Benzodipyrrole derivates as new ionophores for anion-selective electrodes: improving potentiometric selectivity towards divalent anions

Two open substituted benzodipyrroles were tested as hydrogen-bond-forming anion ionophores for the development of anion-selective electrodes. These compounds were incorporated in plasticized polymeric membranes with different plasticizers, using different membrane compositions to explore their response towards several anions. The electrodes constructed with membranes containing 2-nitrophenyl octyl ether and a 0.5 molar ratio ionic additive/ionophore showed pronounced anti-Hofmeister behaviour, providing a significantly enhanced response towards the divalent anions sulfate, sulfite, thiosulfate and oxalate. The selected electrodes were also evaluated in terms of detection limits and selectivity. ¹H NMR experiments were carried out in an attempt to explain some aspects of the behaviour observed.     

Ethanol Production from Residual Wood Chips of Cellulose Industry: Acid Pretreatment Investigation,Hemicellulosic Hydrolysate Fermentation,and Remaining Solid Fraction Fermentation by SSF Process

Current research indicates the ethanol fuel production from lignocellulosic materials, such as residual wood chips from the cellulose industry, as new emerging technology. This work aimed at evaluating the ethanol production from hemicellulose of eucalyptus chips by diluted acid pretreatment and the subsequent fermentation of the generated hydrolysate by a flocculating strain of Pichia stipitis. The remaining solid fraction generated after pretreatment was subjected to enzymatic hydrolysis, which was carried out simultaneously with glucose fermentation [saccharification and fermentation (SSF) process] using a strain of Saccharomyces cerevisiae. The acid pretreatment was evaluated using a central composite design for sulfuric acid concentration (1.0–4.0 v/v) and solid to liquid ratio (1:2–1:4, grams to milliliter) as independent variables. A maximum xylose concentration of 50 g/L was obtained in the hemicellulosic hydrolysate. The fermentation of hemicellulosic hydrolysate and the SSF process were performed in bioreactors and the final ethanol concentrations of 15.3 g/L and 28.7 g/L were obtained, respectively.     

Solution structures of fluorescent Zn(II) complexes with bis(naphthyl amide)-EDTA

Two EDTA-based bichromophoric isomers form Zn(II) complexes that exhibit distinct fluorescent behaviors; the ligands are abbreviated as (edta1nap)H₂ and (edta2nap)H₂, each of which consists of an EDTA chain linked to two 1-naphthyl or 2-naphthyl groups. The coordination chemistry of these complexes was studied by UV-Vis, fluorescence and ¹H NMR. The formation constants and the inherent emission intensities were determined by the pH dependence of the emission spectra; the species of the most intense emission is ML(OH) for L = (edta1nap)²⁻, and ML for (edta2nap)²⁻. The ¹H NMR of Zn-(edta1nap)²⁻ exhibits two sets of signals due to a slow exchange between two equivalent coordination geometries, whereas Zn-(edta2nap)²⁻ undergoes a fast exchange to show a single set of NMR signals. The spin-lattice relaxation time T₁ determined for the isostructural Mn(II) complexes shows that the naphthyl proton closest to the metal ion is H(8) in the (edta1nap)²⁻ complex, and H(3) in the (edta2nap)²⁻ complex. The two ligands differ only in the substitution position of the naphthyl group, but this apparently small difference leads to the notable difference in structural, dynamic, and consequent emission-spectral properties of their metal complexes as a result of the steric and size effects of the aromatic rings.     

Binap-gold(I) versus Binap-silver trifluoroacetate complexes as catalysts in 1,3-dipolar cycloadditions of azomethine ylides

The 1,3-dipolar cycloaddition between azomethine ylides and alkenes is efficiently catalysed by [{(S(a))-Binap-Au(tfa)}(2)] (Binap=2,2'-bis(diphenylphosphino)-1,1'-binaphthyl; tfa=trifluoroacetyl). Maleimides, 1,2-bis(phenylsulfonyl)ethylene, chalcone and nitrostyrene were suitable dipolarophiles even when using sterically hindered 1,3-dipole precursors. The results obtained in these transformations improve the analogous ones obtained in the same reactions catalysed by [Binap-Ag(tfa)]. In addition, computational studies have also been carried out to demonstrate both the high enantioselectivity exhibited by the chiral gold(I) complex, and the non-linear effect observed in this transformation.     

High-performance liquid chromatography-diode array detection-electrospray ionization multi-stage mass spectrometric screening of an insect/plant system: the case of Spodoptera littoralis/Lycopersicon esculentum phenolics and alkaloids

High-performance liquid chromatography-diode array detection-electrospray ionization multi-stage mass spectrometry (HPLC-DAD-ESI-MS(n)) is considered to be a very valuable tool for the characterization of compounds found in trace amounts in natural matrices, as their previous isolation and clean-up steps can be avoided. Micro-scale separation increases the potential of this analytical technique, allowing the determination of compounds in reduced samples. Spodoptera littoralis represents a major challenge to Solanaceae plants, as it is one of the most deleterious pests. The S. littoralis/Lycopersicon esculentum system was studied for the first time concerning glycoalkaloids and phenolics. Using HPLC-DAD-ESI-MS(n) we were able to characterize 15 phenolic compounds in L. esculentum leaves. Nine of them are reported for the first time. Some differences were found between leaves of cerasiforme and 'Bull's heart' varieties. However, in the materials of S. littoralis (larvae, adults, exuviae and excrements) reared in both L. esculentum leaves no phenolics were identified. α-Tomatine was the main glycoalkaloid in the host plant. The glycoalkaloid composition of the different S. littoralis materials was distinct, with α-tomatine and dehydrotomatine being the main detected compounds in larvae and excrements. These results add knowledge to the ecological interaction in this insect/plant duo, for which it is hard to obtain considerable sample amounts.     

