Analysis of Endocrine Disruptor Pesticides in Adipose Tissue Using Gas Chromatography-Tandem Mass Spectrometry: Assessment of the Uncertainty of the Method

A multiresidue method based on extraction with organic solvents, cleanup by preparative liquid chromatography, and detection by gas chromatography (GC) using tandem mass spectrometry (MS/MS) mode is described for the determination of α- and β-endosulfan and three main metabolites (sulfate, ether, and lactone) in human adipose tissue samples. The analytical methodology is verified, and the values of some performance characteristics, such as linearity, limit of detection (LOD), limit of quantification (LOQ) limits, precision (intraday and interday), and accuracy (recovery) are calculated. The high efficiency of the cleanup step for the elimination of interference allows reaching detection limits at low micrograms per kilogram (parts per billion, ppb) concentration levels. In addition, an estimation of measurement uncertainty, using validation data, is presented for each target compound. The results show that the sources of largest uncertainty are those relative to the balance calibration, from the gravimetric step, and both the relative uncertainty associated with the recovery and the intermediate precision of the method.