According to the European Union SANCO/12571/2013 guidelines (SANCO, 2013), the precursor (parent) ion and the two transitions (quantification and identification ions) should be present with a signal-to-noise (S/N) ratio greater than 3 (in the lowest calibration level this ratio should be higher than 6); and the ratio of the quantification/confirmation transitions in the sample and the previously injected standard should not differ by more than ±30%