Surface and bulk cotton fibre modifications: plasma and cationization. Influence on dyeing with reactive dye

The surface of cotton fabrics was functionalized through corona plasma treatments and/or by cationising the whole of the fibre with an epihalohydrin. The effects of both treatments, individually and in combination are analyzed through wettability studies, by X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), and also by dyeing studies with an hetero bis functional reactive dye. Plasma improved wetting properties, exhaustion of the dyebaths and K/S_corr of the fabrics through surface functionalisation. Cationising of the cotton highly increased the exhaustion of the dyebaths and produced a dramatic improvement in K/S_corr. Plasma treatment previous to cationising increased the impregnation of the fabrics, but the effects of both treatments on dyeing parameters are additive only in column water rise and generally the effects obtained by cationising with the epihalohydrin prevail. The differences between both treatments are discussed in terms of surface functionalisation of the cotton fibres.     

Synthesis and characterization of novel amino cellulose esters

The homogeneous conversion of cellulose dissolved in N-methyl-2-pyrrolidone/LiCl and 1-N-butyl-3-methylimidazolium chloride with N-methyl-2-pyrrolidone, ε-caprolactam, N-methyl-ε-caprolactam, and N-methyl-2-piperidone in the presence of p-toluenesulphonic acid chloride was studied. Depending on the reaction conditions, novel cellulose esters with degree of substitution (DS) values ranging from 0.12 to 1.17 could be prepared. The structure of the amino group containing cellulose esters was elucidated by elemental analysis, FTIR- and NMR spectroscopy. NMR spectroscopy revealed an almost complete esterification of position 6 of the anhydroglucose unit at DS of 1. The conversion can be conducted between room temperature and 40 °C, while side-reactions became predominant at 60 °C. Starting with DS of 0.24, the samples were soluble both in water and dimethyl sulphoxide. The derivatives described are capable of forming polyelectrolyte complexes. The samples were stable at room temperature in aqueous solution at pH 2 and 7. Lower viscosities were found for samples with higher DS in aqueous solution at comparable molar mass.     

A disposable electrochemical immunosensor for prolactin involving affinity reaction on streptavidin-functionalized magnetic particles

A novel electrochemical immunosensor was developed for the determination of the hormone prolactin. The design involved the use of screen-printed carbon electrodes and streptavidin-functionalized magnetic particles. Biotinylated anti-prolactin antibodies were immobilized onto the functionalized magnetic particles and a sandwich-type immunoassay involving prolactin and anti-prolactin antibody labelled with alkaline phosphatase was employed. The resulting bio-conjugate was trapped on the surface of the screen-printed electrode with a small magnet and prolactin quantification was accomplished by differential pulse voltammetry of 1-naphtol formed in the enzyme reaction using 1-naphtyl phosphate as alkaline phosphatase substrate. All variables involved in the preparation of the immunosensor and in the electrochemical detection step were optimized. The calibration plot for prolactin exhibited a linear range between 10 and 2000 ng mL(-1) with a slope value of 7.0 nA mL ng(-1). The limit of detection was 3.74 ng mL(-1). Furthermore, the modified magnetic beads-antiprolactin conjugates showed an excellent stability. The immunosensor exhibited also a high selectivity with respect to other hormones. The analytical usefulness of the immnunosensor was demonstrated by analyzing human sera spiked with prolactin at three different concentration levels.     

Using liquid crystals as a readout system in urinary albumin assays

Detecting human serum albumin (HSA) in urine samples is a standard procedure for the diagnosis of kidney problems and the prognosis of patients with chronic kidney diseases (CKDs). In this study, we developed a HSA assay by incorporating a thin layer of liquid crystals (LCs) as a readout system such that the presence of HSA in urine samples can be detected as optical signals. In combination with dilution protocols, this assay can be used to estimate the concentration range of HSA simply by counting the number of bright spots. Our results show that the assay can detect HSA at concentrations as low as 15 μg mL(-1). It is anticipated that this assay can provide a faster and simpler alternative for the diagnosis and prognosis of patients with kidney diseases.     

Fully automated determination of parabens, triclosan and methyl triclosan in wastewater by microextraction by packed sorbents and gas chromatography-mass spectrometry

A fully automated method for the determination of triclosan (TCS), its derivative methyl triclosan (MeTCS) and six parabens (esters of 4-hydroxybenzoic acid) including branched and linear isomers of propyl (i-PrP and n-PrP) and butyl paraben (i-BuP and n-BuP) in sewage water samples is presented. The procedure includes analytes enrichment by microextraction by packed sorbent (MEPS) coupled at-line to large volume injection-gas chromatography-mass spectrometry (LVI-GC-MS). Under optimised conditions, compounds were extracted from 2 mL samples, adjusted at pH 3, using a C18 MEPS-sorbent. Adsorbed analytes were eluted directly into the Programmable Temperature Vaporizer (PTV) injector of the chromatograph with 2×25 μL of ethyl acetate. They were quantified using standard solutions in ultrapure water submitted to the same sample enrichment process as real sewage water samples. After signal normalisation using isotopic labelled species as internal surrogates, no differences were noticed among the extraction efficiency for sewage and ultrapure water; moreover, the proposed method reported lineal calibration curves from 0.1 to 10 ng mL(-1), relative standard deviations (%RSD) between 2 and 7.1% and limits of detection (LODs) varying from 0.001 to 0.015 ng mL(-1) in ultrapure water and from 0.02 to 0.59 ng mL(-1) in the most complex sample (raw wastewater).