Cr(III)/Cr(VI) determination in waste water by ICP/AES with on-line HPLC (HHPN) sample introduction

Using hydraulic high-pressure nebulization (HHPN) for sample introduction, an on-line high-pressure flow system (HPLC system) becomes a functional component of the ICP spectrometer. By placing additionally an HPLC column between the sample valve and the high-pressure injection/nebulization nozzle, an improved species analysis is attained. An example is given by online separation and determination of Cr(III)/Cr(VI) in real waste water samples with ICP/AES. The detection limit of each Cr oxidation state is 4 mu g L-1 with an analysis cycle time of 5 min. In comparison to conventional coupling of HPLC and ICP spectrometry a considerably higher sensitivity is achieved. Using spiked samples the recovery of HHPN-ICP/AES was on an average better than 98% in contrast to only 79% for Cr(VI) determination with a UV photometric reference method. Due to chromatographic separation of Cr(VI) from matrix components and Cr (III), the technique no longer shows the typical spectral interferences caused by Ca (267.716 nm Cr line) and Fe (283.563 nm Cr line).