离子选择电极法测定土壤中水溶性氟提取液温度的控制方式

采用超声提取法对样品进行预处理,利用离子选择电极法测定土壤中的水溶性氟,超声空化热效应会造成提取液温度升高,检测结果不稳定,不能如实反映土壤中水溶性氟含量,对土壤环境中氟的监测造成困扰。因此,选择有效的控制提取液温度方式至关重要。本文通过记录直接超声、加冰袋、加冰水、冷却循环水四种温度控制方式提取液温度变化确定出最佳温度控制方式;选取具有稳定性和代表性的土壤有效态成分分析标准物质测定土壤水溶性氟含量,以验证最佳温度控制方式的合理性和有效性;同时分析了提取过程中提取液pH值变化,探讨温度对土壤中水溶性氟提取量影响的原因。结果表明:冷却循环水温度控制方式可有效将提取液温度控制在25±2℃内,该方式的相对误差(8.9%)明显小于直接超声(14.1%);提取液pH值无明显变化,测定结果稳定可靠。

The Control Mode of Extraction Temperature for Water-soluble Fluorine in Soils Measurement by Selective Electrode Method

BACKGROUND:The water-soluble fluoride in soil was pretreated by ultrasonic extraction and determined by ion selective electrode.The thermal effect of ultrasonic cavitation can cause the temperature of the extract to rise,and the test result may be unstable,and it cannot truthfully reflect the water-soluble fluorine content in the soil,which causes problems for the monitoring of fluorine in the soil environment.Therefore,how to effectively control the extraction temperature is the focus of this study.OBJECTIVES:To select the optimal temperature control method,verify the accuracy of the results,and preliminarily discuss the inevitability of temperature control.METHODS:In order to select the optimal temperature control method,the temperature change of the extraction liquid during the extraction using four temperature control methods was recorded:direct ultrasound,adding ice pack,adding ice water and cooling circulating water.In order to verify its reasonableness and validity,the applicable and representative soil active state component analysis standard material was selected as the experimental sample to determine the soil water-soluble fluorine content.To investigate the effect of temperature on the amount of water-soluble fluoride extracted from soil,the pH value of the extracted liquid was determined during the extraction process.RESULTS:The results showed that the cooling circulating water temperature control method could effectively control the extraction temperature within 25±2℃.The relative error(8.9%)was significantly less than that of direct ultrasound method(14.1%).The pH value of the extract liquid did not change significantly,and the determination results were stable and reliable.CONCLUSIONS:The temperature control method by cooling circulating water has the advantages of low cost,simple operation,accurate and reliable results,suitable for batch sample treatment,and can be widely used in soil environmental fluorine monitoring.