ALS Laboratory Group, ALS Scandinavia AB, Aurorum 10, 977 75 Luleå, Sweden.
Anal Chim Acta. 2010 Dec 3;682(1-2):59-65. doi: 10.1016/j.aca.2010.09.049. Epub 2010 Oct 7.
The ferrihydrite-backed DGT (diffusive gradients in thin films), recently developed for arsenic and phosphate measurements was, for the first time, characterized with respect to molybdate, antimonate, vanadate and tungstate determination. Arsenate was included in the characterization to allow comparison with literature data and thus provide quality control of the measurements. In addition to laboratory experiments, field measurements were carried out in a natural stream in northern Sweden affected by mine drainage. It was shown that ferrihydrite-DGT is suitable for simultaneous determination of labile arsenic, molybdate, antimonate, vanadate and tungstate over a wide pH range. Diffusion coefficients were estimated using two different methods; diffusion cell and direct uptake to DGT devices in synthetic solutions. Estimations of the coefficients using the direct uptake method were performed between pH 4 and 8. The results from the two methods agreed well irrespective of pH, except for molybdate and antimonate that showed decreased values at pH 8. Adsorption of the analytes to ferrihydrite gel-discs was rapid at all pH values. However, there was a tendency toward lower adsorption affinity for antimonate compared to the other anions. 100% recovery of accumulated analytes was achieved through complete dissolution of the ferrihydrite adsorbent using 1.4 molL(-1) HNO(3) with 0.1 molL(-1) HF. From field sampling it was concluded that the opportunities for accurate antimonate and molybdate determination decrease at pH≥8.7. DGT-labile concentrations were generally lower than dissolved concentrations. Relatively lower DGT concentrations, compared to dissolved (<0.45 μm), were observed under a period when ferric oxide precipitations were detected on the DGT protective filter.
铁氢氧化物支持的 DGT（薄膜扩散梯度）最近被开发用于砷和磷酸盐的测量，首次针对钼酸盐、锑酸盐、钒酸盐和钨酸盐的测定进行了特征描述。砷酸盐也包括在特征描述中，以便与文献数据进行比较，从而对测量进行质量控制。除了实验室实验外，还在瑞典北部受矿山排水影响的天然溪流中进行了现场测量。结果表明，铁氢氧化物 DGT 适合在宽 pH 范围内同时测定活性砷、钼酸盐、锑酸盐、钒酸盐和钨酸盐。使用两种不同的方法（扩散池和直接吸收到 DGT 装置中）估算扩散系数；在合成溶液中。使用直接吸收方法估算的系数在 pH 4 至 8 之间进行。两种方法的结果无论 pH 值如何都非常吻合，除了钼酸盐和锑酸盐在 pH 8 时显示出较低的值。在所有 pH 值下，分析物在铁氢氧化物凝胶圆盘上的吸附都很快。然而，与其他阴离子相比，锑酸盐的吸附亲和力较低。通过使用 1.4 mol/L 的 HNO(3)和 0.1 mol/L 的 HF 完全溶解铁氢氧化物吸附剂，可实现累积分析物的 100%回收率。从现场采样中得出结论，在 pH≥8.7 时，准确测定锑酸盐和钼酸盐的机会减少。DGT-可溶浓度通常低于溶解浓度。在 DGT 保护过滤器上检测到氧化铁沉淀的一段时间内，与溶解的（<0.45 μm）相比，DGT 的浓度相对较低。
