Highly sensitive dioxin immunoassay and its application to soil and biota samples

Tetrachlorodibenzo-p-dioxin (TCDD) is a well-known highly toxic compound that is present in nearly all components of the global ecosystem, including air, soil, sediment, fish and humans. Dioxin analysis is equipment intensive and expensive requiring low ppt or even ppq levels of detection. A simple, rapid, cost-effective method of analysis is desired to enable researchers to explore issues involving dioxin more quickly and to make more rational regulatory decisions. A sensitive immunoassay for TCDD has been developed in this laboratory. In the present study, this assay is further optimized using a new coating antigen system and validated with biota samples by HRGC-HRMS. The I₅₀ of current assay to 2,3,7-trichloro, 8-methyldibenzo-p-dioxin (TMDD), a surrogate standard for TCDD, is 36±6.0 ppt, and the lower detection limit (LDL) is 4 ppt in the buffer. A good agreement between immunoassay and GC/MS was achieved for fish and egg samples. To interface with the immunoassay, a rapid sample preparation method was developed for soil samples. Without any further cleanup, the soil extracts can be directly used in the ELISA with a detection limit at the low ppt level. It can be used as an on-site tool for environmental monitoring.