Comparison of new approach of GC-HRMS (Q-Orbitrap) to GC-MS/MS (triple-quadrupole) in analyzing the pesticide residues and contaminants in complex food matrices.

Performances of multiresidue analysis of one hundred of pesticides and contaminants, using GC-Q-Orbitrap method in full scan mode were compared to those obtained with GC-triple-quadrupole method in multiple reaction monitoring mode. In terms of sensitivity, 86% of molecules exhibited lower limit of detection values using GC-Q-Orbitrap than using GC-triple-quadrupole. For the GC-Q-Orbitrap method, more than 85% of the pesticides and contaminants showed good recovery [70-120%] in wheat samples, with relative standard deviation values < 20%. GC-Q-Orbitrap method appeared the most sensitive for most pesticides studied in wheat with limit of quantification values ranged between 0.1 µg/kg and 4 µg/kg. Moreover, the matrix effect was acceptable in wheat extracts for 84 molecules but strong suppression of the chromatographic signal was observed for 16 molecules for the GC-Q-Orbitrap method. The injection of unpurified wheat extracts spiked at 10 µg/kg proved the potential of the GC-Q-Orbitrap method for use in performing high-throughput pesticide screening.

Development of two-dimensional gas chromatography (GC×GC) coupled with Orbitrap-technology-based mass spectrometry: Interest in the identification of biofuel composition.

Comprehensive gas chromatography (GC) has emerged in recent years as the technique of choice for the analysis of volatile and semivolatile compounds in complex matrices. Coupling it with high-resolution mass spectrometry (MS) makes a powerful tool for identification and quantification of organic compounds. The results obtained in this study showed a significant improvement by using GC×GC-EI-MS in comparison with GC-EI-MS; the separation of chromatogram peaks was highly improved, which facilitated detection and identification. However, the limitation of Orbitrap mass analyzer compared with time-of-flight analyzer is the data acquisition rate; the frequency average was about 25 Hz at a mass resolving power of 15.000, which is barely sufficient for the proper reconstruction of the narrowest chromatographic peaks. On the other hand, the different spectra obtained in this study showed an average mass accuracy of about 1 ppm. Within this average mass accuracy, some reasonable elemental compositions can be proposed and combined with characteristic fragment ions, and the molecules can be identified with precision. At a mass resolving power of 7.500, the scan rate reaches 43 Hz and the GC×GC-MS peaks can be represented by more than 10 data points, which should be sufficient for quantification. The GC×GC-MS was also applied to analyze a cellulose bio-oil sample. Following this, a highly resolved chromatogram was obtained, allowing EI mass spectra containing molecular and fragment ions of many distinct molecules present in the sample to be identified.

N,N'-Dimethyl-ethylenediammonium dioxalatocuprate(II).

The asymmetric unit of the title salt, (C(4)H(14)N(2))[Cu(C(2)O(4))(2)], consists of one complex anion and two cationic half-mol-ecules, the other halves being generated by inversion symmetry. The Cu(II) atom in the anion is coordinated by two bidentate oxalate ligands in a distorted square-planar geometry. Inter-molecular hydrogen bonds, involving the NH groups as donors and O atoms as acceptors, are observed, which lead to the formation of a three-dimensional network structure.