フローインジェクション分析法によるボイラ給水中の微量ヒドラジンの吸光光度定量

Trace amounts of hydrazine in boiler feed water were determined by a flow injectionspectrophotometric method with p-dimethylaminobenzaldehyde (DMBA). The DMBA solution for the color development was prepared by dissolving it in diluted hydrochloric acid without using any organic solvents such as alcohols. The reagent solution proposed in this work had several advantages, compared with the alcoholic solution usually used in the batchwise spectrophotometric method. The solution was easily prepared with hydrochloric acid and water, stable for longer times and did not evolve when the solution was mixed with sample solutions, and the waste treatment was easier than for the alcoholic solution. A carrier (H(2)O)and the reagent solution were propelled at flow rates of 1.0 ml min(-1) and 0.6 ml min(-1), respectively. They were merged to flow into a reaction coil (0.6 mm i.d.×6 m) kept in a temperature-controlled air bath at 80℃.Samples were injected into the carrier stream, and the reaction product was measured at 458 nm. Metal ions and ammonia did not interfere with the determination of hydrazine. The calibration graph was linear up to 100 ppb of hydrazine, and the detection limit corresponding to a signal to noise ratio of 3 was 0.2 ppb.Relative standard deviations for seven replicates of 5, 50 and 100 ppb of hydrazine were 1.1, 0.9 and 0.4%, respectively. The proposed method was applied to the determination of hydrazine in boiler feed water samples.

火力発電所のボイラ給水中に脱酸素剤として添加され,酸素と反応後残留している微量ヒドラジンのフローインジェクション-吸光光度定量について,p-ジメチルアミノベンズアルデヒド(DMBA)を用いて検討を行った.DMBAを用いる従来のバッチ式マニュアル分析法では,DMBAの溶解に塩酸と多量のアルコールを用いているが,試薬液調製の簡便化,取り扱いの容易さ,廃液処理の容易さから,アルコールを全く用いない反応系の開発について検討した.その結果,水と塩酸で調製した反応試薬液を用いても,従来法の反応試薬液と比較すると若干感度は劣るが十分定量に使用できることが分かった.FIAへの適用の詳細な検討の結果,検量線は0~100ppbの範囲で良好な直線性が得られた.S/N=3に相当する検出限界は0.2ppbであり,5ppbのヒドラジン試料に対する相対標準偏差は1.1%であった.本FIAは,共存金属イオンの影響もなく,微量ヒドラジンのボイラ給水管理分析に適用可能であることが分かった.