After HNO3, HF, HClO4 and H2SO4 were added into sample in sequence, it was heated on electric furnace at 160 ℃ for 1 h and the temperature was increased to 240 ℃ until the white smoke disappeared, then HNO3 was added for re-dissolution at 180 ℃.The content of cadmium was determined under standard (STD) mode, while molybdenum, tungsten, uranium and tin were determined under kinetic energy discrimination (KED) mode.Consequently, an analysis method of molybdenum, cadmium, tungsten, uranium and tin in geochemical samples by inductively coupled plasma mass spectrometry (ICP-MS) was established.The mass spectrometry interference was eliminated by selecting proper isotopes, determination mode and correction formulas.The matrix effect and signal drift was corrected with 10 ng/mL 187Re and 103Rh as mixed internal standard.Under the optimized experimental conditions, the linear correlation coefficients of calibration curves of elements were all higher than 0.999.The detection limit of molybdenum, cadmium, tungsten, uranium and tin was 0.068 9, 0.002 0, 0.092 6, 0.123 and 0.089 6 μg/g, respectively.The content of molybdenum, cadmium, tungsten, uranium and tin in geochemical actual samples was determined according to the proposed method.The relative standard deviations (RSD, n=6) were between 2.4% and 4.8%, and the recoveries were between 91% and 114%.The proposed method was applied to the determination of those five elements in certified reference materials of stream sediment, soil and rock.The results were consistent with the certified values.%在样品中依次加入HNO3、HF、HClO4、H2SO4,在电炉上于160 ℃加热1 h,后升至240 ℃加热至白烟冒尽,180 ℃下再加入HNO3复溶,以普通(STD)模式测定Cd,以动能歧视(KED)模式测定Mo、W、U、Sn,建立了电感耦合等离子体质谱法(ICP-MS)测定地球化学样品中Mo、Cd、W、U、Sn的方法.通过选用合适的同位素、测定模式和校正公式克服了质谱干扰;以10 ng/mL 187Re和103Rh为混合内标进行校正消除了基体效应和仪器信号的漂移.在优化的实验条件下,各元素校准曲线的线性相关系数均大于0.999,Mo、Cd、W、U、Sn检出限分别为0.068 9、0.002 0、0.092 6、0.123、0.089 6 μg/g.按照实验方法对地球化学实际样品中Mo、Cd、W、U、Sn进行测定,测得结果的相对标准偏差(RSD,n=6)为2.4%~4.8%,回收率在91%~114%之间.将实验方法应用于水系沉积物、土壤、岩石标准物质中这5种元素的测定,结果与认定值相符.
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