Protein-binding assay for cyclic AMP: possible interference by traces of trichloroacetate.

When cyclic AMP is to be extracted from animal and plant tissues a 5% trichloroacetic acid (TCA) solution is often used as the initial extraction medium. We have shown that traces of trichloroacetate remain in the extract even after multiple solvent extraction and this impurity can cause inflated estimates of cyclic AMP (cAMP) in the protein-binding assay. This will only occur when it is necessary to employ relatively large volumes of TCA (i.e., tissues containing low levels of cAMP). For such tissues we recommend the use of a thin layer chromatographic purification stage to separate cAMP from the trichloroacetate residue.