增压消解-电感耦合等离子体质谱法测定硅藻土中26种微量元素

提出用增压消解法消解硅藻土样品可使其所含的铌、钽、锆、铪等高场强元素溶解,从而达到所测定的26种微量元素完全溶解。操作时取样0.10g,置于消解罐的聚四氟乙烯(PTFE)内罐中,加少量水湿润样品,然后加入硝酸2mL和氢氟酸5mL,将消解罐密闭盖紧,置于保温185℃的烘箱中消解24h后,冷却,取出内罐,加入硝酸1mL,在电热板上蒸发至近干,重复3次加入硝酸并蒸干,以驱尽氢氟酸。然后于残渣中加入HCl-HNO3-H2O(体积比为3∶1∶4)混合酸5mL,将此内罐回置于外罐中,加盖密闭,再置于控温在185℃烘箱中消解8h,冷却后取出内罐,将其中溶液定容至25.0mL。分取此溶液5.0mL,加水定容至25mL。此溶液作为试溶在选定的仪器工作条件下进行电感耦合等离子体质谱分析。测得各元素的质量浓度在一定范围内与所测得的响应值与内标响应值的比值呈线性关系。各元素的检出限(3s)为0.003~0.2μg·g^-1。在制作标准曲线及样品分析时,均在最终的测试溶液中加入103 Rh(10μg·L^-1)作为内标。用本方法分析了国家标准物质,所得测定值与其认定值相符。各测定值的相对标准偏差(n=8)为1.3%~5.6%。对我国3个主要矿区的硅藻土样品进行分析,并绘制了球粒陨石归一化的稀土配分曲线图,发现3种样品都表现为轻稀土含量高于重稀土,都具有比较平滑的配分曲线,但存在铕的负异常。这些规律与文献的报道一致。

Determination of 26 Trace Elements in Diatomite by ICP-MS with Digestion in Pressure Vessel

Sample dissolution in ICP-MS determination of 26trace elements in diatomite was modified by digestion in pressure vessel and complete dissolution of sample including the high field strength elements of niobium,tantalum,zirconium,hafnium was attained.0.10g of the sample was placed into the PTFE inner vessel,and after moistening with a small amount of water,2mL of nitric acid and 5mL of hydrofluoric acid were added.The inner vessel was then placed into the outer digestion vessel,and after sealing hermetically,it was digested for 24hin a drying oven controlled at 185℃.After cooling,the PTFE inner vessel was taken out,after addition of 1mL of nitric acid the solution in the vessel was evaporated to near-dryness.The addition of nitric acid and evaporation to near-dryness were repeated for 3times to expel hydrofluoric acid completely.Then 5mL of mixed acid of HCl+HNO3+H2O with a volume ratio of 3∶1∶4were added to the residue,and the inner vessel with the solution mixture was placed back into the outer vessel.The digestion vessel was hermetically sealed and digested again in the oven at 185℃for 8hto attain complete dissolution.At the end of digestion,the digestion vessel was cooled to room temperature,the inner vessel containing the sample solution was taken out and the volume of the solution was made up to 25mL with water.An aliquot of 5.0mL from the solution was taken and made up its volume to 25mL with water.This solution was used for ICP-MS analysis under the optimum working condition of the interument.103 Rh was added to either the sample solution and the mixed standard solutions for preparation of standard curves to have a concentration of 10μg·L^-1 as internal standard.Linear relationships between values of ratios of response determined to the response of the internal standard and the mass concentrations of the 26elements in definite ranges were found.Detection limits(3s)found for the 26elements were in the range of 0.003-0.2μg·g^-1.A CRM(GBW 07107)was analyzed by the present method,giving results in consistency with the certified values.Values of RSDs(n=8)found for the 26elements were in the range from 1.3%-5.6%.Three diatomite samples taken separately from 3main mining areas in our country were analyzed by this method,and the chondritenormalization patterns of rare earth elements was prepared.It was found that contents of light rare earth elements were higher than the contents of heavy rare earth elements for all the 3samples,and that the 3pattern curves showed very smooth trend and same well defined negative anomaly of europium.The results were in consistency with those reported in literatures.