Speciation of inorganic arsenic in environmental waters using magnetic solid phase extraction and preconcentration followed by ICP-MS

A new method was developed for the speciation of inorganic arsenic in environmental water by using selective magnetic solid-phase extraction followed by inductively coupled plasma mass spectrometry. It is found that As(V) selectively adsorbed on amino-modified silica-coated magnetic nanoparticles (MNPs) in the pH range from 3 to 8, while As(III) is not be retained. The As(V)loaded MNPs can be separated easily from the aqueous sample solution by simply applying an external magnetic field. The adsorbed As(V) was quantitatively recovered from the MNPs using using 1 M nitric acid. Total inorganic As was extracted after the permanganate oxidation of As (III) to As(V). Parameters affecting the separation were investigated systematically, and the optimal separation conditions were established. Under the optimal conditions, the limit of detection is 0.21 ng L-1, and the precision is 6.8% (at 10 ng L-1, for n = 7). The method was applied to the speciation of inorganic arsenic in environmental water of tobacco growing area.