Use of an open-tubular trapping column as phase-switching interface in on-line coupled reversed-phase liquid chromatography-capillary gas chromatography

The applicability of open-tubular traps for phase switching in coupled RPLC—GC was studied. The phase-switching process involves sorption of the analytes of interest from a methanol—water mobile phase into the stationary phase of an open-tubular column, removal of the aqueous phase by purging the trap with nitrogen and desorption of the analytes with hexane. Water elimination carried out in this manner appears to be highly efficient. In the sorption step the sampling flow-rate and the capacity factors of the analytes in the trap are critical parameters. Using a 2 m × 0.32 mm I.D. trap with a swollen 5-μm stationary phase at flow-rates not exceeding 100 μl/min, polycyclic aromatic hydrocarbons are trapped quantitatively from 300 μl of aqueous phases containing up to 65% (v/v) of methanol. For desorption 70–125 μl of hexane are needed. These volumes are easy to handle in solvent elimination carried out using a PTV injector prior to transfer of the analytes to a GC column

Modification and re-validation of the ethyl acetate-based multi-residue method for pesticides in produce

The ethyl acetate-based multi-residue method for determination of pesticide residues in produce has been modified for gas chromatographic (GC) analysis by implementation of dispersive solid-phase extraction (using primary–secondary amine and graphitized carbon black) and large-volume (20 μL) injection. The same extract, before clean-up and after a change of solvent, was also analyzed by liquid chromatography with tandem mass spectrometry (LC–MS–MS). All aspects related to sample preparation were re-assessed with regard to ease and speed of the analysis. The principle of the extraction procedure (solvent, salt) was not changed, to avoid the possibility invalidating data acquired over past decades. The modifications were made with techniques currently commonly applied in routine laboratories, GC–MS and LC–MS–MS, in mind. The modified method enables processing (from homogenization until final extracts for both GC and LC) of 30 samples per eight hours per person. Limits of quantification (LOQs) of 0.01 mg kg−1 were achieved with both GC–MS (full-scan acquisition, 10 mg matrix equivalent injected) and LC–MS–MS (2 mg injected) for most of the pesticides. Validation data for 341 pesticides and degradation products are presented. A compilation of analytical quality-control data for pesticides routinely analyzed by GC–MS (135 compounds) and LC–MS–MS (136 compounds) in over 100 different matrices, obtained over a period of 15 months, are also presented and discussed. At the 0.05 mg kg−1 level acceptable recoveries were obtained for 93% (GC–MS) and 92% (LC–MS–MS) of pesticide–matrix combinations

Collaborating for Innovation: the socialised management of knowledge

Although the importance of diverse knowledge is widely recognised for open innovation, there may be a gap in our understanding of the social processes that shape how collaborators engage in knowledge exchange. This social gap may be significant because of the powerful, but largely unexplained, role attributed to trust as a social artefact. Moreover, we see trust as a process and that different types of trust are involved in the collaborative process. Thus, this paper uses a qualitative methodology to capture the experiences of innovation collaborators. As explanation of the dynamic interplays of knowledge and trust, we offer a description of phases in the process. Our analysis finds that the relationship moves from transactional to social. The early phases are characterised by technical knowledge, but the later and mature phases are identified with knowledge of the person and by personal trust. The success of innovation is a result of relationships with augmented trust. We found that a fabric of trust is woven from the weft of professional knowledge and the warp of personal knowledge to support innovation. We propose that this developing of relationships might be conceived as becoming more open in the sense of sharing with one another. If so, we seem to have described and offered a social dimension of open innovation

Solvent elimination rate in temperature-programmed injections of large sample volumes in capillary gas chromatography

Temperature-programmed sample introduction is a very useful approach for the injection of large sample volumes in capillary gas chromatography and also holds promise for liquid chromatography-gas chromatography coupling. The optimization of a temperature- programmed injector for both these applications depends on numerous factors such as sample volume, liner design and temperature, speed of sample introduction and purge gas flow-rate. The maximum allowable speed of introduction of large sample volumes with simultaneous elimination of the solvent is determined by the solvent elimination rate. A theoretical model is proposed to predict an optimum combination of the speed of sample introduction, the initial liner temperature and the purge gas flow-rate. The validity of the model is discussed and evaluated. The solvent elimination rate is shown to depend on, amongst others, the vapour pressure of the solvent, and can be increased by an increase in the purge gas flow-rate and/or by a decrease in the inlet pressure. The observed cooling effect and the effect of the design of the liner on the solvent elimination rate are emphasized

Oznaczanie cholesterolu w tluszczu mlekowym metoda chromatografii gazowej

The GC-method for determination of triacylglycerol composition in milk fat was found applicable for quantitation of cholesterol in milk, cream and butter providing that dotriacontane internal standard was introduced to the sample prior the separation. The standard deviation of cholesterol content was 9.11 mg/100 g fat at the level of 200 mg/100 g fat. The average recovery of cholesterol from butter-isolated fat was 94.3% within the range of 75- 500 mg/100 g fat. Similar contents of cholesterol in milk (239.24±42.63 mg/100 g), cream (243.42±26.83 mg/100 g) and butter (245.24 ±33.73 mg/100 g) wer,: found. The highest variation in cholesterol determinations was stated for milk (1".81 %) and the least for cream (11.02%)

The content of cholesterol in butter depending on the season and production method

The seasonal variations in the cholesterol content in butter in relation to the fatty acid compositions were studied. No statistically significant differences in the cholesterol content depending on the season of the year were found. The differences in the cholesterol content in butter manufactured conventionally or continuously were also insignificant (p=0.05). The analysis of correlation showed statistically significant (p=0.05) dependence between the butter cholesterol content and iodine value (r=0.47), volatile fatty acids content (r=-0.38), and the C16:0/C18:0 ratio (r = 0.36).Przebadano sezonowe zmiany zawartości cholesterolu w maśle i ich związek ze zmianami składu tłuszczu mlekowego. Nie wykazano statystycznie istotnego zróżnicowania zawartości cholesterolu zależnie od okresu produkcji masła (tab. 1, 2). Nie wykazano też statystycznie istotnych różnic zawartości cholesterolu w maśle produkowanym metodą periodyczną i ciągłą (tab. 3). Przeprowadzona analiza korelacji (tab. 4, rys. 1, 2 i 3) wykazała statystycznie istotną zależność między zawartością cholesterolu w tłuszczu mlekowym a wartością liczby jodowej (r = 0,47), zawartością grupy lotnych kwasów tłuszczowych (r = -0,38) oraz ilorazem zawartości kwasów C16:0/C18:0 (r = 0,36)