Multivariate calibration applied to a highly interfering chemical system -The simultaneous spectrophotometric determination of aluminium and iron inplants using xylenol orange and partial least-squares regression

A partial least squares (PLS) calibration model was developed for the simul taneous spectrophotometric determination of Al and Fe in plant extracts by using an excess of xylenol orange as the cromogenic reagent. Experimental c onditions were established to reduce interferences, decrease system complex ity and produce a robust procedure that could be used for routine analysis. The spectra should be recorded from 2 to 4h after mixing the reagents. Eth anolic solutions were used to improve the formation of the Al-XO complexes. The best calibration model was obtained using the PLS-2 algorithm after me an centering the data with five latent variables. Under the experimental co nditions adopted, only Zn was found to be a potential interfering species w ith the plant extracts used. Validation of the proposed spectrophotometric method was performed by running nine plant samples from the 1997 Internatio nal Plant-Analytical Exchange (IPE) which were also analyzed by ICP-AES for further correlation. The proposed procedure showed to be useful for predic tion of Al and Fe values from 12.5 to 2500 mg kg(-1) in plant dry weight ba sis. (C) 2000 Elsevier Science B.V. All rights reserved.