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Quality assurance and statistical control

  • Heydorn, K.
Publication Date
Jan 01, 1991
Online Research Database In Technology
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In scientific research laboratories it is rarely possible to use quality assurance schemes, developed for large-scale analysis. Instead methods have been developed to control the quality of modest numbers of analytical results by relying on statistical control:<br/><br/>Analysis of precision serves to detect analytical errors by comparing the a priori precision of the analytical results with the actual variability observed among replicates or duplicates. The method relies on the chi-square distribution to detect excess variability and is quite sensitive even for 5-10 results.<br/><br/>Interference control serves to detect analytical bias by comparing results obtained by two different analytical methods, each relying on a different detection principle and therefore exhibiting different influence from matrix elements; only 5-10 sets of results are required to establish whether a regression line passes through the origo.<br/><br/>Calibration control is an essential link in the traceability of results. Only one or two samples of pure solid or aqueous standards with accurately known content need to be analyzed.<br/><br/>Verification is carried out by analyzing certified reference materials from BCR, NIST, or others; their limited accuracy of 5-10% make them less suitable for calibration purposes.

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