Second-order tensorial calibration for kinetic spectrophotometric determination

Kinetic-diode array spectrophotometric detection, as well as other multichannel techniques when used in non-equilibrium conditions, constitute second-order instrumentation. The second-order response provided will be bilinear, under certain conditions even trilinear, thus allowing the use of the generalized rank annihilation method (GRAM) and the trilinear decomposition method (TLD). Both numerically simulated and experimental data were used to evaluate the performance of these calibration techniques. The conditions in which the ‘second-order advantage’ (the possibility of quantifying the analytes in the presence of unknown reactions or interferences) is preserved were investigated. The coupling reaction of diazotized sulfanil-amide with p-, o- and m-amino benzoic acid, and with orciprenaline, to give azodyes was monitored. Binary mixtures of these substrates with different values of the rate constant ratio, and with various degrees of spectral overlap, were resolved. The advantages and limitations of higher-order data analysis techniques such as GRAM and TLD for the treatment of second-order kinetic data are discussed.