LABELING OF ESTRADIOL AND TESTOSTERONE ALKYLOXIME DERIVATIVES WITH A EUROPIUM CHELATE FOR TIME-RESOLVED FLUOROIMMUNOASSAYS

O-Carboxymethyl-, O-(4-aminobutyl)-, and O-(6-aminohexyl)-oximes of 6- oxoestradiol and testosterone were labeled using a described general l abeling method with a europium chelate. A stable amide or thiourea bon d was formed between the europium label and carboxyl or amino derivati ve of the steroid, respectively. These labeled ''tracers'' were purifi ed and briefly tested in a competitive time-resolved fluoroimmunoassay using monoclonal antibodies raised against O-(carboxymethyloxime)-bov ine serum albumin derivatives of estradiol and testosterone. Only buff er-based standards were used in a model system for the testing. These studies indicate only minor functional differences while using these a ntibodies due to the length of the spacer arm, and a higher sensitivit y in the clinically relevant standard range was reached with the longe r spacers.