Development and validation of a liquid chromatography/atmospheric pressure photoionization-tandem mass spectrometric method for the analysis of mycotoxins subjected to commission regulation (EC) No. 1881/2006 In cereals

A sensitive and reliable liquid chromatography/photoionization (APPI) tandem mass spectrometry method has been developed for determining nine selected mycotoxins in wheat and maize samples. The analytes were chosen on the basis of the mycotoxins under EU Commission Regulation (EC) No. 1881/2006, i.e., deoxynivalenol (DON), zearalenone (ZON), aflatoxins (AFs), and ochratoxin A (OTA), and considering the possibility of a near future regulation for T-2 and HT-2 toxins. Mycotoxins were extracted from samples by means of an one-step solvent extraction without any cleanup. The developed multi-mycotoxin method permits simultaneous, simple, and rapid determination of several co-existing toxins separated in a single chromatographic run, in which AFs, T-2 and HT-2 toxin are acquired in positive, while OTA, DON and ZON in negative mode. Although a moderate signal suppression was noticeable, matrix effect did not give significant differences at p = 0.05. Then, calibration in standard solution were used for quantitation. Based on the EU Commission Decision 2002/657/EC, the method was in-house validated in terms of ruggedness, specificity, linearity, trueness, within-laboratory reproducibility, decision limit (CCα) and detection capability (CCβ). For all the analytes, the regression coefficient r ranged between 0.8752 (DON in wheat) and 0.9465 (ZON in maize), biases related to mean concentrations were from −13% to +12% of the nominal spiking level, and the overall within-laboratory reproducibility ranged 3–16%; finally, CCα values did not differ more than 20% and CCβ not more than 42% from their respective maximum limit. Method quantification limits ranged from 1/20 (AFG1) to 1/4 (AFG2 and OTA) the maximum limit established by European Union in the Commission Regulation (EC) No. 1881/2006 and its subsequent amendments.     

Influence of the interface material layers and semiconductor energetic disorder on the open circuit voltage in polymer solar cells

Material layers at electrode/semiconductor interfaces are fundamental for the photovoltaic properties of polymer solar cells. The relationship between open‐circuit voltage ( V_OC ) and the work function ( φ ) of these interface layers is still a matter of debate. Simulations, together with experiments on over more than 20 cell architectures based on P3HT:PC₆₀BM, enabled us to analyze the physical dependence of V_OC on φ . In particular, when the work function of the contacts is well inside the gap we observe that performance depends strongly on even small variations of φ . On the other hand, when it approaches the energy levels of the semiconducting polymers, device operation becomes the most efficient and less sensitive to variations in φ . Furthermore, by varying the Gaussian density of states (DOS) of the active blend we were able to show that V_OC performance depends significantly also on the DOS. Our study based on the simultaneous variation of transport layers represents a promising method to optimize the design and performance of polymer solar cells. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 690–699     

Well-defined transition metal complexes with phosphorus and nitrogen ligands for 1,3-dienes polymerization

This article provides an overview on recent progress in the polymerization of 1,3-dienes catalyzed by transition metal complexes with phosphorus and nitrogen ligands. Polymers having different microstructures (cis-1,4; 1,2; mixed cis-1,4/1,2) and tacticity (iso- or syndiotactic) were obtained from various 1,3-dienes (1,3-butadiene, isoprene, 1,3-pentadienes, 1,3-hexadienes) depending on the catalyst used, clearly suggesting that the catalyst structure (i.e. metal nature, type of ligand) strongly affects the polymerization chemo- and stereoselectivity. However, as indicated by the results obtained in the polymerization of substituted butadienes, a fundamental role in determining the selectivity is also played by the type of monomer: polymers with different structure, some of them completely new, were obtained from different monomers with the same catalyst. All these observations permitted to confirm, and in some cases to improve, the knowledge on the diene polymerization mechanism.     

Determination of ethyl glucuronide in hair samples by liquid chromatography/electrospray tandem mass spectrometry

A method for the determination of ethyl glucuronide (EtG) in hair samples, using liquid chromatography/electrospray tandem mass spectrometry (LC/ESI-MS/MS), was developed and validated. The treatment of hair samples was as follows: to 100 mg of washed (dichloromethane followed by methanol, 1 ml each) and cut (1-2 mm) material, 700 microl of water, 20 microl of internal standard solution (pentadeuterated EtG, D(5)-EtG, 500 microg/l) and 20 microl of methanol were added. Samples were incubated at 25 degrees C overnight and then ultrasonicated for 2 h. Finally, 8 microl of the centrifuged solution (13,000 rpm) were analyzed by LC/ESI-MS/MS in negative ion mode. The surviving ions of EtG and D(5)-EtG were monitored together with the following MRM transitions: m/z 221 --> 75, m/z 221 --> 85 (EtG) and m/z 226 --> 75, m/z 226 --> 85 (D(5)-EtG). The method exhibited a mean correlation coefficient better than 0.9998 over the dynamic range (3-2000 pg/mg). The lower limit of quantification (LLOQ) and the limit of detection (LOD) were 3 and 2 pg/mg respectively. The intra- and interday precision and accuracy were studied at four different concentration levels (3, 5, 56 and 160 pg/mg) and were always better than 7% (n = 5). Matrix effects did not exceed 20%. The method was applied to several hair samples taken from autopsies of known alcoholics, from patients in withdrawal treatment, from social drinkers, from adult teetotalers and from children not exposed to ethanol, with EtG concentrations globally ranging from < or =2 to 4180 pg/mg.     

