In this paper, a method for characterizing an industrially significant reac
tion using chemometrics, fiber-optic UV/visible spectroscopy and a single f
iber transmission probe is reported. Aliquots of the reaction mixture were
also taken at constant intervals for off-line HPLC analysis. HPLC peak area
s were used to develop multivariate calibrations for the real-time determin
ation of product and consumption of reactants. Composition profiles and pur
e component spectra of the reactant mixture, intermediate, and product were
estimated using automatic window factor analysis (WFA), a type of self-mod
eling curve resolution (SMCR), without the aid of referee methods of analys
is or standards. Window edges were automatically refined by a new iterative
process that uses a robust adaptive noise threshold in the stopping criter
ion. Strong evidence for the formation of a reactive intermediate was detec
ted and characterized by SMCR that could not be detected by HPLC. Eight rep
licate runs over a period of 3 months demonstrated that the SMCR results we
re reproducible. Robust smoothing of the SMCR profiles with locally weighte
d scatter plot smoothing (LOWESS) was used to construct control charts for
detecting upsets in the batch reaction caused by the introduction of small
amounts of water. Residuals (smooth-unsmoothed) outside control limits (3 x
MAD, median absolute deviation of residuals from pre-run batches) Even use
d to detect small, sudden process upsets. (C) 1999 Elsevier Science B.V. Al
l rights reserved.