An evaluation of three commercially prepared anion-exchange resin columns for separation of tetraiodothryonine in serum.
Three different commercially prepared anion-exchange resin columns for thyroxine (T4) separation from serum for the "T4 by column" assay were evaluated using the protocol of the supplier. The claims by the suppliers for the distribution and recovery of T4 in the first and second thyroxine-containing eluates were experimentally evaluated by the addition of a tracer quantity of purified [125I]T4. The average experimentally determined elution ratios of recoverable T4 (sum of T4 in first and second eluates) with these commercial columns were: Bio-Rad, 92.2:7.8 (90:10 claimed); Oxford, 87.8:12.2 (94:6 claimed); and Curtis Nuclear, 88.7:11.3 (80:20 claimed). The percent recoveries of T4 in the first thyroxine-containing eluate were: Oxford, 82.3 + 9.70 (x +/- 1 S.D.); Bio-Rad, 91.75 +/- 2.09; and Curtis Nuclear, 74.20 +/- 6.14. Mean serum T4 values obtained by the column method with all commercial columns tested were lower than competitive protein binding radio-assay (CPBR) values if the former values were not corrected for recovery. When individual recovery correction factors were applied to column results, improved correlation and better correspondence of "T4 by column" mean values with the CPBR values were noted. It is concluded that the largest part of the total variability of the "T4 by column" assay is contributed by the chromatographic step when the colorimetric step is performed with an automated technique.
D000837:Anion Exchange Resins; D002852:Chromatography, Ion Exchange / Q000379:methods; D005069:Evaluation Studies as Topic; D006801:Humans; D011786:Quality Control; D013974:Thyroxine / Q000097:blood*
D000837:Anion Exchange Resins; D013974:Thyroxine