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中文摘要：
针对现有乙基纤维素乙氧基测定方法的不足,提出一种用顶空气相色谱（HS-GC）测定乙基纤维素乙氧基含量的方法——在顶空瓶中通过氢碘酸与乙基纤维素反应,使乙氧基转化为碘乙烷,反应结束后加碱液中和过量氢碘酸防止腐蚀进样器和色谱柱,随后顶空进样进行气相色谱分析,以甲苯为内标物,采用内标法测定碘乙烷含量,从而计算得出乙基纤维素乙氧基含量.考察了水解温度和时间、顶空进样器内平衡温度和时间、基质效应等因素对测定结果的影响,结果表明：水解温度在140～150℃范围内时,结果随温度变化不大,1.0h可完成水解反应;顶空瓶内样品在80℃下经30min可达到气液平衡;添加纤维素可消除基质效应,碘乙烷浓度与峰面积呈良好的线性关系.文中还研究了该方法的重现性与加样回收率,发现该方法重现性较好,乙氧基含量测定结果的相对标准偏差为2.83%,加样回收率达99.6%.将该方法与化学滴定法比较,可得到一致的样品测定结果.
英文摘要：
In order to overcome the disadvantages of the existing content determination methods of ethoxyl in ethyl cellulose,a new method based on the headspace gas chromatography（HS-GC） is proposed.In this method,first,ethyl cellulose is conversed into ethyl iodide by reacting with hydriodic acid.Next,sodium hydroxide is added in headspace sample vials to neutralize excessive hydroiodic acid before the HS-GC performance,thus avoiding the damage to the sample injection system and the column.Then,toluene is used as the internal standard to perform a HS-GC process.Finally,the content of ethoxyl in ethyl cellulose is determined according to the ethyl iodide content obtained by the internal standard method.The authors investigate the effects of hydrolysis temperature,hydrolysis time,equilibration temperature,equilibration time and matrix additive on the determination and find that,when the hydrolysis temperature ranges from 140 to 150 ℃,the determination results vary slightly and the reaction ends within 1.0 h,that a vapor-liquid equilibrium is reached at 80 ℃ after a vial equilibration for 30 min,that the addition of cellulose helps to eliminate the matrix effect and to obtain good linearity between ethyl iodide content and peak area.The authors also indicate that the proposed method is of good repeatability and average recovery because the RSD（Relative Standard Deviation） of determination results is very low（2.83%） and the recovery rate is very high（99.6%）,and that results obtained by the proposed method accord well with those obtained by chemical titration.
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