spike in internal standard

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lucindakasama
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spike in internal standard

From 5000ppm chromium standard 1ml is added to a 5ml sample in a 100ml volumetric flask, to make up a 20xdilution of the sample, and expecting the chromium to be reading 1 or0.9. Initialy the chromium red fine on the first batch raging from 0.9 to 1, as more batches where run the chromium increased upto 103ppm. I cleaned the sample introduction system, but no improvement. What can be wrong