Capillary electrophoresis–inductively coupled plasma-mass spectrometry hyphenation for the determination at the nanogram scale of metal affinities and binding constants of phosphorylated ligands

A screening strategy based on hyphenated capillary electrophoresis and inductively coupled plasma mass spectrometry (CE–ICP-MS) was developed to classify phosphorylated ligands according to their europium(III) binding affinity in a hydro-organic medium (sodium formate, pH 3.7, H2O/MeOH 90:10, v/v). Taking advantage of the high sensibility of ICP-MS for detecting phosphorus, this method enabled to assess the affinity of a variety of phosphorylated compounds, including phosphine oxides, thiophosphines, phosphonates, and phosphinates, in less than 1 h and using less than 5 ng of substance. By varying the total europium concentration, complexation constants could be determined according to a sequential multiple run strategy, which proved to be in excellent agreement with the values obtained by UV–Vis absorption spectrophotometric titrations.

► Fast screening strategy based on hyphenated capillary electrophoresis and ICP-MS.
► Assessment of equilibrium constants ascertained by spectrophotometric titration.
► 31P detection permitting studies of phosphorylated ligands, even UV-transparent ones.
► Application at low levels (5–20 ng).