Taking into account the time for calibration and preincubation with the antibody, she estimates that sample results could be obtained in 20 to 40 minutes. To create this new assay, Dr. Blake adapted existing immunoassay technology. A sample is first taken from the contaminated site and placed in a solution containing a chelator. In this solution, the metal contaminant will be pulled away from any other organic molecules that may be present in the sample and will form a complex with the chelator. Dr. Blake uses either very high concentrations of chelators or special chelators that bind very tightly to the metal ion to make sure that the contaminant metal ion, if it is already bound to an organic, will prefer the chelator and form a complex with it.
Antibodies bind to the metal-chelator complex.
At this point, the solution contains antibodies bound to metal chelator complexes as well as free, unbound antibodies. The immobilized and soluble forms of the complex compete for the unbound antibodies. Therefore, in this competitive assay, the immobilized complex easily captures these free antibodies with unoccupied binding sites. A wash step then removes any antibody that has not bound to the insoluble metal-chelate complex. The amount of antibody bound to the solid phase is inversely proportional to the concentration of metal ion in the original environmental sample.