The method was validated following the analytical performance
parameters established by the International Conference
of Harmonisation (CPMP/ICH/281/96) and the IUPAC validation
guidelines (21,22). According to that, the validation process
included the evaluation of linearity, accuracy, precision, and the
limits of detection (LOD) and quantification (LOQ). Clean sediment
material, collected from a non-polluted area and submitted
overnight to high temperatures (> 100°C), was used as a
blank matrix. Accuracy and precision (intra and inter batch)
were evaluated analysing three replicates of each QC samples
and using the CRM NIST. Precision was expressed in terms of
the relative standard deviation (RSD) of the replicate measurements.
Accuracy was estimated as the percentage of agreement
between the method results and the nominal amount of the
added compound. The blankmatrices of the sediments, fortified
at three QCs concentrations, allowed for the calculation of the
recovery and the effectiveness of the extraction step. These
values were obtained comparing the QCs concentrations, calculated
after the SPME procedure, with those of the equivalent
QCs prepared in acetone. The LODs and LOQs were determined
evaluating the signal/noise ratio (S/N = 3 for the LODs, and S/N
= 10 for the LOQs).