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Chemical Stability and Compatibility - Yittrium count not stable
In an analytical sequence on ICP OES we observed that the internal standard ratio is not stable and it gradually increases with progress in analytical sequence. So for example if I start sequence with Y count ratio as 1 gradually it increases to 1.04.
Suprisingly when a new sequence is created with fresh calibration again the Y count ratio comes back to its original value of 1.0.
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admin
Total posts: 529
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Thanks for the information. |
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Brian Alexander, PhD
Total posts: 18
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As your data are ratios, it's important to know exactly how the software is calcualting the Y count ratio. One approach would be for the software to compare the Y counts in a reference solution (often a blank or calibration standard) to the Y counts in the unknown (sample) solution. The data you present would be consistent with this approach, and would effectively represent instrument drift as the analytical run proceeds. A second internal standard approach is to normalize the counts for the element being measured to the Y counts in the same solution, i.e., the software divides the Ca counts (for example) in a given solution by the Y counts in the same solution. If you can determine how the software is calculating the Y count ratio, then it would be possible to diagnose the root cause of any trends you may be observing. |