Structures of the high-temperature solid phases of the odd-numbered fatty acids from tridecanoic acid to tricosanoic acid

Crystal structures of the high-temperature phases of odd-numbered fatty acids (C(n)H(2n-1)OOH) from tridecanoic acid (C(13)H(25)OOH) to tricosanoic acid (C(23)H(45)OOH) are presented in this article. They have been determined from high-quality X-ray powder-diffraction patterns. Two types of high-temperature phases are adopted: one monoclinic A2/a with Z=8 for the fatty acids with n=13 and n=15, denoted as C', and one monoclinic P2(1)/a with Z=4 for the longer-chain fatty acids, denoted as C'. It appears that the packing arrangement of the alkyl chains and of the carboxyl groups is similar in all of the structures. However, the arrangement at the methyl-group interface differs between the C' and C' forms. A survey of the intermolecular interactions involved in these polymorphs coupled with a study of the effects of temperature on the structures have led us to a better understanding of the arrangement of the molecules within the high-temperature solid phases of odd-numbered fatty acids.     

Pesticide analysis in rose wines by micellar electrokinetic chromatography

In this work, the determination of 11 pesticides (pirimicarb, metalaxyl, pyrimethanil, procymidone, nuarimol, azoxystrobin, tebufenozide, fenarimol, benalaxyl, penconazole, and tetradifon) in rose wines by micellar EKC (MEKC) using reversed electrode polarity stacking mode (REPSM) as online preconcentration strategy is described. The MEKC buffer consisted of 100 mM sodium tetraborate and 30 mM SDS at pH 8.5 with 6% v/v 1-propanol. A solid-phase microextraction (SPME) procedure using PDMS/divinylbenzene (PDMS/DVB) fibers was applied to extract the selected pesticides from the rose wine samples. The comparison between the calibration curves obtained from hydroalcoholic solutions (12% v/v ethanol) and from rose wines (matrix matched calibration) showed the existence of a strong matrix effect. Furthermore, a comparison with calibration curves obtained with white wine samples also showed significant differences for most of the analyzed pesticides. As a result, a matrix matched calibration was developed. Quantitative extraction from spiked wine samples was carried out in triplicate at two levels of concentration (range 0.18-6.00 mg/L). LODs between 0.040 and 0.929 mg/L were achieved, which are below the maximum residue limits (MRLs) established for wine grapes (except for pirimicarb) by the EU and Spain legislation as well as by the Codex Alimentarius. The established method - which is solvent free, cost effective, and fast - was also applied to the analysis of several homemade rose wine samples and a commercial one. Two of the selected pesticides were found in some of the analyzed samples.     

Iron protoporphyrin-modified monolithic support for on-line preconcentration of angiotensin prior to CE analysis

An on-line preconcentration method using a polymeric monolithic support is proposed for the retention of the decapeptide angiotensin I and its subsequent analysis by CZE. Monolithic capillary columns were prepared in fused-silica (FS) capillaries of 150 microm id by ionizing radiation-initiated in situ polymerization and cross-linking of diethylene glycol dimethacrylate and glycidyl methacrylate, and chemically modified with iron protoporphyrin IX (Fe-ProP). Monolithic microcolumns (8 mm long) were coupled on-line to the inlet of the separation capillary (FS capillary, 75 microm id x10 cm from the inlet to the microcolumn and 27 cm from the microcolumn to the detector). Angiotensin I was released from the sorbent by a 50 mM sodium phosphate, pH 2.5/ACN, 75:25 v/v solution and then analyzed by CZE with UV absorption detection at 214 nm. The concentration LOQ (CLOQ) was 0.5 ng/mL. The Fe-ProP-derivatized monolithic microcolumn coupled to the separation capillary exhibited a high retention capacity for peptide angiotensin I, and showed as much as 10,000-fold improvement in concentration sensitivity.     

In-line liquid-phase microextraction for selective enrichment and direct electrophoretic analysis of acidic drugs

This work describes an efficient in-line extraction-preconcentration unit coupled to the electrophoretic capillary based on a liquid-phase microextraction (LPME) process, which can be directly assembled to the cartridge of the commercial CE equipment. The unit permits analyte extraction, preconcentration and electrophoretic separation to be automatically performed in the commercial CE equipment without the need for additional hardware or software. This new approach was usefully used for the separation and determination of nonsteroidal anti-inflammatory drugs in human urine permitting at least to analyze 30 consecutive real samples. The LODs were lower than 2 microg/L and the reproducibility, expressed as RSD, was 3.1% for the same unit and only 4.8% between different units.     

Microwave-assisted reactions in heterocyclic compounds with applications in medicinal and supramolecular chemistry

Microwave irradiation has been successfully applied in organic chemistry. Spectacular accelerations, higher yields under milder reaction conditions and higher product purities have all been reported. Indeed, a number of authors have described success in reactions that do not occur under conventional heating and modifications in selectivity (chemo-, regio- and stereoselectivity) have even been reported. Recent advances in microwave-assisted combinatorial chemistry include high-speed solid-phase and polymer-supported organic synthesis, rapid parallel synthesis of compound libraries, and library generation by automated sequential microwave irradiation. In addition, new instrumentation for high-throughput microwave-assisted synthesis continues to be developed at a steady pace. The impressive speed combined with the unmatched control over reaction parameters justifies the growing interest in this application of microwave heating. In this review we highlight our recent advances in this area, with a particular emphasis on cycloaddition reactions of heterocyclic compounds both with and without supports, applications in supramolecular chemistry and the reproducibility and scalability of organic reactions involving the use of microwave irradiation techniques.     

