Analysis of aldehydes via headspace SPME with on-fiber derivatization to their O-(2,3,4,5,6-pentafluorobenzyl)oxime derivatives and comprehensive 2D-GC-MS

A method for the analysis of the homologous series of alkanals, (E)-2-alkenals, and (E,E)-2,4-alkadienals is described utilizing a headspace solid-phase microextraction (HS-SPME) step and on-fiber derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) hydrochloride. Oxime derivatives formed on the fiber are desorbed in the gas chromatographic injector and analyzed by comprehensive 2-D GC coupled to quadrupole MS (GC x GC-qMS). Selecting specific fragment ions within the electron impact mass spectra of the oxime derivatives provides a suitable method for the target analysis of these aldehyde classes, which furthermore benefits from the increased separation efficiency by GC x GC. The analysis of higher molecular weight aldehydes is described in wine and grape seed oil as examples. Quantification of the aldehydes utilizes a stable isotope dilution analysis (SIDA) assay with octan-d(16)-al as isotopomeric internal standard. Besides the selectivity and sensitivity of aldehyde analysis using PFBHA derivatives, critical aspects on background level contamination and repeatability of the sample preparation method are discussed. Optimization of GC x GC-qMS parameters allowed a considerable saving of the cryogenic medium, involving additional (unmodulated) conditioning runs, rendering the method more amenable to routine analysis.     

Octyl‐modified magnetic graphene as a sorbent for the extraction and simultaneous determination of fragrance allergens,musks, and phthalates in aqueous samples by gas chromatography with mass spectrometry

An effective, simple, and low‐cost sample preparation method based on dispersive SPE followed by GC with MS is developed for the multianalyte determination of fragrance allergens, musks, and phthalates, at sub‐ppb levels. The extraction procedure is based on a novel magnetic graphene sorbent, which is functionalized with octylamine, taking advantage of the functionalization's hydrophobic properties and π–π interactions with the analytes. Two alkyl amines, the octylamine and octadecylamine are studied to introduce alkyl chains in the basal plane of graphene. Magnetic graphene‐ octadecylamine is proved to be highly hydrophobic to such a degree that is hard to disperse in the bulk aqueous matrixes. Because of this behavior, its extraction efficiency for the target analytes is low. The synthesis and applicability of the magnetic graphene‐octylamine as more favored sorbent are optimized in terms of the most determining experimental conditions. The detection and quantification limits, which are calculated based on S/N ratio of 3 and 10, respectively, ranged from 0.29 to 3.2 ng L^?1 and from 0.89 to 9.6, respectively. The dispersive SPE is successfully applied to routine analysis for the determination of the target analytes in samples from municipal treatment plant of Ioannina (Greece), from Pamvotis Lake and baby bathwater. The reproducibility of the spiked biological treatment plant water sample is evaluated and the relative standard deviation values range between 2.1 and 9.4%.     

Multipurpose organically modified carbon nanotubes: from functionalization to nanotube composites

We show that covalent functionalization of carbon nanotubes (CNTs) via 1,3-dipolar cycloaddition is a powerful method for enhancing the ability to process CNTs and facilitating the preparation of hybrid composites, which is achieved solely by mixing. CNTs were functionalized with phenol groups, providing stable dispersions in a range of polar solvents, including water. Additionally, the functionalized CNTs could easily be combined with polymers and layered aluminosilicate clay minerals to give homogeneous, coherent, transparent CNT thin films and gels.     

A signal filtering method for improved quantification and noise discrimination in fourier transform ion cyclotron resonance mass spectrometry-based metabolomics data

Direct-infusion electrospray-ionization Fourier transform ion cyclotron resonance mass spectrometry (DI ESI FT-ICR MS) is increasingly being utilized in metabolomics, including the high sensitivity selected ion monitoring (SIM)-stitching approach. Accurate signal quantification and the discrimination of real signals from noise remain major challenges for this approach, with both adversely affected by factors including ion suppression during electrospray, ion—ion interactions in the detector cell, and thermally-induced white noise. This is particularly problematic for complex mixture analysis where hundreds of metabolites are present near the noise level. Here we address relative signal quantification and noise discrimination issues in SIM-stitched DI ESI FT-ICR MS-based metabolomics. Using liver tissue, we first optimized the number of scans (n) acquired per SIM window to address the balance between quantification accuracy versus acquisition time (and thus sample throughput); a minimum of n = 5 is recommended. Secondly, we characterized and computationally-corrected an effect whereby an ion’s intensity is dependent upon its location within a SIM window, exhibiting a 3-fold higher intensity at the high m/z end. This resulted in significantly improved quantification accuracy. Finally, we thoroughly characterized a three-stage filter to discriminate noise from real signals, which comprised a signal-to-noise-ratio (SNR) hard threshold, then a “replicate” filter (retaining only peaks in r-out-of-3 replicate analyses), and then a “sample” filter (retaining only peaks in >s% of biological samples). We document the benefits of three-stage filtering versus one- and two-stage filters, and show the importance of selecting filter parameters that balance the confidence that a signal is real versus the total number of peaks detected.     

