A highly sensitive analytical method for metal-labelled amino acids by HPLC/ICP-MS

Abstract

A highly sensitive method for the determination of amino acids by inductively coupled plasma mass spectrometry (ICP-MS), after separation by high performance liquid chromatography, was developed. Amino acids in the presence of a 0.1 mol L⁻¹sodium tetraborate solution were derivatized with a six-coordinated complex of ruthenium, bis(2,2′-bipyridine)-4′-methyl-4-carboxybipyridine-ruthenium N-succinimidyl ester-bis(hexafluorophosphate), dissolved in dimethylformamide. The derivatives were stable and were remained associated during separation on an octadecyl reversed phase column with a linear gradient elution using 100 mmol L⁻¹sodium phosphate buffer and acetonitrile. Ten kinds of amino acids derivatized with the reagent were successfully separated from each other. The ruthenium in the derivative was detected by quadrupole-based ICP-MS, and the detection limit for the amino acids (signal-to-noise ratio of 3) was 5 fmol per injection.