Protein partitioning in poly(ethylene glycol)/sodium polyacrylate aqueous two-phase systems

The partition of hemoglobin, lysozyme and glucose-6-phospate dehydrogenase (G6PDH) in a novel inexpensive aqueous two-phase system (ATPS) composed by poly(ethylene glycol) (PEG) and sodium polyacrylate (NaPA) has been studied. The effect of NaCl and Na2SO4, pH and PEG molecular size on the partitioning has been studied. At high pH (above 9), hemoglobin partitions strongly to the PEG-phase. Although some precipitation of hemoglobin occurs, high recovery values are obtained particularly for lysozyme and G6PDH. The partitioning forces are dominated by the hydrophobic and electrochemical (salt) effects, since the positively charged lysozyme and negatively charged G6PDH partitions to the non-charged PEG and the strongly negatively charged polyacrylate enriched phase, respectively. (c) 2007 Elsevier B.V. All rights reserved.

The convenient synthesis of a liquid-crystalline polyacrylate with a tetramethylene spacer

A protecting group approach to the synthesis of a liquid crystalline polyacrylate containing a tetramethylene spacer unit is described. This approach prevents the formation of side products obtained when a more direct synthetic pathway is used. The resulting material shows behaviour typical of a nematic liquid crystal polymer.

External polyacrylate-coating as alternative material for preparation of photopolymerized sol-gel monolithic column

Photopolymerized sol-gel monolithic columns for use in capillary electrochromatography were prepared in 125 mu m i.d. polyacrylate-coated fused-silica capillaries. The polyacrylate-coating, unlike the polyimide one, is transparent to the radiation used (approximate to 370 nm), and thus, no coating removal is necessary. This is a very important particularity since intrinsic capillary column characteristics, such as flexibility and mechanical resistance, are unchanged. A mixture containing metacryloxypropyltrimethoxysilane (MPTMS) as the polymeric precursor, hydrochloric acid as the catalyst, toluene as the porogen and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Irgacure 819) as the photoinitiator was irradiated at 370 nm for 20 min inside the capillaries to prepare the columns through sol-gel approach. The versatility and viability of the use of polyacrilate as a new capillary external coating were shown through preparation of two columns under different conditions, which were tested in electrochromatography for separation of standard mixture containing thiourea (marker compound), propylbenzene, phenanthrene and pyrene. (C) 2008 Elsevier B.V. All rights reserved.

Protein partitioning in poly(ethylene glycol)/sodium polyacrylate aqueous two-phase systems

The partition of hemoglobin, lysozyme and glucose-6-phospate dehydrogenase (G6PDH) in a novel inexpensive aqueous two-phase system (ATPS) composed by poly(ethylene glycol) (PEG) and sodium polyacrylate (NaPA) has been studied. The effect of NaCl and Na2SO4, pH and PEG molecular size on the partitioning has been studied. At high pH (above 9), hemoglobin partitions strongly to the PEG-phase. Although some precipitation of hemoglobin occurs, high recovery values are obtained particularly for lysozyme and G6PDH. The partitioning forces are dominated by the hydrophobic and electrochemical (salt) effects, since the positively charged lysozyme and negatively charged G6PDH partitions to the non-charged PEG and the strongly negatively charged polyacrylate enriched phase, respectively. (c) 2007 Elsevier B.V. All rights reserved.

Phase Diagrams of the Aqueous Two-Phase Systems of Poly(ethylene glycol)/Sodium Polyacrylate/Salts

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

External polyacrylate-coating as alternative material for preparation of photopolymerized sol-gel monolithic column

Photopolymerized sol-gel monolithic columns for use in capillary electrochromatography were prepared in 125 mu m i.d. polyacrylate-coated fused-silica capillaries. The polyacrylate-coating, unlike the polyimide one, is transparent to the radiation used (approximate to 370 nm), and thus, no coating removal is necessary. This is a very important particularity since intrinsic capillary column characteristics, such as flexibility and mechanical resistance, are unchanged. A mixture containing metacryloxypropyltrimethoxysilane (MPTMS) as the polymeric precursor, hydrochloric acid as the catalyst, toluene as the porogen and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Irgacure 819) as the photoinitiator was irradiated at 370 nm for 20 min inside the capillaries to prepare the columns through sol-gel approach. The versatility and viability of the use of polyacrilate as a new capillary external coating were shown through preparation of two columns under different conditions, which were tested in electrochromatography for separation of standard mixture containing thiourea (marker compound), propylbenzene, phenanthrene and pyrene. (C) 2008 Elsevier B.V. All rights reserved.

