DIRECT MICROTITRE PLATE ENZYME-IMMUNOASSAY OF FOLIC-ACID WITHOUT HEATDENATURATION OF SERUM

A new and simple method for enzyme immunoassay of folic acid (FA) has been developed, which does not require extraction or heat denaturation of serum. FA-free serum for standards was prepared by a new immunosor bent technique as conventional methods were unsuccessful. The detectio n limit of the assay is 0.05 ng/ml. Intra- and interassay variabilitie s ranged between 5-13.3%. Analytical recoveries obtained after spiking with different amounts of FA ranged between 93-110%. We eliminated th e interference of endogenous folate binding protein - a major problem in direct FA assay by incubating serum samples (or standards) with FA- HRP conjugate in antibody coated plates at 50 degrees C. Comparison of our data with results obtained by microbiological assay and also by h eating samples in alkaline buffer showed good correlation.