Determination of fluorine content in chemical fertilizer samples using the ultrasonic extraction-ion selective electrode method
LIU Bin1(), XU Jin-Li1(), DU Xue-Miao1, TANG Rui-Ling1, ZHANG Peng-Peng1, BAI Jin-Feng1, YU Lin-Song2, WAN Fang2
1. Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Sciences, Langfang 065000, China 2. Shandong Institute of Geophysical and Geochemical Exploration, Jinan 250013, China
As shown by the geochemical survey of national land quality, the land with excess fluorine in China covers an area of about 315 000 km2. As an element closely related to human health, fluorine has received wide attention and has been studied. Especially in recent years, the high-fluorine fertilizers used in agricultural activities have become a potential source of fluorine in soils. Moreover, the circulation and migration patterns of fluorine in soils, animals, and plants are yet to be further investigated. To prepare for a new round of national soil survey and modern health-related geological survey, it is necessary to develop a method to accurately determine the fluorine content in chemical fertilizers. Through experiments, this study compared four methods for sample decomposition, namely the extraction methods based on HCl boiling, NaOH molten water, and the Na2O2 molten water and the HCl ultrasonic extraction method at room temperature. The results show that the optimal method for sample pretreatment is to extract and decompose samples using ultrasound and HCl at room temperature, adjust the acidity using NaOH-H2SO4, and take sodium citrate as the ion buffering agent. Through investigation, the ultrasonic extraction time and temperature were determined to be 20 min and 20 ℃, respectively. The main quality parameters of the method were determined under the optimal sample pretreatment conditions, including the limit of detection of 1.63×10-6, the precision of 0.98%, and the recovery rate of 91%~108%. The results of this study show that the pretreatment of this method is simple, fast, and easy to operate. With the mode of establishing standard curves in sections, the quality parameters determined can fully meet the requirements for the analysis of chemical fertilizers.
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