Development of Electrothermal Vaporization/ICP-MS for Microtrace Analysis

为了有效地将微量样品引入ICP-MS，构建了一个可拆卸的样品进样器，该进样器带有螺旋钨丝。将体积为5 μl的样品置于灯丝上，将进样器插入等离子炬。样品脱溶后，电加热灯丝。产生的蒸汽被转移到等离子体中用于测定砷和硒。与之前的研究相比，信号强度增加了近100倍，在之前的研究中，环形钨丝在等离子炬外加热。砷和硒的绝对检出限分别为0.5 pg和1.1 pg。该方法可用于测定人发（5 mg）中砷和硒的含量。分析结果As为0.29±0.03 μg ^1， Se为1.8±0.2 μg ^1，与认证值As为0.31±0.02 μg/g， Se为2.0±0.08 μg/g符合较好。用0.50 mg重量的样品进行分析。用10 μl 14 mol/l HNO_3和2 μl 30% H_2O_2在聚四氟乙烯高压分解容器中分解样品。将所得溶液与25 μl的1 μmol/l KMnO_4溶液混合，蒸发至干燥。用1 mol/l HNO_3溶液500 μl溶解残渣。在样品中加入KMnO_4是防止分析物在蒸发过程中严重损失（30 ~ 50%）所必需的。砷含量为0.30±0.01 μg/g，硒含量为2.0±0.2 μg/g，与鉴定值基本吻合。该方法也适用于高纯铜（99.9999%）中硒的测定。样品（200 mg）酸分解后，取所得溶液5 μl直接置于灯丝上，测量^<82>Se+的信号强度。然而，铜基体显著降低了信号，并立即恶化了细丝。通过与氢氧化铁的共沉淀，有效地去除了样品溶液中的铜，从而成功地测定了样品中硒的μg/g水平。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