Microtiter plate assay for phosphate using a europium–tetracycline complex as a sensitive luminescent probe

Abstract

A new luminescent europium probe is presented for the determination of phosphate (P) in microtiter plate format. The assay is based on the quenching of the luminescence of the europium-tetracycline (EuTc) 1:1 complex by phosphate using a reagent concentration of 20.8 mol/L. The probe is excited at 400 nm and displays a large Stokes' shift of 210 nm. The emission maximum is located at 616 nm. The system works best at neutral pH 7 and is therefore suitable for phosphate determination in biological and biochemical systems. The linear range of the calibration plot is from 5 × 10 −6 mol/L to 7.5 × 10 −4 mol/L of phosphate, and the limit of detection is 3 mol/L.

Artificial Receptors for the Recognition of Phosphorylated Molecules

“…656 Duerkop and co-workers studied the effect of inorganic phosphate on the luminescence of the europium(III) tetracycline complex ( 597c) . 657 Quenching was observed to be linear with phosphate concentration over the range of 5 × 10 -6 - 7.50 × 10 -4 M at neutral pH. This signal was also subject to little interference by common cations and anions.…”

Sensitive Terbium Probes for Luminescent Determination of both Alkaline Phosphatase and Codeine Phosphate

“…Therefore, the changes of the luminescence intensity of this band are most often used for analytical applications with Tb 3+ complexes. The lifetimes (τ) of the complexes in Tris–HCl buffer at pH 8 are long, with 1.530 ± 0.006 ms for Tb 3+ −L 1 and 1.070 ± 0.003 ms for Tb 3+ −L 2 , compared with those found previously 15 . The lifetimes were calculated using the formula y = Ae (− t /τ) .…”

Luminescent Chemical and Physical Sensors Based on Lanthanide Complexes

“…EuTc in a 3:1 stoichiometry responds to phosphate by a strong fluorescence enhancement [44], whereas its luminescence in a 1:1 stoichiometry is quenched by phosphate [45] and also by nucleoside phosphates such as ATP, ADP, or GTP [46]. Both effects can be used to apply EuTc as a probe for the determination of the activities of alkaline phosphatase [45] and creatine kinase [46].…”

“…Both effects can be used to apply EuTc as a probe for the determination of the activities of alkaline phosphatase [45] and creatine kinase [46]. Furthermore, EuTc was reported to form complexes with citrate and other species of the citrate cycle in cellular metabolism in a 1:1:2 stoichiometry of Eu 3+ /Tc/citrate.…”