A four-way calibration strategy based on photo-reaction time-dependent excitation-emission fluorescence matrices. Simultaneous analysis of four quinolones in complex samples with highly overlapped signals.

With the aim of quantifying four veterinary quinolones in tissue samples, a new procedure for obtaining third-order data to build a four-way calibration strategy was developed. This approach was based on recording excitation-emission fluorescence matrices as a function of the quinolone photoreaction time. A simple lab-made photoreactor was employed to induce the photochemical process, introducing an additional mode to improve selectivity. A fast-scanning spectrofluorometer was used to collect excitation-emission matrices at regular intervals over the total reaction time of 10 min. To overcome severe spectral overlap and the presence of uncalibrated interferents in complex matrices, unfolding partial least-squares coupled to residual trilinearization (U-PLS/RTL) was the model of choice for analyzing the obtained data. To avoid scattering signals, the spectral data range was restricted during the chemometric analysis. Through this methodology, satisfactory recovery values between 83 % and 126 % were attained for all target analytes in tissue samples, in accordance with established guidelines. Limits of detection and quantification ranged from 4 to 15 μg kg-1, and from 12 to 50 μg kg-1, respectively. Moreover, relative errors of prediction (REP) were lower than 9 %. Ultimately, the proposed approach, in addition to representing an alternative way of generating higher-order data, facilitates the determination of quinolones in complex samples through a simplified extraction and clean-up protocol, reduced analysis time, and the use of instrumentation of moderate complexity.