Technical Note: Optimization of the Hollow Fiber Microextraction conditions for the Determination of Pesticides in Whole Blood by GC-MS

In forensic toxicology, the sample preparation procedure has been a crucial step in the analytical method development. The main objectives of the sample preparation include the extraction and pre-concentration of the analytes and removal of interfering species, such as endogenous compounds in the biological samples. In recent years, microextraction techniques have been generating interest due to their advantages, especially because the solvent volumes employed during the extraction are greatly reduced, contributing to the principles of green chemistry. In this work, a method based on hollow fiber microextraction (HFµE) and gas chromatography coupled to mass spectrometry (GC-MS) was evaluated for determination of pesticides (chlorpyrifos, chlorpyrifos methyl, diazinon, disulfoton, terbufos alachlor, ametryn, and atrazine) in postmortem whole blood samples. The extraction procedure was performed using polypropylene fibers as device and 1-octanol as extraction solvent. The fiber was immersed under magnetic stirring in the donor phase, which consisted of 500 microliters of whole blood and 7.5 milliliters of buffer solution. After the extraction time, the fiber was transferred to a vial containing an organic solvent and the analytes were desorbed by stirring. The extraction procedure was optimized. In the desorption step, desorption solvent, agitation mode, and time were evaluated. Multivariate optimization of pH, agitation speed, and salt addition were also performed, followed by univariate optimization of extraction time. After optimization, the extraction conditions that showed the best response were: pH adjustment to value 6, stirring at 600 rpm for 40 minutes without salt addition. For the desorption step, 1 minute of vortex agitation using ethyl acetate as the desorption solvent was defined as the optimal desorption condition. Under these conditions, the pesticides were successfully extracted from postmortem whole blood samples.