of them covered a range of four and approximately a third a range of three orders of magnitude in the solvent. Matrix-matching typically reduced the dynamic range by about one order of magnitude due to matrix effects, as the LOD of the xenobiotics and human estrogens in the matrix was generally lower. The accuracy in a solvent standard compared to the expected concentration at level 6 ranged in solvent between 83% and 123% with an average of 104% for xenobiotics including human estrogens and 81% and 119% with an average of 101% for endogenous metabolites (Table /Table ). Furthermore, the extraction recoveries were evaluated in spiked urine and plasma samples (Table /Table ). The median recovery of xenobiotics and human estrogens was 97% in urine and 103% in plasma, whereas for metabolites, these figures were determined to be 97% and 99%, respectively. Only 10% of the analytes in urine and 14% in plasma had a recovery below 80%. The recoveries were above 120% for about 1% of compounds in urine and 3% in plasma. Several analytes, especially endogenous metabolites, were already present in high quantities in the non-fortified urine and plasma. Hence the extraction recovery was not estimated for all compounds.