Multi-element trace analysis by reversed-phase high-performance liquid chromatography followed by on-line column enrichment as 2-(5-nitro-2-pyridylazo)-5-[N-propyl-N-(3-sulphopropyl)amino] phenol chelates

Abstract

This paper reports the utilization of 2-(5-nitro-2-pyridylazo)-5-[N-propyl-N-sulphopropyl)amino phenol (Nitro-PAPS) as a chelating reagent using an ODS column for the preconcentration and the separation of metal ions by reversed-phase high-performance liquid chromatography (RP-HPLC) with ultraviolet-visible detection of 570 nm. Nitro-PAPS chelates were eluted within 12 min with tetrahydrofuran-acetonitrile-water (15:10:75, v/v) containing a 0.01 mol dm −3 phosphate buffer solution (pH 6.0) and 2·10 −7 mol dm −3 Nitro-PAPS as the mobile phase. When the Nitro-PAPS chelates were injected into the RP-HPLC system, they were retained on top of the column and did not travel in the column, with water as the sample solvent. The retained metal chelates were then allowed to travel in the column encountering the stream of the mobile phase. The separation of the peaks to chromatogram for each component was satisfactory. The determination limits (5σ) were 0.2 ng cm −3 for copper and iron, 0.04 ng cm −3 for nickel and 0.01 ng cm −3 for cobalt. The proposed method was applied to the determination of these metal ions in actual samples, such as rain and river water.