Supercritical fluid immunoextraction: a new approach for immunoassay automation

The formation of antigen–antibody immunocomplexes and their extraction into supercritical CO2 is proposed as a method for minimizing sample preparation and raising selectivity in the analysis of complex samples. To this end, a flow manifold including a commercially available supercritical fluid extractor is used. The extractor allows the continuous elution and turbidimetric monitoring of immunocomplexes formed and extracted in a thimble prior to retention in a solid-phase sorption trap. This assembly for synchronous immunoreaction–extraction–sorption/elution–detection was successfully used in the automatic determination of human immunoglobulin G in serum samples, using antibody human immunoglobulin G as reagent. The proposed method was validated against a standard clinical method implemented by an external laboratory and supported by a certified reference material.