Performance Assessment in Fingerprinting and Multi Component Quantitative NMR Analyses.

An interlaboratory comparison (ILC) was organized with the aim to set up quality control indicators suitable for multicomponent quantitative analysis by nuclear magnetic resonance (NMR) spectroscopy. A total of 36 NMR data sets (corresponding to 1260 NMR spectra) were produced by 30 participants using 34 NMR spectrometers. The calibration line method was chosen for the quantification of a five-component model mixture. Results show that quantitative NMR is a robust quantification tool and that 26 out of 36 data sets resulted in statistically equivalent calibration lines for all considered NMR signals. The performance of each laboratory was assessed by means of a new performance index (named Qp-score) which is related to the difference between the experimental and the consensus values of the slope of the calibration lines. Laboratories endowed with a Qp-score falling within the suitable acceptability range are qualified to produce NMR spectra that can be considered statistically equivalent in terms of relative intensities of the signals. In addition, the specific response of nuclei to the experimental excitation/relaxation conditions was addressed by means of the parameter named NR. NR is related to the difference between the theoretical and the consensus slopes of the calibration lines and is specific for each signal produced by a well-defined set of acquisition parameters.

Resin-Immobilized Palladium Nanoparticle Catalysts for Organic Reactions in Aqueous Media: Morphological Aspects.

An insight into the nano- and micro-structural morphology of a polymer supported Pd catalyst employed in different catalytic reactions under green conditions is reported. The pre-catalyst was obtained by copolymerization of the metal-containing monomer Pd(AAEMA)2 [AAEMA-=deprotonated form of 2-(acetoacetoxy) ethyl methacrylate] with ethyl methacrylate as co-monomer, and ethylene glycol dimethacrylate as cross-linker. This material was used in water for the Suzuki-Miyaura cross-coupling of aryl bromides, and for the reduction of nitroarenes and quinolines using NaBH4 or H2, as reductants. TEM analyses showed that in all cases the pristine Pd(II) species were reduced in situ to Pd(0), which formed metal nanoparticles (NPs, the real active species). The dependence of their average size (2-10 nm) and morphology on different parameters (temperature, reducing agent, presence of a phase transfer agent) is discussed. TEM and micro-IR analyses showed that the polymeric support retained its porosity and stability for several catalytic cycles in all reactions and Pd NPs did not aggregate after reuse. The metal nanoparticle distribution throughout the polymer matrix after several recycles provided precious information about the catalytic mechanism, which was truly heterogeneous in the hydrogenation reactions and of the so-called "release and catch" type in the Suzuki coupling.

Quality evaluation of table grapes during storage by using 1H NMR, LC-HRMS, MS-eNose and multivariate statistical analysis.

Three non-targeted methods, i.e. 1H NMR, LC-HRMS, and HS-SPME/MS-eNose, combined with chemometrics, were used to classify two table grape cultivars (Italia and Victoria) based on five quality levels (5, 4, 3, 2, 1). Grapes at marketable quality levels (5, 4, 3) were also discriminated from non-marketable quality levels (2 and 1). PCA-LDA and PLS-DA were applied, and results showed that, the MS-eNose provided the best results. Specifically, with the Italia table grapes, mean prediction abilities ranging from 87% to 88% and from 98% to 99% were obtained for discrimination amongst the five quality levels and of marketability/non-marketability, respectively. For the cultivar Victoria, mean predictive abilities higher than 99% were achieved for both classifications. Good models were also obtained for both cultivars using NMR and HRMS data, but only for classification by marketability. Satisfying models were further validated by MCCV. Finally, the compounds that contributed the most to the discriminations were identified.

A community-built calibration system: The case study of quantification of metabolites in grape juice by qNMR spectroscopy.

Nuclear Magnetic Resonance (NMR) is an analytical technique extensively used in almost every chemical laboratory for structural identification. This technique provides statistically equivalent signals in spite of using spectrometer with different hardware features and is successfully used for the traceability and quantification of analytes in food samples. Nevertheless, to date only a few internationally agreed guidelines have been reported on the use of NMR for quantitative analysis. The main goal of the present study is to provide a methodological pipeline to assess the reproducibility of NMR data produced for a given matrix by spectrometers from different manufacturers, with different magnetic field strengths, age and hardware configurations. The results have been analyzed through a sequence of chemometric tests to generate a community-built calibration system which was used to verify the performance of the spectrometers and the reproducibility of the predicted sample concentrations.

31P and 195Pt solid-state NMR and DFT studies on platinum(i) and platinum(ii) complexes.

31P and 195Pt solid state NMR spectra of anti-[(PHCy)ClPt(µ-PCy2)2Pt(PHCy)Cl] (3) and [(PHCy2)Pt(µ-PCy2)(κ2P,O-µ-POCy2)Pt(PHCy2)] (Pt-Pt) (4) were recorded under cross polarization/magic-angle spinning conditions (31P) or with the cross polarization/Carr-Purcell-Meiboom-Gill pulse sequence (195Pt) and compared to the data obtained by relativistic DFT calculations of 31P and 195Pt CS tensors and isotropic shielding at the ZORA spin-orbit level. A good agreement with the experimental results was found and it was possible to rationalize the chemical shift differences of 195Pt and 31P nuclei between compounds 3 and 4 as mostly due to a change (in opposite directions for 195Pt and 31P) of the principal component of the shielding tensor perpendicular to the molecular plane defined by the Pt and P atoms. Paramagnetic and spin-orbit terms were found to be the most important contributions to 195Pt and 31P shielding.

