Abstract: Cyclosporine derivatives useful as detectable tracer compounds for the immunoassay determination of cyclosporine are disclosed. The cyclosporine derivatives comprise a detectable moiety coupled to the amino acid at the first position (MeBmt) in cyclosporine, the second position (Abu) in cyclosporine, the third position (Sar) in cyclosporine, the eighth position (D-Ala) in cyclosporine, or the tenth position (MeLeu) in cyclosporine. A preferred cyclosporine derivative comprises a fluorescent moiety coupled to the hydroxyl group of the amino acid at the first position in cyclosporine, and is especially useful for the fluorescent polarization immunoassay determination of cyclosporine. A fluorescent polarization immunoassay method and test kit are also disclosed.

Abstract: Cyclosporine derivatives useful as detectable tracer compounds for the immunoassay determination of cyclosporine are disclosed. The cyclosporine derivatives comprise a detectable moiety coupled to the amino acid at the first position (MeBmt) in cyclosporine, the second position (Abu) in cyclosporine, the third position (Sar) in cyclosporine, the eighth position (D-Ala) in cyclosporine, or the tenth position (MeLeu) in cyclosporine. A preferred cyclosporine derivative comprises a fluorescent moiety coupled to the hydroxyl group of the amino acid at the first position in cyclosporine, and is especially useful for the fluorescent polarization immunoassay deterimination of cyclosporine. A fluorescent polarization immunoassay method and test kit are also disclosed.

Abstract: A precipitation reagent for use in analytical systems for the determination of hydrophobic analytes in a biological test sample, particularly analytical systems employing specific binding proteins for such analytes. The precipitation reagent precipitates interfering proteins, hemoglobin, and other interfering substances from a biological test sample while, at the same, maintaining hydrophobic analytes in solution and minimizing the denaturation of specific binding proteins, such as, for example, antibodies, which may be present in an immunoassay system. The precipitation reagent comprises a zinc salt, a glycol, and a straight or branced alcohol from about 1 to 4 carbon atoms, and may optionally contain an acid. A preferred precipitation reagent comprises zinc sulfate, methanol and ethylene glycol, and is particularly useful in a fluorescent polarization immunoassay for the determination of hydrophobic analytes, especially cyclosporine.