Standardization of a multivariate calibration model applied to the determination of chromium in tanning sewage

A multivariate standardization procedure was used to extend the lifetime of a multivariate partial least squares (PLS) calibration model for determining chromium in tanning sewage. The Kennard/Stone algorithm was used to select the transfer samples and the F-test was used to decide whether slope/bias correction (SBC) or piecewise direct standardization (PDS) had to be applied. Special attention was paid to the transfer samples since the process can be invalidated if samples are selected which behave anomalously. The results of the F-test were extremely sensitive to heterogeneity in the transfer set. In these cases, it should be taken as an interpretation tool.