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Development of a Novel Mass Spectrometric ... - Jacobs University

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Results and Discussion<br />

Another graphical compositional image is a typical plot <strong>of</strong> H/C ratio vs. DBE<br />

(degree <strong>of</strong> unsaturation). Figure 3-76 shows such a plot for a measured light<br />

shredder waste sample. The H/C ratio was calculated from the molecular formulas<br />

<strong>of</strong> the waste components whereas the DBE values were obtained from the Data<br />

analysis program <strong>of</strong> the Bruker s<strong>of</strong>tware. From the graph it can be noticed that the<br />

majority <strong>of</strong> compounds within the waste extract are those having a DBE range <strong>of</strong><br />

4-8. n-Alkanes, that are found in the chemical content <strong>of</strong> the waste sample, are<br />

aligned at H/C value <strong>of</strong> 2 and DBE <strong>of</strong> 0.5. The latter value <strong>of</strong> DBE for n-alkanes<br />

results from their ionisation as (M-1) + . The DBE values <strong>of</strong> all the analytes <strong>of</strong> the<br />

waste are not adjusted against ionisation. The rule that lower H/C ratio corresponds<br />

to higher DBE is demonstrated in this plot. Of course the graph reflects a<br />

preferential dehydrogenation process arising from the high number <strong>of</strong> unsaturated<br />

compounds.<br />

Other effects like treatment <strong>of</strong> shredder waste on a small scale reactor and<br />

weathering <strong>of</strong> deposited shredder waste were frequently tracked by Kendrick plots.<br />

Our Project partners studied the effect <strong>of</strong> hydrothermal and aeration conditions<br />

over the waste in a small scale reactor in terms <strong>of</strong> time. Table 3.8 shows examples<br />

<strong>of</strong> treated samples on small scale under different conditions. Using the developed<br />

methodology, the samples were extracted and analysed accordingly. For example<br />

comparison <strong>of</strong> two different waste samples was performed by overlapping their<br />

two Kendrick plots. Figure 3-77 shows the Kendrick plot for initial sample I2 and<br />

I3 (Initial untreated samples) which were cropped at different times. I2 and I3 well<br />

overlap in the m/z 200 to 500 but differ significantly in the range m/z 500 to 1000.<br />

This shows that although these samples are similarly treated and their sources are<br />

roughly the same, they still vary according to Kendrick plot. The Kendrick plot<br />

here proves to be a magnificent chemical display to detect differences among<br />

samples. After that each sample on separate was treated under certain conditions in<br />

a small scale reactor. For example I1 (Initial sample cropped on 14.12.2010) was<br />

treated in duplicate under defined conditions as shown in table 3.8. The treatment<br />

was probed by subjecting the initial samples to different conditions such as air<br />

101

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