Optimization of photo-polymerized sol gel monolithic stationary phases prepared in polyacrylate-coated fused-silica capillaries for capillary electrochromatography

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Solid-phase microextraction for determination of 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone in water

Solid-phase microextraction, using on-line bis(trimethylsilyl)trifluoroacetamide derivatisation, gas chromatography, and mass spectrometry, was evaluated in the quantification of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) in water samples. Fibres encompassing a wide range of polarities were used with headspace and direct immersion sampling. For the immersion procedure, various parameters affecting MX extraction, including pH, salinity, temperature, and extraction time were evaluated. The optimised method (polyacrylate fibre; 20% Na2SO4; pH 2.0; 60 min; 20 °C) was applied for reservoir chlorinated water samples-either natural or spiked with MX (50 ng L-1 and 100 ng L-1). The recovery of MX ranged from 44 to 72%. Quantification of MX in water samples was done using external standard and the selected ion monitoring mode. Correlation coefficient (0.98%), relative standard deviation (5%), limit of detection (30 ng L-1) and limit of quantification (50 ng L-1) were obtained from calibration curve.

The rheological behavior and surface charging of gelcasting alumina suspensions

Aim of this work is to investigate the effect of monomers containing either carboxylate (ammonium acrylate) or acrylamide (hydroxymethylacrylamide) functional groups on the surface charging and theological behavior of alumina suspensions. The rheological behavior was investigated by changing the concentrations of dispersant (ammonium polyacrylate) and monomers in the suspensions. The zeta potential of alumina suspensions containing each of the different monomers was measured as a function of dispersant additions. The suspension theological behavior varied significantly depending on the monomer type, which could be explained in terms of repulsive forces, pH changes and additive interactions. (C) 2006 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Simultaneous distillation–extraction of high-value volatile compounds from Cistus ladanifer L.

The present paper describes a procedure to isolate volatiles from rock-rose (Cistus ladanifer L.) using simultaneous distillation–extraction (SDE). High-value volatile compounds (HVVC) were selected and the influence of the extraction conditions investigated. The effect of the solvent nature and extraction time on SDE efficiency was studied. The best performance was achieved with pentane in 1 h operation. The extraction efficiencies ranged from 65% to 85% and the repeatability varied between 4% and 6% (as a CV%). The C. ladanifer SDE extracts were analysed by headspace solid phase microextraction (HS-SPME) followed by gas chromatography with flame ionization detection (GC-FID). The HS-SPME sampling conditions such as fiber coating, temperature, ionic strength and exposure time were optimized. The best results were achieved with an 85 µm polyacrylate fiber for a 60 min headspace extraction at 40ºC with 20% (w/v) of NaCl. For optimized conditions the recovery was in average higher than 90% for all compounds and the intermediate precision ranged from 4 to 9% (as CV %). The volatiles α-pinene (22.2 mg g−1 of extract), 2,2,6-trimethylcyclohexanone (6.1 mg g−1 of extract), borneol (3.0 mg g−1 of extract) and bornyl acetate (3.9 mg g−1 of extract) were identified in the SDE extracts obtained from the fresh plant material.

Solid phase microextraction as a short-term sampling technique for BTEX occupational exposure

Solid phase microextraction (SPME) has been widely used for many years in various applications, such as environmental and water samples, food and fragrance analysis, or biological fluids. The aim of this study was to suggest the SPME method as an alternative to conventional techniques used in the evaluation of worker exposure to benzene, toluene, ethylbenzene, and xylene (BTEX). Polymethylsiloxane-carboxen (PDMS/CAR) showed as the most effective stationary phase material for sorbing BTEX among other materials (polyacrylate, PDMS, PDMS/divinylbenzene, Carbowax/divinylbenzene). Various experimental conditions were studied to apply SPME to BTEX quantitation in field situations. The uptake rate of the selected fiber (75 microm PDMS/CAR) was determined for each analyte at various concentrations, relative humidities, and airflow velocities from static (calm air) to dynamic (> 200 cm/s) conditions. The SPME method also was compared with the National Institute of Occupational Safety and Health method 1501. Unlike the latter, the SPME approach fulfills the new requirement for the threshold limit value-short term exposure limit (TLV-STEL) of 2.5 ppm for benzene (8 mg/m(3))

Solid-phase microextraction as short-term sampling technique for BTEX occupational exposure

