Abstract:
The method of ion chromatography with gas absorption for detecting F
− and NH
4+ 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 NH
4+ 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 NH
4+ in hydrogen gas. The standard curves were made by standard solutions of F
− and NH
4+, 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.