A novel cryogenic modulator was constructed for comprehensive two-dimensional gas chromatography (GC x GC). The modulator is based on two-step cryogenic trapping with CO2 and thermal desorption with electric heating. The GC x GC system included a nonpolar first-dimension column and two semipolar second-dimension columns, one connected to a flame ionization detector and the other one to a electron capture detector. A Matlab-based program, which allowed determination of peak heights and volumes, was written for the data analysis. The GC x GC system was applied for the analysis of polyaromatic hydrocarbons and polychlorinated biphenyls. The functioning of the modulator and the quantitativity of the method were studied with both peak volumes and peak heights from a three-dimensional plot. The separate peak areas from the modulated chromatogram were calculated as a comparison. The quantitative results were compared with those obtained with the same system but without the thermal modulation. The method was found to be repeatable and linear with use of peak volumes as well as peak heights. There was also good agreement with the results obtained by integration of separate peak areas. The developed GC x GC method was applied to the analysis of a Soxhlet extract of a certified sediment sample. The results were compared with the certified values.

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Metacognitive awareness consists of two components, i.e. regulation of cognition and knowledge of cognition. In earlier studies self-evaluation is aligned as a sub-component of regulation of cognition. However, in this study we point out that self-evaluation does not actually regulate the ongoing or forthcoming process but it is a tool used to reflect both knowledge and regulation. This alignment is modelled to assess to what extend self-evaluation can be predicted by the other components of the metacognitive awareness. The model is tested empirically among vocational education students (N= 578) using the Metacognitive Awareness Inventory (MAI). The results of SEM concludes that the conditions and goals appointed by the learner predict the selection of contents and strategies towards self-evaluation of one’s own learning. In other words, by measuring planning or conditional knowledge we could predict other components of knowledge or regulation and, especially, self-evaluation. The findings of this study extensively confirm that planning and knowledge of conditions predict success through the learning process. The results encourage teachers to support students in improving their metacognitive awareness, i.e. expect them to set goals for their own learning.

Comprehensive two-dimensional gas chromatography utilising a semi-rotating cryogenic modulator was applied to the analysis of dietary milk derived fatty acids. Four column combinations were tested: two polar-nonpolar and two different nonpolarpolar column combinations. Best results were obtained with a nonpolar-polar column set, with narrow-bore (50 microm ID) Carbowax column as the second column. The GC x GC method clearly improved the separation efficiency of the fatty acids in comparison with one-dimensional GC analysis and proved to be suitable for the quantification of the analytes. The relative standard deviations (RSD) of the retention times in the first and second dimensions were on average 0.06% and 4.9%, respectively. The relative RSD for peak volumes was on average 2.9%.