On-line preconcentration of some rare earth elements in water samples using C18-cartridge modified with l-(2-pyridylazo) 2-naphtol (PAN) prior to simultaneous determination by inductively coupled plasma optical emission spectrometry (ICP-OES)

The on-line column preconcentration technique with inductively coupled plasma optical emission spectroscopy (ICP-OES) has been developed using a cartridge filled with octadecyl silica modified by l-(2-pyridylazo) 2-naphtol (PAN). The aim of this method was to determine some rare earth elements (REEs) (Ce, Dy, La, Sm, and Y) and uranium in water samples. Sample solutions were passed through the C18-modified column. The adsorbed cations were subsequently eluted from the column and transferred into the plasma with nitric acid solution for simultaneous determination of them. Sample pH, amount of PAN as a complexing agent, sampling and eluting flowrates and concentration of the eluent were optimized. Detection limits based on three times of standard deviations of blank by 10 replicates were in the range of 11 ng l−1 for Dy to 69 ng l−1 for U. Sample throughput was 10 samples h−1. The proposed method was applied to determine REEs in natural water samples. Recoveries of the REEs from natural water samples were between 95 and 106% with percent relative standard deviation (%R.S.D.) of 1.0-7.9%.