Evaluation of on-line desalter-inductively coupled plasma-mass spectrometry system for determination of Cr(III), Cr(VI), and total chromium concentrations in natural water and urine samples

We have developed a simple and convenient method for the determination of Cr(III), Cr(VI), and the total chromium concentrations in natural water and urine samples that use a flow injection on-line desalter-inductively coupled plasma-mass spectrometry system. When using aqueous ammonium chloride (pH 8) as the stripping solution, the severe interference from sodium in the matrix can be eliminated prior to inductively coupled plasma-mass spectrometry measurement, and the Cr(VI) level can be determined directly. To determine the total concentration of Cr in natural water and urine samples, we used H2O2 or HNO3 to decompose the organic matter and convert all chromium species into the Cr(VI) oxidation state. To overcome the spectral interference caused by the matrix chloride ion in the resulting solutions, we employed cool plasma to successfully suppress chloride-based molecular ion interference during the inductively coupled plasma-mass spectrometry measurement. By significantly eliminating interference from the cationic and anionic components in the matrices prior to the inductively coupled plasma-mass spectrometry measurement, we found that the detection limit reached 0.18 μg L− 1 (based on 3 sigma). We validated this method through the analysis of the total chromium content in two reference materials (NIST 1643c and 2670E) and through measuring the recovery in spiked samples.