Adsorption of fluoroquinolones on hollow Co3S4 polyhedron sulfidated from ZIF-67 and its application of dispersed solid phase extraction prior to HPLC-UV

Background

Developing pretreatment technique with new adsorbent is essential to improve the detection sensitivity of trace fluoroquinolones (FQs) in complex sample. Zeolite imidazole skeleton-67 (ZIF-67) has adsorbability for FQs, but its structure of rhombohedral dodecahedra may reduce the efficiency of mass transfer, and its application is limited by the instability and poor recyclability.

Results

A S-doped hollow Co₃S₄ polyhedron was prepared by sulfidation of ZIF-67 with thioacetamide and applied for disperse solid phase extraction (DSPE) of four FQs. SEM and TEM confirmed its hollow structure, the BET specific surface area was 40.17 m²/g and the maximum adsorption capacity was up to 53.42 mg/g. The adsorption kinetics and isotherm of FQs on the Co₃S₄ polyhedron were investigated. The adsorption process was a chemisorption reaction, which depends on electrostatic interaction, surface complexation, π-π interaction and hydrogen bonding. A DSPE-HPLC-UV method based on the hollow Co₃S₄ polyhedron was developed to determine trace FQs. The method has broad linear range with LODs of 0.10 - 0.15 μg/kg and LOQs of 0.30 - 0.50 μg/kg. The intra-batch and inter-batch RSDs were less than 10%. The recovery rate of FQs in honey samples was satisfactory.

Significance

The hollow Co₃S₄ polyhedron has high extraction efficiency for FQs because of the large cavities. Its maximum adsorption capacity was higher than some adsorbents and about 2 - 3 times than ZIF-67. It has better stability and repeatability. The DSPE-HPLC-UV method based on the hollow Co₃S₄ polyhedron has high sensitivity and is dependable for the determination of trace FQs in complex sample.