Authenticating Emergent Adulterant 6-Benzylaminopurine in Bean Sprouts: Virtual Hapten Similarity Enhanced Immunoassay

6-Benzylaminopurine (6-BA), a plantgrowth regulator with cytokinin-likeproperties, was recently reported to be illegally used in bean sproutsto increase their commercial appearance. It is still neverthelesschallenging to quickly detect this adulteration. In this work, fournovel haptens (haptens 1-4) of 6-BA were rationally designedwith computer-assisted modeling analysis and then synthesized foruse as immunizing haptens to produce antibodies. One of two obtainedantibodies showed high sensitivity and specificity toward 6-BA. Basedon the most sensitive anti-6-BA antibody, an indirect competitiveenzyme-linked immunosorbent assay (icELISA) was performed, which demonstrateda 50% inhibition concentration (IC50) of 1.18 mu g/Land a limit of detection of 0.075 mu g/L. The average recoveriesof this icELISA for 6-BA of spiked samples ranged from 87.2 to 95.0%with a coefficient of variation of less than 8.7%. Furthermore, theblind samples were detected simultaneously by the method and HPLC-MS/MS,and the results showed good agreement with each other. Therefore,the proposed icELISA can facilitate the rapid surveillance screeningof adulterated 6-BA in sprout vegetables.