(a) Plot the K emission intensity vs. the concentration of K, and the determine the linearity (coefficient of determination, R2) from the regression statistics. (b) Plot the ration of the K emission intensity to the Li intensity vs. the concentration of K, and compare the resulting the linearity (coefficient of determination, R2) to that in part (a), Why does the internal standard improve linearity? (c) Calculate the concentration of K in the unknown using the internal method?
(Internal standard) Potassium (K) can be determined by flame emission spectrometry using a lithium (Li) internal standard. The following data were obtained for standard solutions of KCl and an unknown containing a constant, known amount of LiCl as the internal standard. All the intensities were corrected for background by subtracting the intensity of a blank.
|
Conc. K (ppm) |
1.0 |
2.0 |
5.0 |
7.5 |
10.0 |
20.0 |
Unknown |
|
Intensity of K Emission |
10.0 |
15.3 |
34.7 |
65.2 |
95.8 |
110.2 |
47.3 |
|
Intensity of Li Emission |
10.0 |
7.5 |
6.8 |
8.5 |
10.0 |
5.8 |
9.1 |
(a) Plot the K emission intensity vs. the concentration of K, and the determine the linearity (coefficient of determination, R2) from the regression statistics.
(b) Plot the ration of the K emission intensity to the Li intensity vs. the concentration of K, and compare the resulting the linearity (coefficient of determination, R2) to that in part (a), Why does the internal standard improve linearity?
(c) Calculate the concentration of K in the unknown using the internal method?
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