3. Results and discussion
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.
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).
3.1. Matrix effect assessment
The response of the detector system to certain pesticides
may be affected by the presence of co-extractives from the
sample [2,21–23]. These matrix-effects may be observed as an
increase or decrease in response, compared with those produced
by solvent solutions of the analyte. The effect of the matrix
can be variable and unpredictable in the occurrence of measurable
effects. The matrix effect on the detectors (ECD and NPD
(10 mL of wine) samples at different levels with fungicides
working solutions. The spiked samples were allowed to equilibrate
for one hour before extraction to allow the spiked
solution to penetrate the test material. Replicated (n = 5) samples
were all run and the recovery values were calculated for
each.