Solid phase microextraction (SPME) has been widely used for many years in various applications, such as environmental and water samples, food and fragrance analysis, or biological fluids. The aim of this study was to suggest the SPME method as an alternative to conventional techniques used in the evaluation of worker exposure to benzene, toluene, ethylbenzene, and xylene (BTEX). Polymethylsiloxane-carboxen (PDMS/CAR) showed as the most effective stationary phase material for sorbing BTEX among other materials (polyacrylate, PDMS, PDMS/divinylbenzene, Carbowax/divinylbenzene). Various experimental conditions were studied to apply SPME to BTEX quantitation in field situations. The uptake rate of the selected fiber (75 μm PDMS/CAR) was determined for each analyte at various concentrations, relative humidities, and airflow velocities from static (calm air) to dynamic (>200 cm/s) conditions. The SPME method also was compared with the National Institute of Occupational Safety and Health method 1501. Unlike the latter, the SPME approach fulfills the new requirement for the threshold limit value-short term exposure limit (TLV-STEL) of 2.5 ppm for benzene (8 mg/m3).

Polymeeriadsorbenttien käyttö kromatografisessa erotuksessa

Polymeeriadsorbentteja valmistetaan silloittamalla styreeniä, akrylaattia tai fenoliformaldehydiä. Useimmiten ristisilloittajana toimii divinyylibentseeni. Polymeeriadsorbenteissa ei itsessään ole ioninvaihtoryhmiä, joten ne sopivat ionittomien ja heikosti ionisoitujen aineiden adsorptioon. Usein polymeeriadsorbentteja käytetään vaihtoehtona aktiivihiilelle eri sovelluksissa. Työn kirjallisuusosassa on katsaus polymeeriadsorbenttien sovelluksiin lähinnä elintarviketeollisuudessa. Lisäksi siinä selvitetään polymeeriadsorbenttien rakennetta ja synteesimenetelmiä. Kokeellisessa osassa tutkittiin valittujen styreeni- ja akrylaattipohjaisten polymeeriadsorbenttien soveltuvuutta kromatografisen erotuksen stationaarifaasiksi. Kromatografia-ajoissa käytettiin eluenttina vettä, jonka lämpötila oli pääasiassa joko 75 tai 125 °C. Jälkimmäisessä lämpötilassa vesi on paineistettua neste, jota kutsutaan myös alikriittiseksi vedeksi. Malliaineina oli eri sokereita, aminohappoja sekä bentsoehappoa ja bentsyylialkoholia. Kromatografisen soveltuvuuden lisäksi selvitettiin adsorbenttien termistä kestävyyttä ja rakennetta. Termisesti polymeeriadsorbentit kestivät hyvin lämpötiloja 125 °C:eseen saakka. Polymeeriadsorbenteilla, joilla on suuri ominaispinta-ala, on myös suuri adsorptiokapasiteetti. Styreenipohjaiset adsorbentit erottivat kaikkia tutkittuja malliaineita akrylaattipohjaisia paremmin. Jotkut adsorbentit eivät erottaneet mitään tutkituista yhdisteistä. Lämpötilan nostaminen kavensi piikkejä ja nopeutti malliaineiden retentoitumista, mutta ei parantanut erottumista.

Desenvolvimento de um método de MEFS com CG-DIC para determinação de 1,4 dioxana em amostras de cosméticos

A headspace solid-phase microextraction (HS-SPME) for the determination of 1,4 dioxane in cosmetics by gas chromatography is described. A manual SPME holder with 85 µm polyacrylate coating is utilized. The method is determined to have good resolution, satisfactory linerity (correlation coefficient r=0.997 for 0.20-10.00 mg Kg-1 range), a relative standard deviation of 6.3% and a detection limit of 5.00 µg Kg-1. Some cosmectic products were analyzed.

Uso das técnicas de infravermelho e de ressonância magnética nuclear na caracterização da reação ácido-base de um cimento odontológico experimental

Glass ionomer cements (GICs) are products of the acid-base setting reaction between an finely fluoro-alumino silicate glass powder and poly(acrylic acid) in aqueous solution. The sol gel method is an adequate route of preparation of the glasses used to obtain the GICs. The objective of this paper was to compare two powders: a commercial and an experimental and to investigate the structural changes during hardening of the cements by FTIR and Al MAS NMR. These analyses showed that the experimental glass powder reacted with organic acid to form the GICs and it is a promising material to manufacture dental cements.