Development of a Sensitive Monoclonal Antibody-Based Enzyme-Linked Immunosorbent Assay for the Analysis of Paclobutrazol Residue in Wheat Kernel

An indirect competitive enzyme-linked immunosorbent assay (icELISA) was developed with monoclonal antibody (mAb) mAb6H73C9 recognizing the plant growth regulator paclobutrazol (PBZ). The icELISA had a half-maximum inhibition concentration (IC50) and working range of approximately 8.7 and 2.0–50.4 ng/mL, respectively. Average recoveries of PBZ in the wheat (Triticum aestivum) kernel samples were between 84.3 and 118.9% with relative standard deviations between 3.9 and 14.2%. As determined by the icELISA and further confirmed by liquid chromatography–electrospray ionization quadrupole Orbitrap mass spectrometry (LC–ESI-MS) analysis, the maximum residue concentration was about 0.07 mg/kg in the kernel samples, which indicated that PBZ could transfer from PBZ- treated seedlings to the kernel samples. The correlation coefficient (R2) between icELISA and LC–ESI-MS results was 0.979, which manifested that the developed icELISA was sensitive enough for monitoring PBZ residues in wheat kernels.