Metal-organic frameworks-coated stainless-steel needles for solid-phase microextraction of phthalates.

Three MIL-53(Al, Cr, and Fe) MOFs were synthesized and evaluated for extracting phthalates. As the best adsorbent examined by batch extraction, MIL-53(Cr) was selected for the preparation of solid-phase microextraction (SPME) devices. For this purpose, MOF particles were supported with commercial silicone sealants and dispersed inside stainless-steel needles. This design provides enhanced protection since the adsorbent is attached to the inner wall of a stainless-steel holder. The SEM images confirmed that the adsorbent morphology was uniform and completely linked to the inner needle wall, and the MOF particles were in their original structure, indicating that the SPME needles were made properly. The performance of the prepared needles was optimized in terms of the extraction/releasing time and temperature, and the analyte concentrations. The recoveries ranged between 84.7% for bis(2-ethylhexyl) phthalate and 96.1% for diisopentyl phthalate after 30 min of the extraction. The good extraction efficiency was attributed to the high surface area of MOFs and the presence of various interactions, including hydrogen bonding, dipole–dipole interactions, π-π stacking, van der Waals forces, and pore matching between the analytes and the prepared MOF-based sorbent. The linear range was 0.10 − 1300 μg L−1, and the LODs varied between 0.04 and 0.10 μg L−1. Intraday and interday RSDs were ≤ 6.6% for all solutes using the same SPME needle, while the reproducibility of the needle construction (n = 3) was ≤ 14.1%. A single needle could be used for at least 70 extraction/desorption replicate cycles without a significant decrease in its extraction capacity. The developed MIL-53(Cr)-based SPME needles were primarily applied to the determination of phthalates in commercial bottled water packaged in PET, glass, or aluminum containers, with detected concentrations ranging from 0.14 to 5.61 μg L−1. The applicability and robustness of the method were further demonstrated through analysis of stream and sewage water, vehicle exhaust emissions, and perfume samples using both direct immersion and headspace sampling modes. Compared to previously reported SPME methods, the needles showed comparable LODs and recoveries but a wider linear range due to the larger adsorbent amount in longer extraction needles (45 mm vs. 10 mm). These results demonstrate the effective preparation and application of MOF-based SPME needles for phthalate analysis.