Reaction cell inductively coupled plasma mass spectrometry-based immunoassay using ferrocene tethered hydroxysuccinimide ester as label for the determination of 2,4-dichlorophenoxyacetic acid Original Research Article

The high sensitive dynamic reaction cell inductively coupled plasma mass spectrometry (DRC ICP-MS)-based immunoassay using ferrocene (Fc) tethered hydroxysuccinimide ester as label for the determination of 2,4-dichlorophenoxyacetic acid (2,4-D) was presented. Ferrocene tethered hydroxysuccinimide ester was directly or via horse radish peroxidase (HRP) as a bridge coupled to monoclonal antibody (mAb) of 2,4-D. Competitive immunoreactions were completed in microtiter plate and the signal of 56Fe in the bound ferrocene labeled conjugate was detected by DRC ICP-MS. The potentially interfering 40Ar16O+ at the iron mass m/z 56 was reduced in intensity significantly by using NH3 as the reaction gas. The optimization process of the immunoassay was greatly simplified in the aid of enzyme linked immunosorbent assay (ELISA) procedure. The 2,4-D was determined in the dynamic range of 0.1–1000 ng/ml and the detection limits of the assays using the two ferrocene labeled conjugates were found to be 0.044 and 0.055 ng/ml, respectively. The relative standard deviation for six measurements were within 5.5–15.3%.