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Low Level Detection
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Trace Detection of Benzene in a Hydrocarbon (click the picture for a high quality version) |
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| Trace Detection of Benzene in a Hydrocarbon (top) |
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| The spectral response from trace concentrations of benzene in isopropyl alcohol are displayed to the right, and the observed spectral responses were initially background corrected. A PI-200 spectrograph containing high performance lenses was used for the benzene monitroing. Lower detection limits, down to the 5 ppm range, could be easily obtained by using our high performance CCD, increasing laser power, or increasing the sample integration time. |  |
| The figure to the right displays the linear relationship between the benzene peak intensity and the benzene’s concentration in a hydrocarbon. The linear relationship has a correlation coefficient of 0.9987 |  |
| Trace Detection of Sulfate in a Aqueous Solution (top) |
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| The spectral response from trace concentrations of sulfate in an aqueous solution are displayed to the right, and the observed spectral responses were initially background corrected. A PI-200-L spectrograph containing high performance lenses was used for this study. |  |
| The figure to the right displays the linear relationship between the sulfate peak intensity and the sulfate’s concentration in an aqueous solution. The linear relationship has a correlation coefficient of 0.9934. |  |
| Sulfate monitoring stability measurements were also conducted on a PI-200-L-HP. The Laboratory High Performance instrument utilized a deep depleted CCD that has a higher quantum efficiency and a laser with ~ 3 ½ times more power when compared to the standard PI-200-L instrument. One can notice that the high performance system has an improved signal to noise ratio. |  |
| Comparisons between the actual and predicted sulfate concentrations in an aqueous solution are displayed on the right. The standard deviation from the (actual – predicted) concentrations was 0.82 ppm and the linear relationship had a correlation coefficient of 0.976. |  |
| Toluene added to Benzene (top) |
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| Spectra of benzene with incremental additions of toluene. The left y-axis shows the intensity of the 990 cm-1 peak. The right y-axis shows the intensity of the smaller benzene peaks including the toluene peak at 784 cm-1. The spectra were obtained with an Andor CCD camera. |  |
| Closeup view of the 784 cm-1 toluene peak and the adjacent benzene peak. The spectra were normalized to the intensity of the 830 cm-1 benzene peak also shown. |  |
| Closeup view of the 784 cm-1 toluene peak. The change in the peak intensity is easily seen. |  |
| Nitrate added to Aqueous Solution (top) |
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| Spectra of a nitrate peak in an aqueous solution. The change in the peak intensity is easily distinguishable. |  |
| Plot of the nitrate peak intensity showing the linear change with concentration of nitrate in the aqueous solution |  |