Monolithic and hierarchically porous biochar/cellulose aerogel as adsorbent for microextraction in packed syringe towards trace sulfonamides in water samples prior to UPLC-MS/MS.

In this study, biochars with desirable adsorption capacity were prepared by calcination of herbal medicine residue, and the obtained biochars were loaded on cellulose aerogel through a green synthesis method. The monolithic biochar/cellulose aerogel hybrid was packed in the syringe and used as adsorbent for microextraction in packed syringe (MEPS). After introducing cellulose aerogel as the support, the loss of powdered biochars was avoided, and the entire extraction process can be achieved through simple operation of filtration due to the macroporous structure of cellulose aerogel. Coupled with UPLC-MS/MS, the established method was successfully applied to determine trace level of sulfonamides (SAs) in water samples. Extraction parameters such as pH of sample solution, adsorbent type, sample volume, elution solvent type and elution solvent volume were studied. Under the optimized parameters (pH of sample solution:7, adsorbent type: biochar/cellulose aerogel, sample volume: 20 mL, elution solvent: 0.3 mL methanol, the number of aspiration and dispense of sample solution, washing solvent and elution solvent: 3), desirable linearity correlation coefficient (r) in the range of 0.9951-0.9972 was achieved. The limit of detection varied from 0.00407 to 0.0104 ng/mL, and recovery ranging from 65.3 % to 102.4 % was obtained. The proposed method was demonstrated to be sensitive, accurate and easily operative, providing a convenient protocol for sample pretreatment.