Oxygen and nitrogen-doped graphitic carbon-iron carbide mesoporous nanocomposite as an efficient and durable adsorbent for packed in tube solid- phase microextraction of benzodiazepines.

BACKGROUND

In in-tube solid-phase microextraction (IT-SPME), the characteristics of the adsorbent significantly affect selectivity, sensitivity, and precision. Adsorbent stability and reusability are also crucial for repeated extractions. Therefore, developing suitable adsorbents with enhanced adsorption capacity and stability is crucial. Porous carbons are highly efficient adsorbents due to their large surface area, stability, and easily modified structure, which enhances selectivity. Precursor selection plays a key role in carbon-based adsorbent synthesis, influencing carbonization efficiency, porosity, graphitization, and the introduction of functional groups. Graphitized porous carbon materials functionalized with polar groups ensure high adsorption efficiency for polar organic compounds and offer good durability.

RESULTS

An oxygen and nitrogen-doped mesoporous graphitic carbon-iron carbide nanocomposite was synthesized by pyrolysis of a composite of a Zn-based metal-organic framework and polypyrrole (PPY). Characterization studies revealed mesoporous particles smaller than 30 nm, with a BET surface area of 126.59 m2 g-1 and an average pore diameter of 2.42 nm. X-ray diffraction analysis identified both graphitic carbon and iron carbide phases in the material. Furthermore, Raman and FT-IR spectroscopy verified the presence of graphitic carbon incorporating acidic and basic functional groups. The synthesized composite was employed as an efficient adsorbent in IT-SPME of benzodiazepine (BZD) drugs, followed by their quantification using HPLC-UV. Under the optimized conditions, the proposed method exhibited a linear range of 0.05-100.0 μg L-1, with detection limits between 0.02 and 0.20 μg L-1 for the drugs. Additionally, the method showed high extraction recoveries ranging from 50.2 % to 91.1 %, along with impressive preconcentration factors between 627 and 1138.

SIGNIFICANCE: The synthesized adsorbent was effectively applied to quantify BZDs in real samples with satisfactory recoveries. Its mesoporous structure and functionalized graphitic framework ensured strong analyte interactions, high extraction efficiency, and durability. Incorporating the Zn-based MOF into the precursor had a significant role in iron carbide formation and further enhanced the composite's adsorption capacity for BZDs compared to the PPY pyrolysis product alone.