to prepare a radioligand for ria pasi was conjugated to tyramine using dcc the product was purified by flash chromatography over silica gel and c 18 hplc radioiodinated in the presence of chloramine t and the monoiodinated product purified by hplc a typical sample may be from urine or blood the samples are diluted in phosphate buffered saline 5 fold or more and dried at 60 u00b0 c in a speed vac a 1 1 mixture of pyridine and acetic anhydride is added and the mixture incubated at room temperature overnight and dried on a speed vac at 45 u00b0 c alternatively the sample may be incubated with 1 sulphuric acid in acetic anhydride at 60 u00b0 c for 2 hours predrying before incubation is optional after treatment by either method the sample is taken up in 50 volumes of pbs or imidazole buffer to 1 ml of volume aliquots are then assayed by elisa or ria fig1 gives the assay standard curve for totally acetylated myoinositol and indicates a sensitivity of the order of 0 5 picomols ml fig2 gives the corresponding assay curve for chiroinositol showing that both immunoassays achieve similar sensitivities the results of an elisa performed with antibodies raised against dci are shown in fig3 note the high binding affinity for derivatives of dci and the very low cross reactivity with the derivatives of other isomers of inositol the results of an ria for myoinositol performed with the antibodies raised against myoinositol is shown in.