Sol-gel processing of a bimetallic alkoxide precursor confined in a porous glass matrix: a route to novel glass/metal oxide nanocomposites

In this work we present the utilization of the heterometallic alkoxide [FeCl{Ti(2)(OPr(i))(9)}] as the first sol-gel single-source precursor to achieve nanocomposites made of iron and titanium oxides incorporated into Porous Vycor Glass (PVG). The nanocomposites were prepared by the impregnation of the precursor in a PVG plate followed by hydrolysis reactions. Different samples were obtained by further thermal treatment of the hydrolyzed sample. The nanocomposites were characterized by UV-vis-NIR, Raman and EPR spectroscopies, XRD and TEM. The results indicate that the room-temperature hydrolyzed samples are formed by nanoparticles of FeOOH and brookite-TiO(2) embedded on a glassy matrix. After the heat treatment at temperatures above 900 degrees C, a pseudobrookite Fe(2)TiO(5) was formed. All samples present high transparency and homogeneity. The results showed here indicate that the sol-gel process using the single-source precursor [FeCl{Ti(2)(OPr(i))(9)}] should be a novel and efficient approach to the preparation of nanometric Fe/Ti oxides incorporated into a glassy matrix.     

Incorporation, oxidation and pyrolysis of ferrocene into porous silica glass: a route to different silica/carbon and silica/iron oxide nanocomposites

This work reports the incorporation of ferrocene into a porous silica glass under ambient temperature and atmosphere. After or during the ferrocene incorporation, the spontaneous formation of ferricinium ions was observed by electron paramagnetic resonance (EPR), UV-visible, X-ray absorption near-edge structure (XANES), and 57Fe M?ssbauer measurements. It was shown that the oxidation of ferrocene molecules to ferricinium ions was promoted by air and that the Si-O- groups on the surface of the pores act as counteranions. Pyrolysis of the porous glass/ferricinium material under argon atmosphere and variable temperature yields different glass/carbon nanocomposites, which were subsequently treated with an HF solution in order to remove the glassy fraction. The resulting insoluble carbon materials were characterized by transmission electron microscopy (TEM), Raman, and EPR spectroscopy and consisted of amorphous carbon when the pyrolysis was carried out at 900 or 1000 degrees C and of a mixture of carbon nanotubes and carbonaceous materials at a pyrolysis temperature of 1100 degrees C. When the pyrolysis was conducted under air, the incorporated ferricinium forms alpha-Fe2O3, and the resulting material is a transparent and highly homogeneous glass/iron oxide nanocomposite.     

Analytical approach for monitoring endocrine-disrupting compounds in urban waste water treatment plants

The presence of endocrine-disrupting compounds in influent and effluent water samples from four waste water treatment plants located in Italy was studied. The estrogen-like activity of the water samples was measured using a chemiluminescent recombinant yeast assay which is based on genetically engineered yeast cells that express the human estrogen receptor. This receptor, once activated, elicits the expression of the reporter gene lac-Z and, consequently, the production of β-galactosidase, which is then measured by chemiluminescence. To control and minimize sample matrix effects, an external control based on a modified yeast strain stably expressing β-galactosidase was developed and also used in the assay. Rapid and sensitive chemiluminescent enzyme immunoassays were also developed and validated for the quantification of 17β-estradiol, estrone, and estriol in waste water samples. Results from both methods were compared with a reference high-performance liquid chromatography and electrospray ionization tandem mass spectrometry (HPLC ESI-MS-MS) method developed for the quantification of natural estrogens. The recombinant yeast assay revealed a significant estrogenic activity in the influent samples, ranging from 80 to 400 pmol/L 17β-estradiol equivalents (EEQ), which was reduced by 70–95 % in the effluent samples. The yeast assay also showed a systematic 20–30 % overestimation of estrogenic activity relative to the HPLC ESI-MS-MS method, suggesting the presence of other compounds in the samples with estrogenic activity. The chemiluminescent enzyme immunoassays showed the presence of estrogens in the influent samples (mean concentrations: 350–450 pmol/L for estrone, 5–100 pmol/L for 17β-estradiol, 25–300 pmol/L for estriol), with significantly lower concentrations detected in the respective effluent samples. The waste water treatment was able to reduce natural estrogen concentrations by 40–95 %, although a high variability was observed. The enzyme immunoassay data correlated well with data obtained by the HPLC ESI-MS-MS method. Although the recombinant yeast assay represents a useful tool for a first-level screening of estrogenic activity due to its simplicity and high analytical throughput, sample matrix effects observed in waste water of industrial origin were found to strongly affect the yeast cells response, even when properly corrected for using the external control, thereby limiting its use to urban waste water. Its integration with chemiluminescent enzyme immunoassays would improve its performance by reducing false negative results, thereby enabling its use in extensive studies monitoring for the presence of endocrine-disrupting compounds in urban treatment plant effluents.     

Regeneration of total RNA purification silica-based columns

Silica-based columns are largely used in RNA purification, allowing fast extractions and good yields of high quality nucleic acid, but their major limitation is the high cost. The reuse of such columns, although desirable, is not recommended because of residual amounts of material from the previous sample trapped in the column matrix, which might be released during further purification. Thus, recycling does need previous complete removal of any detectable RNA trace, but to date no protocol which allows decontamination and reuse is available.We report a very rapid decontamination procedure, based on treatment with warm alkaline solution containing Triton X-100, which ensures no RNA carry-over, and allows the recycling of columns without impairment of their efficiency in high-quality RNA purification even after several regeneration rounds.