Multi-class determination of polycyclic aromatic hydrocarbons, pesticides and polychlorinated biphenyls in aquaculture samples by gas chromatography/tamdem mass spectrometry with atmospheric pressure chemical ionization

Abstract

The increasing demand of aquatic products during the last decade has accelerated the growth of aquaculture industry. However, the availability of marine feed ingredients is considered a limiting factor for the sustainability and profitability of this industry. For this reason, marine components in feeds have been replaced by vegetal ingredients. This change has led to the emergence or increased levels of organic pollutants like polycyclic aromatic hydrocarbons (PAHs) in feeds and fish. The analysis of PAHs has been traditionally performed by gas chromatography coupled to mass spectrometry with electron ionization (EI) source. However, in the last years the application of atmospheric pressure chemical ionization (APCI) in environmental analysis has led to a notable sensitivity and selectivity improvement in selected reaction monitoring (SRM) based methods. The improved performance of GC-APCI-MS/MS enables to reduce the matrix content in the final extract by simple dilution, minimizing the matrix effect and avoiding the need of using matrix-matched calibrations. In this work, a multi-class method for the determination of 24 PAHs, 15 pesticides and 7 polychlorinated biphenyl (PCB) congeners in 25 different matrices, including fish tissues, feeds and feed components, has been developed based on gas chromatography coupled to triple quadrupole tandem mass spectrometry with APCI source (GC-APCI-QqQ MS/MS). The sample procedure was a modification of the unbuffered QuEChERS method, using freezing as an additional clean-up and diluting 10 times the final extract. Matrix effect was evaluated by comparing the calibration graphs obtained with standards in solvent and in matrix after applying different dilution factors. A ten-fold dilution of the sample extract was selected, as the relative error between the slopes of calibration in solvent and calibration in matrix was acceptable for most analyte/matrix combinations. The developed method was evaluated at 0.05 and 0.5 mg·kg-1 spiking levels. Lower concentrations could not be tested because ¿blank¿ samples contained, in most cases, concentrations around or above 0.005 mg·kg-1 of several target analytes, mostly PAHs. Isotopically labeled internal standards were applied to correct for remaining matrix effects and for recoveries.