Automatic generation of photochemically induced excitation-emission-kinetic four-way data for the highly selective determination of azinphos-methyl in fruit juices

An application of four-way multivariate calibration for the quantitation of azinphos-methyl (AZM) in fruits is presented. The known photochemically induced degradation of AZM into a highly fluorescent product was exploited for the generation of third-order data with quantitative purpose. The data generation consisted in the measurement of excitation-emission fluorescence matrices at different times after UV-light irradiation. For this purpose, a reactor was built connecting an external UV-light source through an optical fiber to the sample holder. The data were modelled with two algorithms, PARAFAC and U-PLS/RTL. The second-order advantage was exploited in the analysis of samples containing un-modelled components and an improvement in the analytical figures of merit was observed as long as the data dimensions were increased. The method was successfully applied to the quantitation of AZM in apple, pear and peach juice samples with and without spiked analyte. The limits of detection were of 3.6 μg L−1 in aqueous solution and 21-66 μg L−1 in fruit juice samples.