DELFIA^® Yellow plates have a high protein binding capacity combined with exceptionally low fluorescence background. The lower background and, hence, increased sensitivity result from a UV-absorbing agent in the plastic material that prevents the excitation of the plastic. The properties of the yellow plate are especially beneficial in multi-analyte DELFIA^® assays where samarium or terbium is used as a second label alongside europium.

DELFIA® (dissociation-enhanced lanthanide fluorescence immunoassay) is a time-resolved fluorescence (TRF) intensity technology. Assays are designed to detect the presence of a compound or biomolecule using lanthanide chelate labeled reagents, separating unbound reagent using wash steps. DELFIA assays are flexible, compatible with a variety of plate readers, and, as this is a wash-based technology, compatible with most sample types. The technology is based on fluorescence of lanthanide chelates (Europium, Samarium, and Terbium). The fluorescence decay time of these lanthanide chelate labels is much longer than traditional fluorophores, allowing efficient use of temporal resolution for reduction of autofluorescent background. The large Stokes’ shift (difference between excitation and emission wavelengths) and the narrow emission peaks contribute to increasing signal-to-noise ratio. Sensitivity is further increased because of the dissociation-enhancement principle: the lanthanide chelate is dissociated and a new highly fluorescent chelate is formed into a protective micellar solution. DELFIA lanthanide chelates require this dissociation/enhancement step for fluorescence (induced by addition of DELFIA Enhancement solution, DELFIA Inducer, and DELFIA Enhancer as appropriate to the particular lanthanide chelate).