Calibration of Analytical Instruments. Impact of Nonconstant Variance in Calibration Data
| Autor: | Ketkar Sn, Thomas J. Bzik |
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| Rok vydání: | 2000 |
| Předmět: | |
| Zdroj: | Analytical Chemistry. 72:4762-4765 |
| ISSN: | 1520-6882 0003-2700 |
| DOI: | 10.1021/ac000018s |
| Popis: | Failure to appropriately account for the nonconstant variance in the calibration data often leads to unreasonable estimates of calibration parameters. In this paper, we contrast the normal regression-based approach (ordinary least squares) as applied to trace metals data collected via inductively coupled plasma mass spectrometry with a modified least-squares approach which explicitly uses the variance of the calibration data (weighted least squares). The use of ordinary least squares, in the case where the variance of the calibration data is not constant, results in inaccurate assessment of the intercept. The impact of this is to provide inaccurate results, at low concentration values. This is precisely the region of the greatest interest. In contrast, the use of a weighted least-squares approach results in the accurate determination of the intercept, thus providing accurate results at low concentration values. Method detection limits can also be calculated based on the two regression approaches. The weig... |
| Databáze: | OpenAIRE |
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