Microtiterplate phosphate assay based on luminescence quenching of a terbium complex amenable to decay time detection

Abstract

We describe a terbium-ligand complex (TbL) for a microtiterplate assay for phosphate (P) in the 0.3–100 μmol L −1 range based on luminescence quenching. As the pH optimum is at neutral pH (7.4) the probe is quenched by both, primary (H 2PO 4 −) and secondary phosphate (HPO 4 2−). The LOD is 110 nmol L −1. A Stern–Volmer study revealed that quenching is mostly static. Due to the ms-decay time of TbL, the first luminescence lifetime assay for phosphate could also be developed. The lifetime-based calibration plot is linear between 0.5 and 5 μmol L −1 of P. The effect of various surfactants on assay performance and a study on interferents are presented. The probe was successfully applied to determination of P in commercial plant fertilizers and validated against the molybdenum blue test. The probe is the most sensitive lanthanide-based probe for phosphate.