Determination of tetracyclines in surface water by partial least squares using multivariate calibration transfer to correct the effect of solid phase preconcentration in photochemically induced fluorescence signals Original Research Article

This manuscript proposes an approach to determine three tetracyclines (tetracycline, oxytetracycline and chlortetracycline) in surface water by photochemically induced fluorescence (PIF) detection. Ternary mixtures of these tetracyclines have been simultaneously determined by application of a multivariate calibration partial least squares (PLS) method. This methodology was applied to their determination in water samples using solid phase pre-concentration (SPE) with Oasis HLB cartridges. A suppression of the PIF signal for the three tetracyclines was found using SPE, and piecewise direct standardization (PDS), direct standardization (DS) and orthogonal signal correction (OSC) were used to transfer spectra obtained after SPE to spectra registered in pure solvent. PDS performed better than DS and OCS and, therefore, it was chosen as standardization method to transfer spectra. The application of the standardization method allows the determination of the three tetracyclines at concentration levels between 3 and 10 μg l−1 in surface water samples using a training set built with standards prepared in solvent, without SPE step.