Titanium Dioxide Nanotubes for Speciation of Inorganic Arsenic in Environmental Water Samples by ICP-MS

In this paper, titanium dioxide nanotubes (TDNTs) were used as a new solid phase extraction adsorbent for on-line separation and preconcentration of inorganic arsenic species [As(III) and As(V)] prior to the determination by inductively coupled plasma mass spectrometry (ICPMS). The experimental results showed that in the pH range of 3.0-6.0, As(III) and As(V) were quantitatively retained on TDNTs. As(III) was only quantitatively adsorbed by TDNTs within the pH range of 6.0-10, while As(V) passed directly through the microcolumn without retention. Based on the facts mentioned above, a novel method was developed for the speciation of inorganic arsenic by determining total As and As(III) at the pH of 5.0 and 9.0, respectively; As(V) was obtained from the difference between them. The main factors affecting the separation and determination of the analytes were also examined in detail. Under the optimized conditions, the detection limit of this method was 0.0019 ng mL(-1) for As(III) with an enrichment factor of 75, and the relative standard deviation was 2.5% for As(III) (n=9, c=1.0 ng mL(-1)). This method was applied for the determination of inorganic arsenic species in environmental water samples in the recovery range of 95.5-102%. In order to verify the accuracy of the method, a certified reference water sample was analyzed with satisfactory results.