Methods and apparatus determine analyte concentra- don in vivo and in vitro by the steady state determination of luminescence lifetime. A fluoro-phore that is quenched by the analyte is free to undergo Brownian rotation. The fluoro-phore (12) is irradiated with continuous linearly po- larized light (24). Emitted luminescence is resolved into vector components parallel and perpendicular to the plane of polarization of the excitation light (36, 38). A math- ematical function is employed which relates the lumines- cence anisotropy to quencher concentration. For analytes which do not quench excited staves, a known quantity of the analyte is conjugated to a quencher molecule or energy transfer acceptor, and a competition reaction is set up in which labelled and unlabelled analytes compete for sites on a labelled carrier molecule. An empirically determined mathematical function is employed which relates lumines- cence anisotropy at the carrier label emission band to ana- lyte concentration.
ANALYTE DETECTION FROM STEADY-STATE LUMINESCENCE LIFETIME