正交试验设计在茶叶铁、锌、铜含量测定中的应用

Application of Orthogonal Experimental Design in the Determination Condition of Fe,Zn,Cu in Tea

探究茶叶铁、锌、铜含量测定的最佳前处理条件。利用微波消解法,应用正交试验设计中的L9(34)正交表,拟通过改变消解硝酸含量、温度、消解压力、保持时间4个研究因素,对茶叶前处理过程中的前处理条件进行优化,以加标回收率作为评价指标,用火焰原子吸收光谱法测定茶叶中铁、锌、铜含量,拟寻求该元素的最佳前处理条件。结果表明,影响微量元素Fe的微波消解效果的因素依次为硝酸含量、消解压力、保持时间和温度,微波消解的最佳组合条件为:硝酸含量6 mL,温度190℃,消解压力50 bar,保持时间20 min。影响微量元素Zn的微波消解的因素依次为保持时间、温度、硝酸含量和消解压力,其最优消解条件为:硝酸含量8 mL,温度190℃,消解压力50 bar,保持时间25 min。影响微量元素Cu的微波消解的因素依次为温度、保持时间、硝酸含量以及消解压力,其最优消解条件为:硝酸含量为8 mL,温度为170℃,消解压力为60 bar,保持时间为15 min。

To explore the best pretreatment conditions for the digestion of Fe,Zn and Cu in tea. Microwave digestion technique was used to pretreat the samples. It was proposed to change the resolution of nitric acid content,temperature,digestion pressure and hold time by four research factors,and the L9(34)orthogonal table in the orthogonal design was used to optimize the pretreatment conditions in the tea pretreatment process. The recovery rate was used as the evaluation index. The content of Fe,Zn and Cu in tea was determined by flame atomic absorption spectrometry. The optimum pretreatment conditions for the element were sought. The order of the impact factors of microwave digestion of Fe were nitric acid content,digestion pressure,hold time and temperature. The best pretreatment conditions for microwave digestion were nitric acid 6 mL and temperature 190 ℃ and digestion pressure 50 bar,and hold time 20 min. As for Zn,the order of the impact factors was the hold time,followed by the temperature,then the nitric acid content,and finally the digestion pressure. The optimal digestion conditions were as follows:nitric acid content was 8 mL,and temperature was 190 ℃,and digestion pressure was 50 bar,hold time was 25 min. The order of factors affecting the microwave digestion effect of Cu in tea was temperature,holding time of pressure,HNO3 consume,and pressure. The best combination of sample pretreatment conditions found in this experiment was a HNO3 consume of 8 mL,a temperature of 170 ℃,a pressure of 60 bar,a holding time of pressure of 15 minutes.