Development of Electrothermal Vaporization/ICP-MS for Microtrace Analysis

为有效地将微量样品引入电感耦合等离子体质谱(ICMS)，研制了一种可拆卸的钨丝进样器。将5μL体积的样品放在灯丝上，将进样器插入等离子炬。样品脱溶后，对灯丝进行电加热。产生的蒸气被转移到等离子体中，以测定As和Se。与之前的一项研究相比，信号强度增加了近100倍，在之前的研究中，将环形钨丝加热到等离子火炬外部。方法的绝对检出限分别为0.5pg和1.1pg，用于标准参照物头发(5 Mg)中砷和硒的测定。As和Se的分析结果分别为0.2 9±0.0 3μg g^1和1.8±0.2μg g^1，与标准值(0.31±0.0 2μg/g和Se2.0±0.0 8μg/g)一致。用0.50毫克重量的样品进行了分析。样品是DECO…在聚四氟乙烯高压分解罐中加入10μ的L和2μ的30%H_2O_2。所得溶液与25μL的1μ/L高锰酸钾溶液混合，蒸发至干燥。残留物用500μL溶液溶解。加入高锰酸钾可防止分析物在蒸发过程中严重损失(30%~50%)。结果表明，砷的测定值为99.9999.30±0.0 1μg/g，硒的测定值为2.0±0.2μg/g，并用于高纯铜中硒的测定。样品酸解后，将所得溶液中的5μL部分直接放置在灯丝上，测量^&lt；82&gt；Se+的信号强度。然而，铜基质显著降低了信号，并立即恶化了细丝。用氢氧化铁共沉淀法有效地去除了样品溶液中的铜，从而成功地测定了样品中μg/g的Se。较少

A detachable sample-injector with a coiled tungsten filament was constructed for the effective introduction of tiny amounts of sample into ICP-MS. A 5 μl volume of the sample was placed on a filament and an injector was inserted into a plasma torch. After desolvating the sample, the filament was electrically heated. The resulting vapor was transferred to the plasma for the determination of As and Se. The signal intensities increased by almost 100 times as compared with the values in a previous study, where a looped tungsten filament was heated outside the plasma torch. The absolute detection limits were 0.5 pg for As and 1.1 pg for Se.The proposed method was applied to the determination of As and Se in certified reference human hair (5 mg). The analytical results were 0.29±0.03 μg g^1 for As and 1.8±0.2 μg g^1 for Se, which are in good agreement with the certified values (As 0.31±0.02 μg/g, Se 2.0±0.08 μg/g). The analysis was tried with 0.50-mg weight of the sample. The sample was deco … More mposed with 10 μl of 14 mol/l HNO_3 and 2 μl of 30% H_2O_2 in a PTFE high-pressure decomposition vessel. The resulting solution was mixed with 25 μl of 1 μmol/l KMnO_4 solution and evaporated to dryness. The residue was dissolved in 500 μl of 1 mol/l HNO_3. The addition of KMnO_4 to the sample was essential for the prevention of serious losses (30〜50%) of analytes during evaporation. The results (0.30±0.01 μg/g for As and 2.0 ± 0.2 μg/g for Se) agreed closely with the certified values.The proposed method was also applied to the determination of Se in high-purity copper (99.9999%). After the acid decomposition of a sample (200 mg), a 5 μl portion of the resulting solution was directly placed on a filament and the signal intensities of ^<82>Se+ were measured. Copper matrix, however, significantly decreased the signals and immediately deteriorated filaments. Copper in the sample solution was effectively removed by coprecipitation with iron hydroxide, and consequently, μg/g level of Se in the sample was successfully determined. Less