Assay of picogram level isocarbophos residue on tangerines and oranges with luminol–albumin chemiluminescence system

A sensitive flow injection–chemiluminescence (FI–CL) method for the determination of isocarbophos (ICP) residue on tangerines and oranges was proposed. It was found that the CL intensity from luminol–albumin CL reaction could be obviously quenched in the presence of ICP and the decrease in CL intensity was proportional to the logarithm of ICP concentrations ranging from 1.0 to 1000 pmol L–1, giving the limit of detection of 0.3 pmol L–1 (3σ). The proposed procedure was successfully applied to the determination of ICP residue on tangerines and oranges with recoveries varying from 92.0 to 111.0% and RSDs less than 5.0%. The possible CL mechanism of luminol–albumin–ICP reaction was discussed, and ICP to albumin’s binding constant (KD = 1.00 × 106 L mol–1) and the number of binding sites (n = 1.00) were given by the homemade FI–CL model.