Electron spin resonance spectroscopic detection in high-performance liquid chromatography: determination of metal complexes with radical-containing chelating reagents

Abstract

The possibilities of the application of electron spin resonance (ESR) spectroscopy as a method of detection in high-performance liquid chromatography (HPLC) are described. For this purpose a commercially available high-performance liquid chromatograph and an ESR spectrometer were combined; no special interface was required for connecting the two instruments. The conditions for measurement of the ESR signal under flow conditions were optimised. The applicability of HPLC with ESR spectroscopic detection was demonstrated by determining a number of metals in the form of their complexes with spin-labelled nitrosyl-containing chelating reagents. For the determination of mercury(II) as its complex with 2,2,5,5-tetramethyl-4-(thiobenzoylmethylidene)imidazolidine-1-oxyl a detection limit of 1 × 10^–5M can be achieved. The linear dynamic range covers more than two orders of magnitude and the relative standard deviation is 5%(5 × 10^–4M Hg). The method should find wide application owing to the differences in the nature of the ESR spectra of the complexes and the reagent.