Pressurized liquid extraction followed by gas chromatography with atomic emission detection for the determination of fenbutatin oxide in soil samples

A novel method for the determination of the miticide bis[tris(2-methyl-2-phenylpropyl)tin] oxide, also known as fenbutatin oxide (FBTO), in agricultural soils is presented. Pressurized liquid extraction (PLE) followed by analyte derivatization and extraction into isooctane was the used sample preparation approach. Selective determination was achieved by gas chromatography with atomic emission detection (GC-AED). Influence of different parameters on the performance of the extraction process is thoroughly discussed; moreover, some relevant aspects related to derivatization, determination and quantification steps are also presented. As regards PLE, the type of solvent and the temperature were the most relevant variables. Under optimized conditions, acetone, without any acidic modifier, was employed as extractant at 80 °C. Cells were pressurized at 1500 psi, and 2 static cycles of 1 min each were applied. Acetone extracts (ca. 25 mL) were concentrated to 1 mL, derivatized with sodium tetraethyl borate (NaBEt4) and the FBTO derivative, resulting from cleavage of the Sn–O–Sn bond followed by ethylation of the hydroxyl fragments, extracted into isooctane and determined by GC-AED. Under final working conditions, the proposed method provided recoveries from 76 to 99% for spiked soil samples, a limit of quantification of 2 ng g−1 and an acceptable precision. Analysis of samples from vineyards sprayed with FBTO, confirmed the persistence of the miticide in soil for more than 1 year after being applied.