Modulation of the measuring range of a radioimmunoassay using an organic water two phase system

A commercially available radioimmunoassay (RIA) kit was used to study the effects of organic solvents on antigen-antibody interactions. The RIA analysis was carried out in aqueous-organic two phase systems. After exposure to hydrophobic organic solvents the antibodies retained full binding capacity, while less hydrophobic solvents caused partial inactivation of the antibodies. A practical analysis for digoxigenin in organic solvents was developed using the RIA kit with polyclonal antibodies against digoxin. The sensitivity was modulated four orders of magnitude by the choice of organic solvent. The main factor influencing the sensitivity was the partitioning of digoxigenin between the aqueous and the organic phases. The technique developed is promising for the analysis of a variety of antigens dissolved in organic solvents.