods reported in the literature for extraction of dexamethasone in synovial fluid samples. Moreover, this technique proved to be quicker and cheaper than SPE, and produced fewer residual volumes, supporting the preference for green chemistry. Monolithic polymers modified with polypyrrole presented to be a feasible alternative extraction phase for miniaturized sample preparation techniques.

Versatile fabrication of paper-based microfluidic devices with high chemical resistance using scholar glue and magnetic masks.

Simple methods have been developed for fabricating microfluidic paper-based analytical devices (µPADs) but few of these devices can be used with organic solvents and/or aqueous solutions containing surfactants. This study describes a simple fabrication strategy for µPADs that uses readily available scholar glue to create the hydrophobic flow barriers that are resistant to surfactants and organic solvents. Microfluidic structures were defined by magnetic masks designed with either neodymium magnets or magnetic sheets to define the patter, and structures were created by spraying an aqueous solution of glue on the paper surface. The glue-coated paper was then exposed to UV/Vis light for cross-linking to maximize chemical resistance. Examples of microzone arrays and microfluidic devices are demonstrated. µPADs fabricated with scholar glue retained their barriers when used with surfactants, organic solvents, and strong/weak acids and bases unlike common wax-printed barriers. Paper microzones and microfluidic devices were successfully used for colorimetric assays of clinically relevant analytes commonly detected in urinalysis to demonstrate the low background of the barrier material and generally applicability to sensing. The proposed fabrication method is attractive for both its ability to be used with diverse chemistries and the low cost and simplicity of the materials and process.

The development of a new disposable pipette extraction phase based on polyaniline composites for the determination of levels of antidepressants in plasma samples.

In the present work, a new stationary phase for disposable pipette extraction (DPX) based on composites of polyaniline and a styrene-divinylbenzene (SD) copolymer was applied to the analysis of fluoxetine and norfluoxetine in plasma samples using liquid chromatography and fluorescence detector (LC-FD). The DPX variables, such as number of draw/eject cycles, sample pH, type and volume of the desorption solvent, were optimized to established the sorption equilibrium and shorten the analysis time. Among the DPX evaluated variables, the higher extraction efficiency were obtained with 200 µL of plasma mixed with 200 µL of borate solution (pH 9), followed by liquid desorption of the drug with 200 µL acetonitrile in a single cycle. The DPX/LC-FD method demonstrated a linear response over the dynamic range from 10 to 1000 ng mL(-1) for fluoxetine and from 80 ng mL(-1) (LOQ) to 1000 ng mL(-1) for norfluoxetine with r(2)=0.997 and 0.998, respectively. The limit of quantification (LOQ) was 10 ng mL(-1) for fluoxetine and 80 ng mL(-1) for norfluoxetine. Based on the analytical validation results, the proposed method can be a useful tool for determining the fluoxetine and norfluoxetine levels in plasma samples from patients receiving therapeutic dosages.

Toxicity of cryoprotectants on Prochilodus lineatus (Valenciennes, 1837) (curimba) embryos in an experimental incubator (Characiformes: Prochilodontidae)

This paper investigated the effect of cryoprotectant substances on Prochilodus lineatus embryos in an experimental incubator. The prospective study applied combinations of polyvinyl alcohol, hydroxyethyl cellulose, gelatin and fetal bovine serum with dimethyl sulfoxide and ethylene glycol in a new experimental incubator. The morphology of embryos, larval viability and the efficiency of experimental incubators in maintaining the quality of embryos were evaluated. This study demonstrates the efficient association between hydroxyethylcellulose and dimethyl sulfoxide as greater viability (p<0.05) was found for embryos (72.9 ± 23.9%). It should also be noted the permeation of cryoprotectants in embryos through the changes found in chorion diameter, embryo diameter and embryo volume comparing the treatments versus control group (water) (p<0.05), this results can help in future cryopreservation protocols. Although the temperature and oxygenation differed between the usual and experimental incubators (p<0.05), the results showed a high fertilization rate (79.6 ± 13.2%) for experimental incubators (p<0.05) which is sufficient for the maintenance of embryos in a cryoprotective environment and effectively allows experimentation for long periods with cryoprotectant substances. Cryopreservation of fish embryos has not been accomplished yet and new approaches are required for understanding the permeability of teleost embryos, especially in Brazilian native species.

