The formation of antigenic polymers in aqueous solutions of -lactam antibiotics.

Samples from concentrated aqueous solutions of β-lactam antibiotics were examined by gel filtration. The eluates were monitored by ultraviolet (uv) absorption and by passive cutaneous anaphylaxis (PCA) in guinea-pigs sensitized with appropriate antiserum raised in rabbits. The appearance of uv absorbing material, giving a positive PCA reaction, in fractions from the high molecular weight regions of the eluates from gel filtration of aged solutions was taken as evidence of antigenic polymer formation.