Abstract
A deuterated spin-labeled derivative of cortisol (F3-SLD) was prepared by coupling cortisol-3-(O-carboxymethyl) oxime with 4-amino-1-oxyl-2, 2, 6, 6-tetramethylpiperidine-d17 and used to improve the sensitivity of spin immunoassay (SIA) of cortisol. The linewidth of the high-field peak of F3-SLD was 1.4G at the modulation amplitude (Hm) of 1.6G, and that of the undeuterated spin-label was 1.9G at Hm=2.0G. When 200 μl of cortisol standards was used for the assay, the minimum detectable concentration of cortisol was reduced from 10 ng/200 μl to 2.5 ng/200 μl by the use of F3-SLD. Although the increase in the sensitivity of SIA is not yet sufficient, the use of deuterated spin-labels is considered to be useful for enhancing SIA sensitivity.
