Using Ion Chromatography to Simultaneously Measure the Concentrations of Organic and Inorganic Acid Anions in Acid Precipitation

• Main Authors: Sheng-Feng Chiu, 邱聖峯
• Other Authors: Wen-Liang Lai
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/66834581197740260880

碩士 === 大仁科技大學 === 環境管理研究所 === 93 === ABSTRACT The acid deposition can be divided both anions consisted of organic and inorganic acid. Hence, the air quality of ambient atomosphere, especially for thermal power plant, is not only to monitor the anions of inorganic acid, such as fluoride, chloride, nitrite, bromide, nitrate, and sulphate, but also to monitor the anion of inorganic acid, such as format and acetate. Owing to new technologies developed in ion chromatography (IC) resulted in its lower detection limit, it is a feasible tool in the laboratory in analyzing the concentrations of cation and anion species. Because Dionex 600, equipped with KOH effluent that autogenerated from EG-40 system and connected with OH-type of column for AS-17and AG17, can avoid the interference from carbonate ion dissolved from the air as well as increase its sensitivity, this system can be used to simultaneously effectively measure the anions of inorganic and organic. In our research, four operational parameters, included flow velocity, intensity of voltage, volume of water sample, and concentration of effluent, were used to evaluate its effect on difference between the retention time of approximate ions, such as, formate and acetate, nitrate and bromide, nitrite and chloride, and sulphate and phosphate. It found that the difference of retention time between approximate ions were dominantly affected by flow velocity and concentration of effluent. For the optimal condition of operation for flow velocity and concentration of effluent by central composite design, four pairs were different. Regarding to MDL (method detection limit) based on the optimal condition of nitrate and bromide, all anions were lower than 20 μg/L, and even less than 6μg/L for nitrite and bromide. Regarding the effect of pretreatment of four membrane filters, including cellulose acetate, mixed cellulose ester, Nylon(Whatman), and FP450 (Pall), usually used to filter water sample on the analysis of anions, it found that using FP450 as membrane filter was better than others due to only on specie released in process of immersion in pure water. Then, work solution contained eight anions of 0.5 mg/L was passed through four membrane filter preimmersed in pure water about 120 min. Although the concentration of all ions were decreased to through the membrane filter, the percent of decrease , only mixed cellulose ester was little. For long operation of IC system, the retention time of all ions analyzed became shorter than its value of start, but all species can still be distinguished. Also, the interference of fluoride on acetate should be cared. Two monitoring stations located at the surroundings of thermal power plant were selected to compare the difference of concentrations of both organic and inorganic anions in wet and dry precipitation. Based on the results investigated, sulphate, chloride and nitrate were dominant anions in dry precipitation for both monitoring stations, and its concentration in dry precipitation were higher than in wet precipitation. Furthermore, organic anions were detected in part of samples. It means that in addition of inorganic anion, enhancing controlling the amount of the organic anion is necessary for EPA in Taiwan for assuring good air quality of ambient environment.