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131.
Sánchez-Avila J Fernandez-Sanjuan M Vicente J Lacorte S 《Journal of chromatography. A》2011,1218(38):6799-6811
This study describes the development of a multiresidue method based on gas chromatography-electron ionization-tandem mass spectrometry (GC-EI-MS/MS) for the detection of sixteen polycyclic aromatic hydrocarbons (PAHs), five phthalate esters (PEs), seven polychlorinated biphenyls (PCBs), six polybrominated diphenyl ethers (PBDEs), six alkylphenols (APs), three organochlorined pesticides and their isomers or degradation products (OCPs) and bisphenol A in seawater, river water, wastewater treatment plant (WWTP) effluents, sediments and mussels. Solid phase extraction (SPE) was used for the extraction of target analytes in aqueous samples, and ultrasound assisted extraction for solid samples. GC-EI-MS/MS acquisition conditions in selected reaction monitoring (SRM) using two transitions per compound were optimized. In this way, quantification and unequivocal identification of organic micropollutants were performed in compliance with the Decision 2002/657/EC. Good linearity responses with coefficients of determination higher than 0.99 were obtained. Methodological detection limits (MDLs) in seawater ranged from 0.1 to 6 ng L(-1); in river water from 0.1 to 4.8 ng L(-1); in WWTP effluents from 1 to 75 ng L(-1); in sediments from 1 to 150 ng g(-1) and in mussels from 1 to 125 ng g(-1). MDLs and recovery yields were compared with other published methods and similarities or even improvements were achieved. The optimized method was applied to analyze five samples from each matrix collected in coastal areas, showing its potential use for marine pollution monitoring. 相似文献
132.
Raluca M. Albu Iuliana Stoica Ecaterina Avram Emil G. Ioanid Silvia Ioan 《Journal of Solid State Electrochemistry》2014,18(10):2803-2813
Thin gold layers were sputtered on the quaternized polysulfones (containing different tertiary amines—N,N-dimethylethylamine and N,N-dimethyloctylamine, respectively) surfaces unmodified and modified by low-pressure and high-frequency plasma treatment. Adhesion and morphological aspects of complex structures were studied for different gold sputtering and plasma treatment times. Water contact angle, atomic force microscopy, and surface properties reveal that adhesion increases with gold sputtering and plasma treatment times. Values of the mean adhesion force between cantilever and the studied surfaces, measured from AFM investigation, were correlated with quaternized polysulfone structures, modification of hydrophobicity after plasma treatment, and gold deposition on polymer surfaces. 相似文献
133.
Boris Remenec Silvia Dulanská Ľubomír Mátel Ján Bilohuščin 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(1):117-122
The behaviour of 95Zr and 95Nb isotopes on TEVA® resin column was studied. The influence of hydrofluoric, hydrochloric, oxalic and sulphuric acids on the separation and chemical yield of zirconium and niobium was tested. The method is suitable for the separation of 93Zr and 94Nb isotopes from hydrofluoric, hydrochloric and sulphuric acid by using different concentrations of the acid for the load or elutes solutions. Samples from reactor and fuel assemblies such as the control-rod connection rod, shielding/absorber parts of fuel rods, neutron in-core measurement channels, pressure vessel basic construction material and internal cladding, core barrel and reactor protection tube unit were analysed. 相似文献
134.
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136.
Stefano Agnello Michael Brand Mathieu F. Chellat Silvia Gazzola Rainer Riedl 《Angewandte Chemie (International ed. in English)》2019,58(11):3300-3345
The natural phenomenon of drug resistance is a widespread issue that hampers the performance of drugs in many major clinical indications. Antibacterial and antifungal drugs are affected, as well as compounds for the treatment of cancer, viral infections, or parasitic diseases. Despite the very diverse set of biological targets and organisms involved in the development of drug resistance, the underlying molecular mechanisms have been identified to understand the emergence of resistance and to overcome this detrimental process. Detailed structural information on the root causes for drug resistance is nowadays frequently available, so next‐generation drugs can be designed that are anticipated to suffer less from resistance. This knowledge‐based approach is essential for fighting the inevitable occurrence of drug resistance. 相似文献
137.
Silvia Gimnez-Santamarina Salvador Cardona-Serra Juan M. Clemente-Juan Alejandro Gaita-Ario Eugenio Coronado 《Chemical science》2020,11(39):10718
Molecular spin qubits are chemical nanoobjects with promising applications that are so far hampered by the rapid loss of quantum information, a process known as decoherence. A strategy to improve this situation involves employing so-called Clock Transitions (CTs), which arise at anticrossings between spin energy levels. At CTs, the spin states are protected from magnetic noise and present an enhanced quantum coherence. Unfortunately, these optimal points are intrinsically hard to control since their transition energy cannot be tuned by an external magnetic field; moreover, their resilience towards geometric distortions has not yet been analyzed. Here we employ a python-based computational tool for the systematic theoretical analysis and chemical optimization of CTs. We compare three relevant case studies with increasingly complex ground states. First, we start with vanadium(iv)-based spin qubits, where the avoided crossings are controlled by hyperfine interaction and find that these S = 1/2 systems are very promising, in particular in the case of vanadyl complexes in an L-band pulsed EPR setup. Second, we proceed with a study of the effect of symmetry distortions in a holmium polyoxotungstate of formula [Ho(W5O18)2]9− where CTs had already been experimentally demonstrated. Here we determine the relative importance of the different structural distortions that causes the anticrossings. Third, we study the most complicated case, a polyoxopalladate cube [HoPd12(AsPh)8O32]5− which presents an unusually rich ground spin multiplet. This system allows us to find uniquely favorable CTs that could nevertheless be accessible with standard pulsed EPR equipment (X-band or Q-band) after a suitable chemical distortion to break the perfect cubic symmetry. Since anticrossings and CTs constitute a rich source of physical phenomena in very different kinds of quantum systems, the generalization of this study is expected to have impact not only in molecular spin science but also in other related fields such as molecular photophysics and photochemistry.We employ a python computational tool to compare 3 relevant case studies with increasingly complex ground states: vanadyl complexes, Ho(iii) square antiprisms and Ho(iii) cubic structures. 相似文献
138.