Este trabalho avaliou o efeito de substâncias crioprotetoras sobre embriões de Prochilodus lineatus em uma incubadora experimental. O estudo aplicou combinações de álcool polivinílico, hidroxietilcelulose, gelatina e soro fetal bovino com dimetilosulfóxido e etilenoglicol em uma nova incubadora experimental. Foram avaliadas a morfologia dos embriões, a viabilidade larval e a eficiência das incubadoras experimentais na manutenção da qualidade dos embriões. Este estudo demonstra a associação eficiente entre hidroxietilcelulose e dimetilsulfóxido pela maior viabilidade (p<0,05) encontrada para os embriões (72,9 ± 23,9%). Deve-se notar também a permeação dos crioprotetores nos embriões através das alterações encontradas no diâmetro córion, diâmetro do embrião e no volume do embrião comparando os tratamentos ao grupo controle (água) (p<0,05), estes resultados podem ajudar em futuros protocolos de criopreservação. Embora a temperatura e a oxigenação diferiram entre as incubadoras comuns e as experimentais (p<0,05), os resultados mostraram elevada taxa de fertilização (79,6 ± 13,2%) para incubadoras experimentais (p<0,05), o que é suficiente para a manutenção de embriões em ambiente crioprotetor e permite efetivamente a experimentação por longos períodos com substâncias crioprotetoras. A criopreservação de embriões de peixes ainda não foi realizada e novas abordagens são necessárias para a compreensão da permeabilidade dos embriões de teleósteos, especialmente em espécies nativas brasileiras.

Estimating mean crystallite size of magnetite using multivariate calibration and powder x-ray diffraction analysis.

Powder X-ray diffraction patterns for 29 samples of magnetite, acquired using a conventional diffractometer, were used to build PLS calibration-based methods and variable selection to estimate mean crystallite size of magnetite directly from powder X-ray diffraction patterns. The best IPLS model corresponds to the Bragg reflections at 35.4° (h k l = 3 1 1), 43.0° (h k l = 4 0 0), 53.6° (h k l = 4 2 2), and 57.0° (h k l = 5 1 1) in 2θ. The best model was a GA-PLS which produced a model with RMSEP of 0.9 nm, and a correlation coefficient of 0.9976 between mean crystallite sizes calculated using Williamson-Hall approach and the ones predicted by GA-PLS method. These results indicate that magnetite mean crystallite sizes can be predicted directly from Powder X-Ray Diffraction and multivariate calibration using PLS variable selection approach.

Influence of pulse-delay curing on sorption and solubility of a composite resin

The purpose of this study was to evaluate the sorption and solubility of a composite resin (TPH³; Dentsply) cured with halogen light due to different storage media and curing modes. The methodology was based on the ISO 4049 standard. Two independent groups were established according to the storage time (7 days-G1; 60 days-G2). A stainless steel mould (2 mm x 8 mm Ø) was used. The selected curing modes were: I (Conventional - C): 40s - 600 mW/cm²; II (Pulse I - PD): 3 s - 200 mW/cm² + 2 min (delay) + 39 s - 600 mW/cm²; III (Pulse II): 10 s - 200 mW/cm² + 2 min (delay) + 37 s - 600 mW/cm²; IV (Pulse III): 3 s- 600 mW/cm² + 2 min (delay) + 37 s -600 mW/cm². The media used were: distilled water, 75 percent ethanol and 100 percent chlorophorm. Five repetitions were made for each group. The specimens were placed in a desiccator at 37ºC for 24 h and, after that, at 23ºC for 1 h to be weighed until a constant mass (m1) was obtained. The discs were immersed separately into the 3 media for 7 days (G1) and 60 days (G2), and thereafter reweighed (m2). The reconditioning in the desiccator was done until a constant mass (m3) was obtained. Sorption and solubility were calculated and the data of G1 and the sorption data of G2 were subjected to two-way ANOVA and Tukey's tests (p=0.05). The solubility data of G2 were analyzed by Kruskal-Wallis test (p=0.05). For G1 and G2, no statistically significant differences were found in sorption among curing techniques (p>0.05). The solubility values were negative, which means that there was mass gain. Regarding the storage media, in G2 chlorophorm had the highest sorption values. It may be concluded that the curing modes (C and PD I, II and III) did not affect the sorption of the tested composite resin. However, different storage media influenced sorption behavior. The solubility test demonstrated negative data, masking the real solubility.

