Solid Phase Extraction of Mn, Co, Cr, Zn, and Pb on Titanium Dioxide Nanotubes for Their Determination by Inductively Coupled Plasma Mass Spectrometry

In this paper, the use of titanium dioxide nanotubes (TDNTs) as solid-phase extraction adsorbent for on-line microcolumn separation and preconcentration of trace metals (Mn, Co, Cr, Zn, and Pb) was investigated by inductively coupled plasma mass spectrometry (ICP-MS). The effects of the experimental parameters, including pH, sample flow rate and volume, elution conditions and interfering ions on the recoveries of the analytes were investigated systematically. The experimental results showed that the analytes were adsorbed quantitatively on TDNTs in the pH range from 7.0 to 9.0 and then eluted completely with 1.5 mol L-1 HNO3 solution. Under the optimum conditions, the detection limits of this method ranged from 0.3 pg mL(-1) (Co) to 15 pg mL(-1) (Zn) with a 150-fold enrichment factor; the relative standard deviations (RSDs) for the analytes were less than 4.5% (n=9, c=1.0 ng mL(-1)). The linear range of the calibration curve spanned three orders of magnitude. This method was applied to the determination of trace elements (Mn, Co, Cr, Zn, and Pb) in natural water samples with recoveries of 94.8-104%. In order to validate this method, the certified reference material GBW 07601 Human Hair was analyzed, and the determined values were in good agreement with the certified values.