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3.4. The Limit of Quantitation (LOQ) It is the lowest concentration of analyte that can be determined with an acceptable level of uncertainty according [http://www.selleckchem.com/products/jq1.html check details] to Eurachem guideline and it is usually the lowest point on the calibration curve which is 2?��g/kg. The analytes were considered to be quantitative when their abundance confirmation ion signal to noise is S/N �� 3 with an accurate quantitation of ��20% of their true value in the calibration standard. Sample residues that met all criteria but had S/N [https://en.wikipedia.org/wiki/E-64 E-64] being the most affected compounds where their recovery at lower level was 65 and 69%, respectively, and at the second level was 61 and 56%. No significant dispersion of results was observed for the other remaining PAHs and recovery did not differ substantially at the lowest and the highest concentrations. According to Commission Regulation (EC) number 1881/2006 and (EC) number 333/2007 [22, 23], the maximum level for the determination of PAHs in fish was 2?��g/kg wet weight and the recovery range of the methods used should be 50�C120%, indicating that the validated method complies with these criteria. Where RSDpooled can be calculated [21] as RSDpooled=RSD12n1?1+RSD22n2?1+?n1?1+n2?1+?. (1) RSD is the relative standard deviation, n is the number of samples, and the equation used to calculate the recovery is [24] Recovery%=CfCe��100, (2) where Cf is the found concentration and Ce is the expected concentration. Figures ?Figures2,2, ?,3,3, and ?and44 represent mean recovery and RSD% ranges; most of the PAHs recovery was between 70 and 120% with most [http://www.selleckchem.com/products/r428.html R428 nmr] of RSD less than 10%. Figure 2 Figure 3 Figure 4 The reported results provide evidence that the adapted QuEChERS method achieved for most of the PAHs gives good recoveries, repeatability, and reproducibility. 3.6. Method Uncertainty Calculation Using these equations the following was found. Relative standard uncertainty URec = 3.6% and U(Rec)=sn. (3) Combined uncertainty Uc is Uc=Up2+URec2+URef=6.2%. (4) U c is combined uncertainty. URec is the uncertainty due to recovery. URef is the uncertainty due to reference standard preparation. Up is the uncertainty due to precision experiments.