为解决高纯石墨样品前处理中高温灰化耗时长(4~10 h)的问题,提出了题示方法。取高纯石墨样品0.300 0 g,置于50 mL聚丙烯样品管中,用15 mL 10%(体积分数)王水(体积比为3∶1的盐酸-硝酸混合液)超声提取20 min,提取时会有部分石墨漂浮于液面上,用注射器吸取样品管中部的提取液约3 mL,过0.45 μm水系滤膜后收集在样品管中,在灰化温度为900 ℃、原子化温度为2 000 ℃等条件下采用石墨炉原子吸收光谱法进行测定。结果表明,超声提取缩短了样品处理时间(仅为20 min)。铅元素的质量浓度在5~50 μg·L^-1内与对应的吸光度呈线性关系,检出限(3s/k)为0.11 mg·kg^-1。对同一样品分析7次,测定值的相对标准偏差为4.6%。按照标准加入法进行回收试验,回收率为91.0%~94.0%。

In order to solve the time-consuming problem of high-temperature ashing (4-10 h) in the pre-treatment of high purity graphite samples, a method mentioned by title was proposed. The high purity graphite sample (0.300 0 g) was taken and placed into a 50 mL-polypropylene sample tube, and 15 mL of 10% (volume fraction) aqua regia (a mixture of hydrochloric acid and nitric acid at a volume ratio of 3∶1) solution was added for ultrasonic extraction for 20 min. Some graphite floated on the liquid surface in extraction process, so 3 mL of the extraction solution was sucked from the middle of the sample tube with a syringe, and passed through 0.45 μm water system filter membrane. The filtrate was collected into a sample tube and determined by graphite furnace atomic absorption spectrometry under the conditions such as ashing temperature at 900 ℃ and atomization temperature at 2 000 ℃. As shown by the results, ultrasonic extraction shortened the sample processing time (only 20 min). Linear relationship between the corresponding absorbance and mass concentration of Pb was found in the range of 5-50 μg·L^-1, with detection limit (3s/k) of 0.11 mg·kg^-1. The same sample was analyzed 7 times, with RSDs of the determined values of 4.6%. Test for recovery was made by standard addition method, giving results in the range of 91.0%-94.0%.