利用排除法对影响氨氮实验室空白测定的各种因素进行了考察.结果表明,固定剂硫酸的添加不会引起空白值偏高.滤纸因含有铵盐会引起空白偏高,但可采取用去离子水浸泡的方法消除.絮凝沉淀过程中应避免将水体pH调至9.0左右.在水体pH =9.0左右时,沉淀物颗粒尺寸最小,过滤时渗入滤后液中,影响吸光度；过滤后的滤液pH会降低,导致滤液中重新析出沉淀物,也影响吸光度.%The factor that afects determination of ammonia nitrogen blank value in water was investigated through exclusive method. Result shows that no obvious variation was observed for blank value when sulfuric acid was added. Filter paper will cause blank value high due to containation of ammonium salt, and the phenomenon can be eliminated by immersion in deionized water. The value of pH should be avoided being adjusted to ca. 9. 0 during flocculating settling step. Particle size of precipitate prepaired at pH =9. 0 is the smallest, that can enters into filtrate leading to impaction on absorption value. The value of pH will decrease after filtration causing re-precipitation, then also makes influence on absorption value.
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