Nincevic Gladan Z Ujevic I Milandri A Marasovic I Ceredi A Pigozzi S Arapov J Skejic S 《Molecules (Basel, Switzerland)》2011,16(1):888-899
Dinophysis spp. blooms and related shellfish toxicity events of diarrhetic shellfish poisoning (DSP) have been the most reported toxicity event through the Croatian National monitoring program. With the aim to characterize the DSP toxin profile in shellfish farmed in Croatia, for the first time a complete analysis of the toxin profile of Croatian mussels has been carried out using the LC-MS/MS technique. The obtained results showed okadaic acid (OA) as the main toxin contaminating Croatian mussels at that time. The maximum concentration of OA in shellfish tissue was recorded 12 days after the Dinophysis fortii bloom, thus suggesting that rapid growth of the toxin level in the shellfish occurred in the first week after the bloom while it was slower in the second week. Furthermore, the presence of only OA at concentrations which could endanger human health suggests D. fortii as the main organism responsible for the toxic event that occurred in Lim Bay. The presence of gymnodimine and spirolides in Croatian mussel has been detected for the first time, while the presence of yessotoxin and pectenotoxin-2 is confirmed. 相似文献
139.
Masala S Ahmed T Bergvall C Westerholm R 《Analytical and bioanalytical chemistry》2011,401(10):3305-3315
The efficiency of extraction of polycyclic aromatic hydrocarbons (PAHs) with molecular masses of 252, 276, 278, 300, and 302 Da
from standard reference material diesel particulate matter (SRM 2975) has been investigated using accelerated solvent extraction
(ASE) with dichloromethane, toluene, methanol, and mixtures of toluene and methanol. Extraction of SRM 2975 using toluene/methanol
(9:1, v/v) at maximum instrumental settings (200 °C, 20.7 MPa, and five extraction cycles) with 30-min extraction times resulted in
the following elevations of the measured concentration when compared with the certified and reference concentrations reported
by the National Institute of Standards and Technology (NIST): benzo[b]fluoranthene, 46%; benzo[k]fluoranthene, 137%; benzo[e]pyrene, 103%; benzo[a]pyrene, 1,570%; perylene, 37%; indeno[1,2,3-cd]pyrene, 41%; benzo[ghi]perylene, 163%; and coronene, 361%. The concentrations of the following PAHs were comparable to the reference values assigned
by NIST: indeno[1,2,3-cd]fluoranthene, dibenz[a,h]anthracene, and picene. The measured concentration of dibenzo[a,e]-pyrene was lower than the information value reported by the NIST. The measured concentrations of other highly carcinogenic
PAHs (dibenzo[a,l]pyrene, dibenzo[a,i]pyrene, and dibenzo[a,h]pyrene) in SRM 2975 are also reported. Comparison of measurements using the optimized ASE method and using similar conditions
to those applied by the NIST for the assignment of PAH concentrations in SRM 2975 indicated that the higher values obtained
in the present study were associated with more complete extraction of PAHs from the diesel particulate material. Re-extraction
of the particulate samples demonstrated that the deuterated internal standards were more readily recovered than the native
PAHs, which may explain the lower values reported by the NIST. The analytical results obtained in the study demonstrated that
the efficient extraction of PAHs from SRM 2975 is a critical requirement for the accurate determination of PAHs with high
molecular masses in this standard reference material and that the optimization of extraction conditions is essential to avoid
underestimation of the PAH concentrations. The requirement is especially relevant to the human carcinogen benzo[a]pyrene, which is commonly used as an indicator of the carcinogenic risk presented by PAH mixtures. 相似文献
140.
Venkatramani R Davis KL Wierzbinski E Bezer S Balaeff A Keinan S Paul A Kocsis L Beratan DN Achim C Waldeck DH 《Journal of the American Chemical Society》2011,133(1):62-72
We present evidence for a near-resonant mechanism of charge transfer in short peptide nucleic acid (PNA) duplexes obtained through electrochemical, STM break junction (STM-BJ), and computational studies. A seven base pair (7-bp) PNA duplex with the sequence (TA)(3)-(XY)-(TA)(3) was studied, in which XY is a complementary nucleobase pair. The experiments showed that the heterogeneous charge transfer rate constant (k(0)) and the single-molecule conductance (σ) correlate with the oxidation potential of the purine base in the XY base pair. The electrochemical measurements showed that the enhancement of k(0) is independent, within experimental error, of which of the two PNA strands contains the purine base of the XY base pair. 7-bp PNA duplexes with one or two GC base pairs had similar measured k(0) and conductance values. While a simple superexchange model, previously used to rationalize charge transfer in single stranded PNA (Paul et al. J. Am. Chem. Soc. 2009, 131, 6498-6507), describes some of the experimental observations, the model does not explain the absence of an enhancement in the experimental k(0) and σ upon increasing the G content in the duplexes from one to two. Moreover, the superexchange model is not consistent with other studies (Paul et al. J. Phys. Chem. B 2010, 114, 14140), that showed a hopping charge transport mechanism is likely important for PNA duplexes longer than seven base pairs. A quantitative computational analysis shows that a near-resonant charge transfer regime, wherein a mix of superexchange and hopping mechanisms are expected to coexist, can rationalize all of the experimental results. 相似文献