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    氯铂酸铵重量法-电感耦合等离子体原子发射光谱法测定铂炭催化剂中高含量铂

    Determination of Platinum with High Content in Platinum-Carbon Catalysts by Ammonium Chloroplatinate Gravimetric Method and Inductively Coupled Plasma Atomic Emission Spectrometry

    • 摘要: 为实现铂炭催化剂样品中高含量铂的低成本、准确测定,采用氯铂酸铵重量法测定主量铂,电感耦合等离子体原子发射光谱法(ICP-AES)测定微量铂,并以二者之和计算样品中铂的含量。称取0.200 0 g样品,加入10 mL盐酸和5 mL硝酸,于200 ℃加热10 min后加入5 mL高氯酸,于280 ℃加热至样品完全溶解。加入5 mL盐酸,于200 ℃蒸发至溶液近干,重复该步骤2次。收集残余物,加入2 mL盐酸和8 mL水,再边搅拌边缓慢加入(85±5) ℃的饱和氯化铵溶液50 mL,于150 ℃蒸发至溶液近干。冷却,边搅拌边加水,使残留的氯化铵晶体完全溶解,静置12 h。用定量滤纸过滤,洗涤沉淀,将滤纸包裹着的沉淀转移至已恒重的瓷坩埚中,用电炉在程序升温条件下加热至滤纸完全烘干并灰化,当白色烟雾消失时停止加热,取下瓷坩埚,于900 ℃灼烧2 h,冷却后称重,计算主量铂的质量分数。将滤液于180 ℃加热浓缩,待体积变小至有氯化铵晶体析出时,缓慢加入20 mL硝酸,于180 ℃继续加热以分解氯化铵,重复该步骤直至无氯化铵晶体析出,于180 ℃加热至溶液剩余约2 mL,加入10 mL盐酸加热至沸,冷却后用水稀释至100 mL,采用ICP-AES在分析谱线214.423 nm下测定微量铂。结果显示,ICP-AES所得铂的质量浓度在20.00 mg·L−1以内和谱线强度呈线性关系,检出限(3s)为0.013 8 mg·L−1;实际样品的10次重复测定的相对标准偏差为0.17%,标准加入法所得的铂的回收率为98.9%~103%。

       

      Abstract: To achieve low-cost and accurate determination of platinum with high content in platinum-carbon catalyst samples, ammonium chloroplatinate gravimetric method was adopted to determine the platinum with major content, while inductively coupled plasma atomic emission spectrometry (ICP-AES) was adopted to determine the platinum with trace content. The total platinum content in the sample was calculated as the sum of the above two. The 0.200 0 g of sample was taken, and 10 mL of hydrochloric acid and 5 mL of nitric acid were added. The mixture was heated at 200 ℃ for 10 min, followed by the addition of 5 mL of perchloric acid. The mixture was heated at 280 ℃ until the sample was completely dissolved. Then, 5 mL of hydrochloric acid was added, the solution was evaporated to near dryness at 200 ℃, and this step was repeated twice. The residue was collected, and 2 mL of hydrochloric acid and 8 mL of water were added. Subsequently, 50 mL of the saturated ammonium chloride solution at (85±5) ℃ was slowly added while stirring, and the solution was evaporated to near dryness at 150 ℃. After cooling, water was added while stirring to completely dissolve the remaining ammonium chloride crystals, and the solution was settled for 12 h. After filtering using quantitative filter paper, the precipitate was washed, which wrapped in the filter paper was transferred to a pre-weighed porcelain crucible and heated in an electric furnace under programmed temperature conditions until the filter paper was completely dried and ashed. Heating was stopped when white smoke disappeared, and the porcelain crucible was removed and calcined at 900 ℃ for 2 h. After cooling, the porcelain crucible was weighed, and the mass fraction of major platinum was calculated. The filtrate was heated and concentrated at 180 ℃. When the volume became smaller to the precipitation of ammonium chloride crystals, 20 mL of nitric acid was slowly added, the solution obtained was heated at 180 ℃ to decompose the ammonium chloride, and this step was repeated until no more ammonium chloride crystals precipitated. The solution was heated at 180 ℃ until approximately 2 mL remained, and 10 mL of hydrochloric acid was added. The solution was heated to boiling, and diluted with water to 100 mL after cooling. Trace platinum was determined by ICP-AES at the analytical wavelength of 214.423 nm. It was shown that linear relationship between values of the mass concentration and spectral line intensity of platinum was kept within 20.00 mg · L−1 for ICP-AES, with a detection limit (3s) of 0.013 8 mg · L−1. RSDs of 10 repeated determinations of the actual sample was 0.17%, and the recovery of platinum obtained by the standard addition method ranged from 98.9% to 103%.

       

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