Sensitive determination of mandelic acid in urine samples by D-μSPE using an H-ZSM-5@UiO-66 composite

A zeolite@metal-organic framework composite, H-ZSM-5@UiO-66, was synthesized and applied as a novel adsorbent for the rapid and sensitive dispersive micro-solid phase extraction (D-μSPE) of mandelic acid (MA) from human urine samples, followed by HPLC-UV analysis. The synthesized composite was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and field emission scanning electron microscopy (FE-SEM). The main experimental variables influencing the D-μSPE procedure were systematically investigated and optimized using a central composite design (CCD). Under the optimized conditions (sample volume: 8.5 mL; pH: 5.75; adsorbent mass: 35 mg; extraction time: 5 min; elution with water-methanol (5:5, v/v), 7 mL; desorption time: 5 min), the method exhibited high sensitivity, with limits of detection (LOD) and quantification (LOQ) of 0.04 and 0.09 μg mL^-1, respectively. Excellent extraction efficiency (93.8%), a wide linear dynamic range (0.30-120 μg mL^-1, R² > 0.9992), and satisfactory precision (RSD <3.9%) were achieved. The developed D-μSPE:H-ZSM-5@UiO-66-HPLC-UV method proved to be a reliable and effective approach for the determination of trace levels of MA in real urine samples.