采用一种具有平头结构的pH电极作为流动注射分析(FIA)的检测器,构建了流动注射自动化酸度滴定系统.优化了样品进样量、流速、载液浓度和反应管长度等参数.用NaOH溶液作为载液,在4.639×10-4～0.212 mol·L-1范围内醋酸浓度的对数与FIA峰的峰面积成正比,该方法的相对标准偏差(RSD)小于0.5%.采用该方法对市售4种食醋样品的检测结果与国家标准方法(酸碱滴定法)一致,但灵敏度是普通手工滴定方法的10倍,分析速度可达60样/h.只需改变载液NaOH浓度,即可用于滴定其他浓度范围的醋酸样品.%A new flow injection analysis(FIA) system with a flat pH electrode was established for the rapid determination of acetic acid in vinegar. The FIA system was optimized by alteration of injection volume, flow rate, carrier concentration and length of reaction tubes. With sodium hydroxide solution as carier stream, the peak area obtained from the lab assembled FIA system were proportional to the logarithm concentration of acetic acid in the range of 4. 639 × 10-4 -0. 212 mol · L-1. The method was applied in the detection of acetic acid in four vinegar samples, and the results obtained were in good agreement with those obtained by the standard manual titration method. The sensitivity of this method was ten times higher than that of the conventional titration method, and the analysis rate was up to 60 samples per hour. By changing the concentration of carrier stream ( sodium hydroxide), the acetic acids at different concentration levels can be titrated without any other adjustments to the FIA system.
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