Reproducibility and scalability of solvent-free microwave-assisted reactions: from domestic ovens to controllable parallel applications

The heating of different parallel arrays in domestic ovens offers the possibility to perform multiple reactions in one irradiation experiment, blending the advantages of microwave heating technology and parallel chemistry. However, they are usually performed without an appropriate temperature control; thus, reproducibility becomes a major issue limiting the application of such reactions. This is exemplified when working at a different scales or using different instruments. For the first time a typical solvent-free reaction described in a domestic oven has been reproduced in monomode reactor, scaled up in a controlled multimode oven and reproduced in parallel, 24 reactions were carried out in a well plate. Parallel reactions were performed in a Weflon multiwell plate to assure identical conditions for each individual reaction. As many reactions under microwave irradiation have been performed in solvent-free conditions, this result opens new possibilities in reproducibility, scalability and combinatorial chemistry and permits to take advantage of many synthetic procedures described in domestic ovens.     

Electrocyclic ring opening of cis-bicyclo[m.n.0]alkenes: the anti-Woodward-Hoffmann quest

The dubbed anti-Woodward-Hoffmann ring-opening reaction of cis-bicyclo[4.2.0]oct-7-ene to yield cis,cis-cycloocta-1,3-diene has been intensively studied with robust, high-level computational methods. This reaction has been found to proceed through a conrotatory allowed pathway to afford cis,trans-cycloocta-1,3-diene followed by E to Z isomerization, instead of a disrotatory forbidden pathway, as suggested. Computational calculations of kinetic isotope effects are consistent with this interpretation and the experimental values. The study of lower bicyclic homologues with [3.2.0], [2.2.0] and [2.1.0] skeletons indicates the feasibility of a mechanistic change towards the anti-Woodward-Hoffmann disrotatory path. This is clearly favored for the ring opening of the highly strained cis-bicyclo[2.1.0]pent-2-ene and is highly competitive with the conrotatory path for cis-bicyclo[2.2.0]hex-2-ene. Therefore, the rearrangement of the smallest bicyclic cyclobutene is predicted computationally to be an anti-Woodward-Hoffmann disrotatory electrocyclic ring-opening reaction.     

Analysis of mitochondrial DNA for authentication of meats from chamois (Rupicapra rupicapra), pyrenean ibex (Capra pyrenaica), and mouflon (Ovis ammon) by polymerase chain reaction-restriction fragment length polymorphism

The prevention of fraudulent labeling of game meat constitutes an important part of food regulatory control and quality assurance systems. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis based on mitochondrial deoxyribonucleic acid (DNA) was developed for authentication of meats from chamois (Rupicapra rupicapra), pyrenean ibex (Capra pyrenaica), and mouflon (Ovis ammon). Amplification and restriction site analysis of a DNA fragment about 720 base pairs (bp) from the mitochondrial 12S rRNA gene of all analyzed species permitted the selection of Msel and Apol endonucleases for meat speciation. The 12S rRNA restriction profiles obtained allowed the unequivocal identification of chamois, pyrenean ibex, and mouflon/sheep and their differentiation from meats of domestic species such as cattle, goat, and swine. The highly variable mitochondrial D-loop gene was also targeted to attempt discrimination between mouflon and sheep meats. A D-loop region (700-1000 bp) was amplified and sequenced in all game and domestic species analyzed, and a primer set was designed for the selective amplification of a 370 bp DNA fragment from mouflon and sheep. PCR-RFLP analysis with the selected Maell enzyme generated a single electrophoretic profile characteristic for sheep, whereas 3 different fragment patterns were obtained for mouflon meats. Consequently, the PCR-RFLP technique developed can be routinely applied in inspection programs in order to verify the correct labeling of game species.     

Mutual Information and Quantum Discord in Quantum State Discrimination with a Fixed Rate of Inconclusive Outcomes

We studied the mutual information and quantum discord that Alice and Bob share when Bob implements a discrimination with a fixed rate of inconclusive outcomes (FRIO) onto two pure non-orthogonal quantum states, generated with arbitrary a priori probabilities. FRIO discrimination interpolates between minimum error (ME) and unambiguous state discrimination (UD). ME and UD are well known discrimination protocols with several applications in quantum information theory. FRIO discrimination provides a more general framework where the discrimination process together with its applications can be studied. In this setting, we compared the performance of optimum probability of discrimination, mutual information, and quantum discord. We found that the accessible information is obtained when Bob implements the ME strategy. The most (least) efficient discrimination scheme is ME (UD), from the point of view of correlations that are lost in the initial state and remain in the final state, after Bob’s measurement.