Lightweight Spherical Cellulose Aerogels With High Zr-MOF Loadings for the Facile Extraction of Benzodiazepines From Human Urine and Hair Samples

A facile dispersive micro-solid phase extraction (D-μ-SPE) method that uses spherical cellulose aerogels is proposed herein for the trace detection of seven benzodiazepines in biological samples. Zirconium metal–organic framework (MOF) particles were dispersed in the cellulose aerogels to improve the extraction efficiency. The prepared lightweight spherical aerogels (diameter of approximately 2 mm) were easily collected from the solution using a disposable dropper, overcoming the difficult recycling of powdered MOFs. The effect of the MOF loading (39, 56, and 66 wt%) and the organic ligand (terephthalic acid, 2-aminoterephthalic acid, and 4,4′-biphenyldicarboxylic acid) in the Zr-MOF on the extraction ability of the hybrid aerogels towards benzodiazepines was studied. The hybrid aerogel with a UiO-67 loading of 66% showed the best extraction performance primarily because of the enhanced surface area, pore volume, and π–π stacking interactions. Moreover, the UiO-67/cellulose aerogel spheres were mechanically stable and showed reusability for at least eight consecutive extraction cycles. The main factors affecting extraction, such as solution pH, extraction time, type and volume of desorption solvent, and desorption time, were also examined. Under the optimal conditions, the limits of detection ranged from 0.01 to 0.03 µg/L, and the limits of quantification ranged from 0.02 to 0.10 µg/L. The recoveries were 81.8%–104.2% for urine samples and 81.5%–99.5% for hair samples. The results suggest that the spherical aerogel-based D-μ-SPE is a simple and effective method for the quantification of benzodiazepines in biological samples.