2.7. Quality control
Recovery tests were carried out by addition of each pyrethroid to a thatch sample at concentrations of 16 ng/g dry weight (dw) and to a breast milk sample at concentrations of 100 ng/g lipid weight (lw) (Table 1). These samples were previously analyzed in order to determine pyrethroid presence before spiking. Five replicates were prepared for evaluation of the reproducibility of the method. Recovery values were higher than 77% in straw and ranged between 48 and 91% in breast milk with relative standard deviation values lower than 3–20% (n = 5; Table 1). Method detection limits (MLODs) defined as the minimum amount of analyte which produces a peak with a signal-to-noise ratio equal to 3 were determined for each single pyrethroid isomers by estimating the relative isomer abundance of the relative peak areas. They ranged between 0.10 to 75 pg/g dw and 3.1 to 1100 pg/g lw for straw and breast milk, respectively (Table 1). Limits of quantification, defined as the minimum amount of analyte that produces a peak with a signal-to noise ratio equal to 10, ranged between 0.33 and 230 pg/g and between 8.3 and 3600 pg/g lw for straw and breast milk, respectively.