Pytlakowska Katarzyna, Dabioch Marzena, Sitko Rafal
University of Silesia, Institute of Chemistry, ul. Szkolna 9, 40-006 Katowice, Poland.
Analyst. 2014 Aug 21;139(16):3911-7. doi: 10.1039/c4an00414k.
An ultrasound-assisted methodology for the determination of dissolved silicate in water has been developed by combining the miniaturized ion-associated based preconcentration method with energy dispersive X-ray fluorescence spectrometry (EDXRF). The method has been devised for the determination of silicate through molybdenum in the ion-associated complex between 12-molybdosilicate and crystal violet. Because silicate is determined indirectly via molybdenum fluorescent radiation the difficulties resulting from low fluorescence yield and low energy of silicon radiation were successfully overcome. A good ratio of silicon to molybdenum (1 to 41) and a sensitive Kα line of molybdenum make possible the determination of low concentration of silicon in the form of dissolved silicate. Under optimized conditions, good linearity, up to 5 μg of silicon in the form of silicate (r = 0.9990) and a detection limit of 9 ng mL(-1) were achieved. The total RSD for the EDXRF determination of silicate, followed by precipitation of the ion-associated complex and its dissolution in a microdrop of isoamyl alcohol, was 6.5%. The enrichment factor was equal to 142. The developed method was used to determine the dissolved silica content in surface waters. The accuracy and repeatability of the proposed procedure were checked by the standard addition method and compared to the results obtained using the ICP-OES technique. The recovery (in the 93-97% range) was satisfactory and indicated the usefulness of the developed procedure.
通过将基于离子缔合的微型预浓缩方法与能量色散X射线荧光光谱法（EDXRF）相结合，开发了一种用于测定水中溶解硅酸盐的超声辅助方法。该方法是通过12-钼硅酸盐与结晶紫之间的离子缔合络合物中的钼来测定硅酸盐。由于硅酸盐是通过钼荧光辐射间接测定的，因此成功克服了硅辐射荧光产率低和能量低所带来的困难。硅与钼的良好比例（1比41）以及钼灵敏的Kα线使得以溶解硅酸盐形式存在的低浓度硅的测定成为可能。在优化条件下，实现了良好的线性关系，硅酸盐形式的硅含量高达5μg（r = 0.9990），检测限为9 ng mL⁻¹。通过离子缔合络合物沉淀并溶解在异戊醇微滴中后，采用EDXRF测定硅酸盐的总相对标准偏差为6.5%。富集因子等于142。所开发的方法用于测定地表水中的溶解二氧化硅含量。通过标准加入法检验了所提方法的准确性和重复性，并与使用电感耦合等离子体发射光谱法（ICP-OES）获得的结果进行了比较。回收率（在93 - 97%范围内）令人满意，表明所开发方法的实用性。
