Yankuang ceshi (Sep 2017)
On-line Determination of Hg (Ⅱ) in Geological Samples by AFS after Solid Phase Extraction Using Dithizone-modified Graphene Oxide/Chitosan Composite Microspheres
Abstract
Mercury can indicate the presence of deposits or mineralization, which is an important tracer element of geological processes, thus making the determination of mercury very important. Due to the low abundance of mercury in ore deposits, it is difficult to directly determine and thus pre-separation enrichment is needed. Presently, most of the separation and preconcentration methods are off-line with a low degree of automation. Graphene oxide/chitosan microspheres modified by dithizone were prepared and applied as adsorption materials for solid phase extraction column. The effect of experimental parameters including acidity, adsorbent type, and adsorption volume on the absorption efficiency was evaluated. Sampling/elution time and the sampling/elution rate during solid phase extraction were optimized. Based on these conditions, an analytical method for the determination of trace mercury in geological samples by on-line enrichment-atomic fluorescence spectrometry with solid phase extraction was established. The results show that when the pH value is 3.0, the adsorption rate of mercury is more than 90% at 5 mL/min sampling rate. The elution rate was >95% when 20 g/L of thiourea and 1.0 mol/L HNO3 were used as elution solution and elution for 1 min at the rate of 1 mL/min. The working curve showed a good linear relationship when the concentration was between 0.050 μg/L and 5.0 μg/L. The enrichment factor was 22 and the detection limit was 0.0019 μg/L. The relative error of the measured value of Hg and the reference value was less than ±13% when this method was used to determine soil and sediment national standard materials. Compared with the off-line analysis, this method has advantages such as high sensitivity and simple operation.
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