Green Ultrasound-Assisted QuEChERS Based on Bacterial Cellulose-Supported CNT/LDH Nanohybrids, Followed by Gas Chromatography–Isotope Ratio Mass Spectrometry: Application in Vanillin Authentication

Abstract

A hybrid of Cu–Cr layered double-hydroxide and multiwalled carbon nanotubes supported by bacterial cellulose was prepared using a facile method. The synthesized nanocomposite was characterized using FT-IR, X-ray diffraction, field emission-scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer–Emmett–Teller and Barrett–Joyner–Halenda techniques, with a specific surface area of 47.2294 m² g^–1 and a pore volume of 0.187977 cm³ g^–1. This nanocomposite was utilized as the adsorbent phase in ultrasonic-assisted QuEChERS for vanillin in food samples. The concentration and naturalness of vanillin were determined with GC-FID and GC–isotope ratio mass spectrometry, respectively. Optimization was performed on the type and volume of the desorption solvent (methanol, 300 μL), desorption time (20 min), adsorption time (30 min), adsorbent dosage (300 mg), sample pH (7.0), and ionic strength (1% w/v). The method was validated by evaluating the linear range (0.3–2000 μg L^–1 and r² = 0.9995), detection limit (0.1 μg L^–1), and enrichment factor (28.3). This study represents the first report on the preparation and application of this novel adsorbent for the analysis of vanillin in milk and cake powders, achieving normalized recoveries between 76 and 110% (RSD % = 0.3–14.8%). Additionally, the eco-friendliness of the procedure was assessed using the analytical eco-scale (68/100) and AGREE methods (0.55/1.00).