A method for analyzing pet food without sample processing is described for rapid identification of melamine based on mass spectrometry (MS) using soft ionization by direct analysis in real time (DART) to provide accurate measurement of mass and isotope-peak intensities, in-source collisionally activated dissociation (CAD) fragmentation, and determination of active hydrogens. Usually, MS analyses based on other than electron ionization (EI) spectra can be suspect because of the limited amount of information provided by a single mass spectral peak (or very few peaks). In such cases, additional degrees of confirmation are desirable to increase confidence in the experimental results. Chromatographic retention time can provide a degree of confidence; however, this requires time and, in some cases, detailed sample processing. Currently, the United States Food and Drug Administration uses a gas chromatography-EI-MS technique for the determination of melamine in pet food that involves sample extraction and derivatization prior to a lengthy chromatographic separation. In the method described here, identification is also confirmed through a determination of the number of active hydrogen atoms in the analyte molecule achieved by hydrogen/deuterium (H/D) exchange by treatment with deuterium oxide (D2O) at the initial stage of analysis. Cross-correlation of these four experimental data provides an unambiguous identification of melamine in contaminated pet food without the need for any sample preparation or chromatography. Limits of detection and the validity of the H/D exchange method as a confirmatory technique are also presented.

A method is described for the rapid identification of biogenic, volatile organic compounds (VOCs) emitted by plants, including the analysis of the temperature dependence of those emissions. Direct analysis in real time (DART) enabled ionization of VOCs from stem and leaf of several eucalyptus species including E. cinerea, E. citriodora, E. nicholii and E. sideroxylon. Plant tissues were placed directly in the gap between the DART ionization source skimmer and the capillary inlet of the time-of-flight (TOF) mass spectrometer. Temperature-dependent emission of VOCs was achieved by adjusting the temperature of the helium gas into the DART ionization source at 50, 100, 200 and 300 degrees C, which enabled direct evaporation of compounds, up to the onset of pyrolysis of plant fibres (i.e. cellulose and lignin). Accurate mass measurements facilitated by TOF mass spectrometry provided elemental compositions for the VOCs. A wide range of compounds was detected from simple organic compounds (i.e. methanol and acetone) to a series of monoterpenes (i.e. pinene, camphene, cymene, eucalyptol) common to many plant species, as well as several less abundant sesquiterpenes and flavonoids (i.e. naringenin, spathulenol, eucalyptin) with antioxidant and antimicrobial properties. The leaf and stem tissues for all four eucalypt species showed similar compounds. The relative abundances of methanol and ethanol were greater in stem wood than in leaf tissue suggesting that DART could be used to investigate the tissue-specific transport and emissions of VOCs.