In-vial polycaprolactone thin film for sampling and microextraction of sexual hormones in environmental waters and...

The sustainability of sample treatments is a hot topic that can be addressed focusing on miniaturization of techniques and design of more efficient and sustainable sorbents. In such scenario, in-vial microextraction is increasingly reported as a reliable alternative to other solid-phase extraction setups, as integrates sampling, adsorption and desorption in a single device before instrumental analysis. Polymeric thin films have proven to be a versatile and efficient material for microextraction processes, but more attention has to be paid to the preparation steps both in terms of nature of polymer and possible co-extractant, and of solvents applied during the solubilization process.

An in vial-microextraction device for sex hormones was fabricated using as the extractant a thin film made of a biodegradable polymer (polycaprolactone, PCL) directly formed on the bottom wall of a glass vial. The greenness assessment of the film preparation results in the selection of an environmentally friendly solvent (methyl-tetrahydrofuran) for PCL solubilization. After evaluation of key parameters (contact time, desorption solvent and conditions), efficient adsorption-desorption cycle is completed in 30 min. High simplicity, low sample manipulation (two steps), quantitative adsorption and recovery (EE% > 70; R% > 60 for most analytes, respectively) determined by HPLC- MS/MS greatly improve sample throughput and the greenness of the method (0.66 by AGREEprep and 7.58 by SPMS). The method was successfully validated in actual water samples, showing low limits of detection (2-35 ng L^-1), satisfactory linearity (0.5-50 μg L^-1), and limited matrix effects (<10 % for river and <25 % for wastewater).

This polycaprolactone film proved to be a biodegradable and sustainable sorbent towards sex hormones. Its applicability in the in-vial thin film microextraction ensures the whole sample treatment in the same vial with high throughput, low energy and solvent consumption, keeping unchanged performance for multiple cycles. The method combines a green sample treatment with accurate detection and high sensitivity by HPLC-MS/MS, representing significant progress in miniaturized devices for environmental scope.