Calibration, calibration drift and specimen interaction in autoanalyser systems

The Use of Kalman Filtering and Correlation Techniques in Analytical Calibration Procedures

Different chemometric methods to improve calibrations are described. A Kalman filter is applied for processing and predicting slowly varying parameters of a linear calibration graph. The results are used for the evaluation of unknown samples, and for deciding whether to calibrate again or to analyze the next unknown sample. Another approach of the calibration problem, particularly in chromatography, is the use of correlation techniques. The noise reduction property of correlation chromatography is used to extend the calibration graph to very low concentrations. Furthermore, an experimental technique to determine a calibration curve and the unknown sample simultaneously under exactly the same conditions is described.

Calibration drift in the automated determination of calcium and magnesium by atomic absorption

Calibration drift was studied in the automated on-line determination of calcium and magnesium by atomic absorption over periods of up to four hours. Automatic correlation for drift improved the precision of results.

Drift correction--a comparative evaluation of some alternatives

Three drift correction methods are described. The results obtained from computer simulation of these methods and their application to raw data obtained from a survey of multichannel continuous-flow analysers are discussed, with particular reference to the effects of each method on analytical precision and accuracy, and on between-analyser variation. A geometrically derived method of drift correction was found to be the most satisfactory.