Screening metal binding selectivities of macrocycle mixtures by HPLC--ESI-MS and postcolumn reactions

A rapid method for the screening of metal binding selectivities of host compounds in mixtures is presented. This method involves the separation of mixtures of hosts by HPLC, followed by postcolumn complexation with one or more metals, then analysis by mass spectrometry. The intensities of the host-guest complexes in the mass spectra correlate with the binding selectivities of the hosts. The method was applied to a series of lariat ethers that were synthesized as ion-selective reagents for ion-selective electrodes. The compounds most selective for Na+ vs Li+ and K+ were identified. Additionally, a mixture of substituted calixarenes was screened for alkali-metal-binding selectivity. These compounds were determined to be selective for Cs+ over Rb+, K+, and Na+.