Solid phase extraction (SPE) is often used for enrichment and clean-up prior to analysis of dissolved organic matter (DOM) by electrospray ionization (ESI) coupled to ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). It is generally accepted that extraction by SPE is not quantitative with respect to carbon concentration. However, little information is available on the selectivity of different SPE sorbents and the resulting effect for the acquired DOM mass spectra. Freshwater samples were extracted by the widely used PPL, HLB and C18 sorbents and the molecular composition and size distribution of the DOM in the extracts and in the permeates was compared to the original sample. Dissolved organic carbon (DOC) recoveries ranged between 20% and 65% for the three tested SPE sorbents. Size-exclusion chromatography coupled to organic carbon detection (SEC-OCD) revealed that limited recovery by PPL and HLB was primarily due to incomplete elution of a fraction of apparent high molecular weight from the solid phase. In contrast, incomplete retention on the solid phase, mainly observed for the C18 cartridge, was attributed to a fraction of low molecular weight. The FT-ICR mass spectra of the original sample and the SPE extracts did not differ significantly in their molecular weight distribution, but they showed sorbent specific differences in the degree of oxygenation and saturation. We concluded that the selective enrichment of freshwater DOM by SPE is less critical for subsequent FT-ICR MS analysis, because those fractions that are not sufficiently recovered have comparatively small effects on the mass spectra. This was confirmed by the extraction of model compounds, showing that very polar and small molecules are poorly extracted, but also have a low response in ESI-MS. Of the three tested SPE cartridges the PPL material offered the best properties for DOM enrichment for subsequent FT-ICR MS analysis as it minimizes too strong and too weak DOM-sorbent interactions.

The synergistic role of platinum and silica as a way to increase the final residue of pyrolized silicone was investigated and explained, giving new interpretations. Conditions were first set to study the thermal degradation of silicones in the presence of platinum based on the simplest silicone/silica/platinum formulation. Numerous parameters, e.g., platinum and silica content or silica surface modifications, were varied to track their influences on the final residues. A thorough DSC study, together with SEM/EDX and Pyrolysis/GC-MS analyses, led us to propose a three-stage process. The key parameter governing thermal stability and final content of the residue is the conjugated actions of immobilizing/cross-linking PDMS chains. Silica particles tether silicone chains through physical interactions, i.e., hydrogen bonding, facilitating a platinum radically catalyzed cross-linking reaction. Practical implications and possible improvements on LSR formulations are finally given.

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The present study aimed to investigate if growth conditions have an impact on the isomeric composition of lycopene in tomatoes. First a model system for photoinduced isomerization was established. Tomato extracts were irradiated with a halogen lamp, whose wavelength spectrum is close to the spectrum of daylight and thus mimics field-grown cultivation. Different optical filters were interposed between lamp and samples to simulate greenhouse conditions. 5-cis-Lycopene was formed preferentially while the concentration of 7-cis-lycopene decreased in field-grown model systems. The change of isomerization in greenhouse model systems led to a significantly different ratio. Consequently 5-cis- and 7-cis-lycopene were identified as potent markers for the differentiation of various lighting conditions during cultivation. This result was verified in biological samples. Authentic field-grown tomatoes (var. Lycopersicon esculentum Mill. var. commune L. H. Bailey "Harzfeuer") showed a significantly higher content of 5-cis-lycopene 5.90 ± 0.45% compared to tomatoes of the same variety grown under electric lighting 4.11 ± 0.10%. Additionally, the ratio of 7-cis-lycopene was significantly lower under field-grown conditions.