Abstract: In this study, a novel semi-quantitative method to determine sibutramine in food supplements was developed using fluorescent microspheres competitive immunochromatography coupled with naked eye reading. In the method, four antigen-coated test lines were set on the test strip, allowing decreasing concentration gradients of the labelled antibody left after reaction with the tested antigen to react with the coating antigen, so that immune reaction could be achieved with multi-scale sensitivity. The excitation light source was electric torch at 470 nm. The concentrations of Tween-20, labeled antibody and coating antigen, nitrocellulose (NC) membrane type and reaction time were optimized. Semi-quantitative analysis was performed by counting the number of colored test lines. Under the optimized reaction conditions, the sensitivity of the method was 0.05 μg/mL and the detection ranged from 0 to 9.00 μg/mL. This method took 15 minutes without the need for any special instrument, giving results consistent with those of high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). The newly developed method was a simple, reliable and rapid method, and could be used in the rapid screening of sibutramine in food supplements.

Key words: sibutramine; semiquantitative; fluorescent microspheres; immunochromatography; food supplements