Influence of pulse-delay curing on sorption and solubility of a composite resin.

The purpose of this study was to evaluate the sorption and solubility of a composite resin (TPH(3); Dentsply) cured with halogen light due to different storage media and curing modes. The methodology was based on the ISO 4049 standard. Two independent groups were established according to the storage time (7 days-G1; 60 days-G2). A stainless steel mould (2 mm x 8 mm Ø) was used. The selected curing modes were: I (Conventional - C): 40s - 600 mW/cm(2); II (Pulse I - PD): 3 s - 200 mW/cm(2) + 2 min (delay) + 39 s - 600 mW/cm(2); III (Pulse II): 10 s - 200 mW/cm(2) + 2 min (delay) + 37 s - 600 mW/cm(2); IV (Pulse III): 3 s- 600 mW/cm(2) + 2 min (delay) + 37 s -600 mW/cm(2). The media used were: distilled water, 75% ethanol and 100% chlorophorm. Five repetitions were made for each group. The specimens were placed in a desiccator at 37 masculineC for 24 h and, after that, at 23 masculineC for 1 h to be weighed until a constant mass (m1) was obtained. The discs were immersed separately into the 3 media for 7 days (G1) and 60 days (G2), and thereafter reweighed (m2). The reconditioning in the desiccator was done until a constant mass (m3) was obtained. Sorption and solubility were calculated and the data of G1 and the sorption data of G2 were subjected to two-way ANOVA and Tukey's tests (p=0.05). The solubility data of G2 were analyzed by Kruskal-Wallis test (p=0.05). For G1 and G2, no statistically significant differences were found in sorption among curing techniques (p>0.05). The solubility values were negative, which means that there was mass gain. Regarding the storage media, in G2 chlorophorm had the highest sorption values. It may be concluded that the curing modes (C and PD I, II and III) did not affect the sorption of the tested composite resin. However, different storage media influenced sorption behavior. The solubility test demonstrated negative data, masking the real solubility.

Modification of silica gel by attachment of 2-mercaptobenzimidazole for use in removing Hg(II) from aqueous media: a thermodynamic approach.

The compound 2-mercaptobenzimidazole (MBI) was attached onto a silica gel surface by homogeneous and heterogeneous routes. Both silica modification methodologies resulted in similar products, named SiM(hom) and SiM(het), respectively. These materials were characterized by surface area, infrared, thermogravimetry, and 13C and 29Si NMR spectroscopy. The ability of these materials to remove divalent mercury from aqueous solution was followed by a series of adsorption isotherms adjusted to a modified Langmuir equation. The maximum number of moles adsorbed was determined to be 1.35+/-0.3 and 1.42+/-0.17 mmolg-1 for SiMhet and SiMhomt, respectively. These interactions were calorimetrically followed and the thermodynamic data showed the following exothermic enthalpic values: -23.04+/-1.4 and -20.08+/-1.2 kJmol-1 for SiMhom and SiMhet, respectively. All liquid/solid interface adsorptions were spontaneous in nature and enthalpically driven.