Quaresma Maria Cristina B, Cassella Ricardo J, Guardia Miguel de la, Santelli Ricardo E
Departamento de Geoquimica, Universidade Federal Fluminense, Niterói RJ 24020-007, Brazil.
Talanta. 2004 Mar 10;62(4):807-11. doi: 10.1016/j.talanta.2003.10.002.
An on-line automated flow injection system with microwave-assisted sample digestion was used to perform silicate rock dissolution in acid medium for iron determination. For this purpose, a continuous flow system was built up by using an automatic flow injection analysis (FIA) system coupled to a flame atomic absorption spectrometer (FAAS), including a focused microwave oven unit. Inside the microwave cavity was inserted a polytetrafluoroethylene (PTFE) reactor coil (300cm length and 0.8mm i.d.) where the dissolution takes place. Chemical and flow variables as well as iron determination parameters were studied. In the flow system, a slurry of the rock sample (50mg in 200ml of acid mixture HF+HCl+HNO(3)) is pumped through the reaction coil and the microwaves are turned on. After elapsed the time required to complete the sample dissolution, the mixture is pumped again in order to fill the sampling loop (500mul). Then, by changing the valve position, a water carrier stream pushes the sample solution through the flame atomic absorption spectrometer nebulizer. To achieve an accurate determination of the rock certified materials, the slurry sample was irradiated during 210s at 90W power. Working in that condition, a detection limit of 0.80mugml(-1) (which corresponds to an Fe(2)O(3) content of 0.46%) and an analytical throughput of 10h(-1) were achieved. The relative standard deviation (R.S.D.) of the method varied between 1 and 11% when applied to the rock certified materials.
采用带有微波辅助样品消解的在线自动流动注射系统，在酸性介质中进行硅酸盐岩石溶解以测定铁含量。为此，通过将自动流动注射分析（FIA）系统与火焰原子吸收光谱仪（FAAS）联用，并配备聚焦微波炉单元，构建了一个连续流动系统。在微波腔内插入一个聚四氟乙烯（PTFE）反应盘管（长度300cm，内径0.8mm），溶解过程在此盘管中进行。研究了化学和流动变量以及铁测定参数。在流动系统中，将岩石样品浆液（50mg于200ml酸混合物HF + HCl + HNO₃中）泵入反应盘管并开启微波。在完成样品溶解所需时间过去后，再次泵送混合物以填充采样环（500μl）。然后，通过改变阀的位置，载水流将样品溶液推过火焰原子吸收光谱仪的雾化器。为了准确测定岩石标准物质，将浆液样品在90W功率下辐照210s。在此条件下工作，实现了0.80μg ml⁻¹的检测限（相当于Fe₂O₃含量为0.46%）和10 h⁻¹的分析通量。当应用于岩石标准物质时，该方法的相对标准偏差（R.S.D.）在1%至11%之间变化。
