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    气体吸收-离子色谱法检测电子特气中痕量氟离子、铵根离子的捕集参数的优化

    Optimization of Capture Parameters for Detection of Trace Fluoride and Ammonium Ions in Electronic Specialty Gases by Ion Chromatography with Gas Absorption

    • 摘要: 提出了用于检测电子特气中氟离子(F)和铵根离子(NH4+)的气体吸收-离子色谱法,并以氮气中F为待测对象,通过对捕集效率的本质影响因素的探讨,确定了4个关键捕集参数捕集流量、捕集时间、吸收液用量和吸收瓶规格并采用正交试验进行优化。以聚丙烯(PP)材质吸收瓶吸收氮气中F,改性聚四氟乙烯(PFA)材质吸收瓶吸收氢气中NH4+,水为吸收液,采用自制气体吸收装置通过六步规范操作进行气体吸收试验,目标离子经浓缩柱富集后进入离子色谱仪,以标准曲线法测定,校准曲线法确定方法检出限。结果显示:优化的捕集参数为捕集流量0.5 L·min−1、捕集时间30 min、吸收液用量100 mL、吸收瓶规格φ3 cm×17 cm,且该参数适用于氢气中NH4+的测定;检测F和NH4+的标准溶液制作标准曲线,二者的质量分数均在20~500 μg·kg−1内和峰面积呈线性关系;利用氟化氢和氨气的标准气体制作校准曲线,每个浓度点的吸收率维持在74.0%~88.0%内,由校准曲线斜率计算得的氟化氢和氨气F或NH4+的方法检出限分别为4.8×10−9 mol·mol−1和4.9×10−9 mol·mol−1

       

      Abstract: The method of ion chromatography with gas absorption for detecting F and NH4+ in electronic specialty gases was proposed. With F in nitrogen as the test object, the essential influencing factors of capture efficiency was explored, and 4 key capture parameters, including capture flow, capture time, absorbent amount, and absorption bottle specification, were determined and optimized using orthogonal experiments. The polypropylene (PP) material absorption bottle was used to absorb F in nitrogen gas, the modified polytetrafluoroethylene (PFA) material absorption bottle was used to absorb NH4+ in hydrogen gas, and water was used as the absorbent. Gas absorption tests were conducted by the the self-made gas absorption device through 6 standardized operations. The target ions were enriched by the concentrating column, introduced into the ion chromatograph, and qualified by the standard curve method, and the calibration curve method was used to determine the method detection limit. It was shown that the optimized capture parameters were capture flow of 0.5 L·min−1, capture time of 30 min, absorbent amount of 100 mL, and absorption bottle specification of φ3 cm×17 cm, and these parameters were suitable for the determination of NH4+ in hydrogen gas. The standard curves were made by standard solutions of F and NH4+, and linear relationships between values of the mass fraction and peak area were kept in the range of 20-500 μg·kg−1. Calibration curves were made by standard gases of hydrogen fluoride and ammonia, giving the absorption rate of each concentration point in the range of 74.0%-88.0%, and method detection limits for hydrogen fluoride and ammonia were 4.8 × 10−9 mol · mol−1 and 4.9 × 10−9 mol · mol−1 (calculated by slopes of calibration curves), respectively.

       

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