Dual-label time-resolved fluoroimmunoassay as an advantageous approach for investigation of diethyl phthalate & dibutyl phthalate in surface water

Due to the extensive presence of phthalate esters (PAEs) in the environment, it is very important to develop highly efficient methods for determining their environmental concentrations and for risk assessment. In this study, europium (Eu3+) and samarium (Sm3+) were employed as fluorescent labels to develop a dual-labeled time-resolved fluoroimmunoassay (TRFIA) for the sensitive detection of diethyl phthalate (DEP) and dibutyl phthalate (DBP) in aquatic environments. Under optimum conditions, the half-maximal inhibition concentration (IC50) and limit of detection (LOD, IC10) of the TRFIA were 28.1 and 4.9 ng/mL for DEP, and 33.4 and 3.9 ng/mL for DBP, respectively. The cross-reactivities of the TRFIA between these two phthalates and with their analogues were negligible. The proposed method indicated satisfactory accuracy with recoveries of 78.30-120.13% for DEP and 78.58-113.07% for DBP, which were in good agreement with the gas chromatography tandem mass spectrometry analysis results of the same samples. Meanwhile, the results of the immunoassay were used to evaluate the presence and environmental risk of those pollutants in the inner rivers of Zhenjiang city. The concentrations of DEP and DBP ranged from non-detectable to 61.31 ng/mL and from non-detectable to 94.57 ng/mL, respectively. The results of the potential ecological risk assessment by the risk quotient method showed that there were some sampling points exceeding risk limits, and the total ecological risk of DBP was higher than that of DEP. (c) 2019 Elsevier B.V. All rights reserved.