Calibration transfer in chemiluminescence analysis - Application to chromium determination by luminol-hydrogen peroxide reaction

Direct standardization (DS) and piecewise direct standardization (PDS) meth ods are applied to multivariate standardization of chemiluminescence signal s using PLS model as the calibration model. The linear concentration interval of the chemiluminescence determination wa s determined. This interval was located using univariate robust calibration by least median of squares (LMS) method. The linear calibration model was corroborated by conventional least-squares method. The standardization subset and window size were optimized by means of the p rediction residual error sum of squares. Several instrumental sources of va riability have been studied: the detection cell, instrument, batch versus f low injection (FI) modes, time and their possible combinations. This study shows the calibration transfer can be employed successfully. The proposed strategy was used in the chemiluminescence determination of Cr (III), Cr(VI) and total Cr in water samples by means of a calibration trans fer. The obtained results are in agreement with reference method values and known spiked amounts, and are independent of the standardization factors. (C) 2001 Elsevier Science B.V. All rights reserved.