A Low-Complexity PTS-based PAPR Reduction Technique for OFDM Signals without Transmission of Side Information

Increased peak-to-average power ratio (PAPR) imposes a design challenge for orthogonal frequency division multiplexing-based signals. An efficient technique to address the increased PAPR problem is the partial transmit sequences (PTS) approach. A significant drawback of PTS is the fact that it multiplies the transmitted symbol with weighting factors selected by the transmitter. Since the weighting factors are required for decoding, they are explicitly transmitted, in most cases. This paper proposes a new low-complexity technique for retrieving the weighting factors in the receiver. The proposed decoder uses the predefined values of pilot tones and explores all the permissible combinations of weighting factors in order to identify the factor combination employed by the transmitter. The proposed decoder requires no additional pilot tones or explicit transmission of side information, therefore no data rate loss is implied. Furthermore this paper presents a digital very large scale integration implementation of the proposed PTS decoder and demonstrates its low-power properties.     

Effect of [Fe(CN)6]4- substitutions on the spin-flop transition of a layered nickel phyllosilicate

A 3 to 1 Ni/Si antiferromagnetic layered phyllosilicate, Ni(3)Si(C(3)H(6)NH(3))F(0.65)O(1.9)(OH)(4.45)(CH(3)COO)(1.1)·xH(2)O, was modified with K(4)[Fe(CN)(6)]·3H(2)O. This compound retained its ordering as proved by X-ray diffraction, while infrared spectra revealed the presence of [Fe(CN)(6)](4-) groups and X-ray photoelectron spectroscopy showed that the latter partially substitute the acetate groups. Both the parent and the modified compound are canted antiferromagnets with an anisotropy perpendicular to the layers and show spin-flop transitions. For the parent compound, a single step spin-flop occurs at H = 24 kOe. The modified compound shows increased antiferromagnetic canting and a two-step transition (H(1) = 24 kOe, H(2) = 48 kOe). These results testify to the existence of competing interactions that depend sensitively on the grafted species.     

Pesticide use,environmental spillovers and efficiency: A DEA risk-adjusted efficiency approach applied to Dutch arable farming

Pesticides are widely used by crop producers in developed countries to combat risk associated with pests and diseases. However, their indiscriminate use can lead to various environmental spillovers that may alter the agricultural production environment thus contributing to production risk. This study utilises a data envelopment analysis (DEA) approach to measure performance of arable farms, incorporating pesticides’ environmental spillovers and output variance as undesirable outputs in the efficiency analysis and taking explicitly into account the effect of pesticides and other inputs on production risk. The application focuses on panel data from Dutch arable farms over the period 2003–2007. A moment approach is used to compute output variance, providing empirical representations of the risk-increasing or -decreasing nature of the used inputs. Finally, shadow values of risk-adjusted inputs are computed. We find that pesticides are overused in Dutch arable farming and there is a considerable evidence of the need for decreasing pesticides’ environmental spillovers.     

Methanolysis as a route to gallium(III) clusters: synthesis and structural characterization of a decanuclear molecular wheel

Treatment of a methanolic solution of gallium(III) nitrate with lithium hydroxide in the presence of benzilic acid resulted in the decanuclear cluster [Ga(OMe)2{O2CC(OH)Ph2}]10 (1). The metal and the organic components have assembled to form a cyclic molecule that adopts the structure of a wheel. The 10 Ga(III) ions are approximately coplanar and are coordinated in a distorted octahedral manner by six oxygen atoms. The integrity of the molecular wheel is retained in solution, as evidenced by the 1NMR spectrum of 1 in DMSO-d6, while no signal in the 71Ga NMR could be detected.     

A Broadband Monitoring System for Electromagnetic-Radiation Assessment

A broadband monitoring system for measuring the total electric field radiated from broadcasting (radio, TV) and communications (mobile telephony, TETRA, WLAN) systems is presented. The system has been implemented for recording the field on a 24-hour basis. It has an omnidirectional sensor antenna and the appropriate electronic circuits. The heart of the system is a low-power, eight-bit RISC Microchip microcontroller, running at 10 MHz. Various digital and analog peripherals are connected to the microcontroller. The system can send the data to a personal computer through a USB interface, and can communicate through a GSM modem. Low cost and high reliability render the system inexpensive for the deployment of electromagnetic radiation-monitoring networks, and make it trustworthy for the public. Several tests of the sensor's pattern, the linearity of the response, and the frequency response have shown that the system can be successfully compared with commercially available systems.