Ultrasensitive Detection of Phenolphthalein in Slimming Products by Gold-Based Immunochromatographic Paper

An anti-phenolphthalein monoclonal antibody (mAb) was prepared based on the N' N-carbonyldiimidazole (CDI) method through phenolphthalein conjugated with proteins. Indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and colloidal gold-based immunochromatographic assay (ICA) methods were used to determine phenolphthalein in slimming products. A standard curve was established, and the IC50 and limit of detection of ic-ELISA were 0.95 and 0.10 ng/mL with a linear detection range of 0.27-3.37 ng/mL. The developed ICA was used to detect phenolphthalein in tablets, capsules, and slimming tea samples with visual limit of detection values of 10 ng/mL, and cut-off values of 200 ng/mL. The results indicated that these two methods could be used to quickly detect phenolphthalein in slimming products.