Sustainable headspace-in-needle microextraction analysis of phthalates using biomass-derived carbon-coated needles

Phthalates are used in various products as plasticizers and pose environmental and health risks owing to their endocrine disruption potential. The detection of phthalates requires appropriate sample preparation, such as adsorption-based extraction. This study explores the conversion of withered flowers into activated hydrochar through hydrothermal carbonization and subsequent activation to utilize it as an adsorbent in in-needle microextraction for phthalates. The process involved the hydrothermal carbonization of rose petals and stems; subsequently, activation was optimized by applying the Box-Behnken design and response surface methodology. The resulting activated hydrochar was applied as a coating on the interior of a needle via sol-gel polymerization to form a polydimethylsiloxane/activated hydrochar composite. The optimal conditions for hydrothermal carbonization and activation were identified as a reaction temperature of 210 °C for 18 h using 7.5 g of withered rose, followed by activation at 600 °C with a melamine-to-biomass ratio of 1 : 1 and a potassium hydroxide-to-biomass ratio of 5 : 1, with subsequent analysis via GC-MS. The synthesized adsorbent was characterized using various analytical techniques, including BET surface area analysis, FE-SEM, FT-IR spectroscopy, and TGA. This innovative in-needle microextraction approach optimized for headspace extraction demonstrated efficient phthalate extraction. The method's efficacy was validated through parameters such as the LOD, LOQ, linearity, and recovery, and the method can be considered a sustainable and effective sample preparation technique. This study shows that this method is easy to fabricate, convenient for storage, cost-effective, and can detect phthalates for advanced sample preparation.