A 2-WAY PROCEDURE FOR BACKGROUND CORRECTION OF CHROMATOGRAPHIC SPECTROSCOPIC DATA BY CONGRUENCE ANALYSIS AND LEAST-SQUARES FIT OF THE ZERO-COMPONENT REGIONS - COMPARISON WITH DOUBLE-CENTERING
A new procedure for detecting and correcting for baseline offset/drift and spectral background in hyphenated chromatographic data is developed. The procedure consists of several distinct steps: first, the major principal components in the zero-component chromatographic regions are extracted before the appearance of the first eluting chemical constituent and after elution of the last chemical constituent in a peak cluster. Comparison of the loading patterns of the first principal component in the two zero-component regions by means of congruence analysis is. used to reveal the presence of a constant spectral background and/or systematic baseline offset or drift. If baseline drift is revealed, the baseline for the whole chromatogram is estimated by means of a least-squares fit of the data from the two zero-component regions with retention time as 'independent' variable. A background-corrected chromatogram is finally obtained by subtracting the estimated spectral background and the estimated baseline from the original data. The new procedure is conceptually similar to double-centering of the data. However, as shown in this work, double-centering destroys the positivity of the data and introduces an artifical 'chemical' rank that complicates the resolution of the data. The new method is tested and compared with double-centering using experimental multicomponent data.