Minimal clean-up and rapid determination of polycyclic aromatic hydrocarbons in instant coffee

The essential aim of this work is the development of a simple, fast, quantitative and economic method for polycyclic aromatic hydrocarbons (PAHs) potentially generated by roasting coffee beans, which is the most important process in the coffee industry for the development of the characteristic flavour of the bean mix. The PAHs were chosen because they differed in the number of aromatic rings, had different polarity, have low residual limits, are commonly widespread in the environment and are generated by roasting. The key issue is whether or not the most polar PAHs, those with lower molecular weight or less rings, appear in the water extracts of ground roasted coffee beans, taking into account that those PAHs with lower molecular weight are those with higher volatality. The proposed analytical method is also broadly applicable to other roasted foods or their aqueous extracts. The method was evaluated by constructing calibration curves, measurement of recovery and precision, and the limits of detection. The method involves extraction with hexane, clean-up with a silica cartridge, concentration to dryness and injection of the acetonitrile solution of the residue for HPLC analysis with fluorescence detection. The method allowed to confirm or not the presence of the selected PAHs in instant coffees.