3. Your coworker is analyzing a NIST soil standard for Nickel by atomic spectros

Question

3. Your coworker is analyzing a NIST soil standard for Nickel by atomic spectroscopy and finds recovery to be 145.9%. After freaking out over the poor results, she adds a 10.0 ppb nickel spike to that sample and determines a 95.4% spike recovery. She repeats the analysis of both standard and spike with the same results. She prepares and analyzes a whole new set of calibration standards. Using the new calibration curve she analyzes standard and spike again. She still gets the same results. Totally perplexed, she comes to you for advice. What will you tell her? What type of problem does she have (be specific)? How can she solve the problem?

Explanation / Answer

3. The NIST soil sample analyzed above showed much greater value for nickel in the soil sample. The unusually high value obtained by absorption measurement is due to the fact that the instrument is not calibrated prior to taking the absorption measurements. The ideal procedure would be is to prepare a blank solution without the soil sample in it and take an absorption measurement of this blank solution. This value is subtracted from the absorption measurement of the soil sample and that of the spiked solution measurment to get accurate value for the soil sample.

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