KALMAN FILTERING FOR DATA REDUCTION IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

In ICP-AES, the analyte signal is superimposed on a background signal. When separating these signals, essentially by manual or automated three-point background correction, there are many instances in which the data reduction falls, e.g., with noisy analyte signals, nonlinear background signals, large and heavily structured background, and spectral interference. On the basis of scans in a fast scanning mode, the Kalman filter approach yields in all cases more accurate and precise results. It does not use a search for peak position or specific background points and processes peak area instead of peak height. It attains, up to 2 orders of magnitude, lower detection limits in the sample solution, for real-world samples. The application of the filter results in 1-pm spectral resolution at 20-pm spectral bandwidth and reduces the need for line selection, high-resolution spectrometers, and chemical separation of analyte and matrix. The improved analytical results obtained with the Kalman filter are due to its capability of noise averaging, of multiple line analysis, and of elimination of the degradation of detection limit caused by line overlap. If line selection is needed, it is done quantitatively. The power of the fully automated approach is illustrated with several applications: the analysis of high-purity uranium and sludge reference material. In every respect, data reduction by Kalman filtering is superior to three-point background correction.