New "green" approaches to the synthesis of pyrazole derivatives.

A novel approach to the synthesis of pyrazole derivatives from tosylhydrazones of alpha,beta-unsaturated carbonyl compounds possessing a beta-hydrogen is proposed, exploiting microwave (MW) activation coupled with solvent free reaction conditions. The cycloaddition was studied on three ketones (trans-4-phenyl-3-buten-2-one, beta-ionone and trans-chalcone). The corresponding 3,5-disubstituted-1H-pyrazoles were obtained in high yields and after short reaction times. In order to simplify and point out the green chemistry features of the method, a further improvement was achieved under the same catalytic conditions with a "one pot" synthesis of these heterocyclic compounds, starting directly from their carbonyl precursors via tosylhydrazones generated in situ. For an exhaustive study, the dielectric properties of the solid reaction mixtures were also measured, in order to obtain input data for the numerical simulation of their heating behaviour in the single mode MW cavity which was used for experimental work. In order to supply a valid methodology and tool for measuring the environmental impact, a comparative study between the synthetic route proposed and the classical synthetic route has been carried out.

On the use of Ethephon as abscising agent in cv. Crimson Seedless table grape production: combination of Fruit Detachment Force, Fruit Drop and metabolomics.

The effect of 2-chloroethylphosphonic acid (Ethephon, in the following ETH) as abscising agent on cv. Crimson Seedless table grape was investigated by means of Fruit Detachment Force (FDF) and Fruit Drop (FD) analyses combined with a metabolomic study carried out by High Resolution Mass Spectrometry (HRMS) and Nuclear Magnetic Resonance (NMR) spectroscopy. The effectiveness of ETH as abscising agent was ascertained with ETH concentration ranging from 1.4 to 4.0 g/L in a two-year study. The ETH treatments caused berry drops higher than 40% and induced an increase of tartaric acid, procyanidin P2, terpenoid derivatives and peonidin-3-glucoside as well as a decrease of catechin and epicatechin. HRMS-NMR covariance analysis was carried out to correlate the fluctuations of tartaric acid NMR signals to those of MS peaks of the secondary metabolites affected by ETH treatments.

Reactivity of the phosphinito bridged Pt(I) complex [(PHCy2)Pt(µ-PCy2){κ2P,O-µ-P(O)Cy2}Pt(PHCy2)](Pt-Pt) towards Au(I) and Ag(I) electrophiles.

The reactivity of the phosphinito bridged Pt(I) complex [(PHCy(2))Pt(1)(µ-PCy(2)){κ(2)P,O-µ-P(O)Cy(2)}Pt(2)(PHCy(2))](Pt-Pt) (1) towards Au(I) and Ag(I) electrophiles was explored. Treatment of 1 with AuCl yielded the dichloro Pt(II) complex [(Cl)(PHCy(2))Pt(µ-PCy(2)){κ(2)P,O-µ-P(O)Cy(2)}Pt(Cl)(PHCy(2))] (4), while [Au(PPh(3))Cl] in thf (or toluene) caused ligand exchange resulting in the formation of [(PPh(3))Pt(µ-PCy(2)){κ(2)P,O-µ-P(O)Cy(2)}Pt(PHCy(2))](Pt-Pt) (7) and [(PPh(3))Pt(µ-PCy(2)){κ(2)P,O-µ-P(O)Cy(2)}Pt(PPh(3))](Pt-Pt) (8). With [Au(PPh(3))OTf] (independently from the solvent) or with [Au(PPh(3))Cl] (only in dichloromethane), reaction with 1 gave [(PHCy(2))Pt(1)(µ-PCy(2)){κ(2)P,O-µ-P(O)Cy(2)}Pt(2){µ-Au(PPh(3))}(PHCy(2))]X(Pt-Pt) ([6]X, X = OTf, Cl) clusters in which the [Au(PPh(3))] moiety bridges the µP-Pt(2) bond. The [Ag(PPh(3))](+) electrophile attacks complex 1 selectively at the Pt(2)-µP bond to afford, at low T, the cationic cluster [(PHCy(2))Pt(1)(µ-PCy(2)){κ(2)P,O-µ-P(O)Cy(2)}Pt(2){µ-Ag(PPh(3))}(PHCy(2))](+)(Pt-Pt) (10(+)) in which the [Ag(PPh(3))](+) moiety bridges the µP-Pt(2) bond. Clusters analogous to 10(+), but without PPh(3) bonded to Ag, are obtained from reactions of 1 with AgOTf, AgBF(4), AgClO(4) and AgCl.

A combined approach for characterisation of fresh and brined vine leaves by X-ray powder diffraction, NMR spectroscopy and direct infusion high resolution mass spectrometry.

X-ray powder diffraction was combined, for the first time, with Nuclear Magnetic Resonance spectroscopy and direct infusion mass spectrometry to characterise fresh and brined grape leaves. Covariance analysis of data generated by the three techniques was performed with the aim to correlate information deriving from the solid part with those obtained for soluble metabolites. The results obtained indicate that crystalline components can be correlated to the metabolites contained in the grape leaves, paving the way to the use of X-ray diffraction analysis for food fingerprinting purposes. Moreover it was ascertained that, differently from most of the metabolites present in the fresh vine leaves, linolenic acid (an omega-3-fatty acid) and quercetin-3-O-glucuronide (a polyphenol metabolite) do not undergo sensible degradation during the brining process, which is used as preservative method for the grape leaves.