半微量定氮法中三氯乙酸提取挥发性盐基氮的改进

Improvement on extraction of volatile basic nitrogen by trichloroacetic acid in semimicro-kjeldahl determination method

中文关键词:  三氯乙酸  氧化镁  挥发性盐基氮  半微量定氮法

英文关键词:trichloroacetic acid  MgO  volatile basic nitrogen  semimicro-kjeldahl determination method

中文摘要:

      目的 改进半微量定氮法中三氯乙酸提取挥发性盐基氮的条件。方法 比较了提取剂三氯乙酸和水的提取效果, 并优化了三氯乙酸作提取剂时氧化镁的添加量, 同时添加氯化铵做回收率实验。结果 按照标准方法用三氯乙酸浸泡的样品检测结果明显偏低, 其样品溶液碱度未能达到方法要求, 经调整氧化镁添加量后, 加标回收率为94.0%~95.6%, 相对标准偏差(relative standard deviation, RSD)为0.57%; 用水作提取剂的样品结果偏高, 浸泡30 min过程中, pH值中性环境样品持续腐败。结论 优化后的检验方法满足实验要求, 且三氯乙酸给样品提供足够的酸性环境, 抑制样品进一步腐败。

英文摘要:

      Objective To improve the extraction conditions of volatile basic nitrogen by trichloroacetic acid in semimicro-kjeldahl determination method. Methods The extraction effect of trichloroacetic acid and water was compared. The addition amount of magnesium oxide when trichloroacetic acid was used as extraction agent were optimized. At the same time, ammonium chloride was added for recovery experiment. Results The test result of samples soaked with trichloroacetic acid according to the standard method was obviously low. The alkalinity of sample solution failed to meet the method requirements. After adjusting the supplemental amount of magnesium oxide, the recoveries rate of spiked sample by the optimized method were 94.0%?95.6%, and the relative standard deviations (RSDs) were 0.57%. The result of the sample with water as the extractant was high, and the sample in the pH-neutral environment continued to rot after being immersed for 30 min. Conclusion The optimized test method meets the experimental requirements, and trichloroacetic acid provides sufficient acidic environment for the samples to inhibit further spoilage changes.