All three compounds were easily separated in different polarity capacity columns (DB-608) and (BPX-5 or DB-5 ms) and were detected with all three gas chromatography detectors y Figs. 1 and 2 shows GC-NPD and GC-ECD, respectively, chromatograms of an untreated tomato or grape sample extract solution analyzed for the purpose of checking the absence of interference peak in the chromatographic area of interest and of a fortified control sample. Quantification was performed by the external standard procedure. In the studied ranges of concentration, from 0.025 to 10 mg/L for ECD and 0.25 to 10 mg/L for NPD, good detectors linearity was achieved for all compounds (with correlation coefficients R2 >0.9612) and for all the kind of standards solutions (Table 1).