微波消解-离子色谱法测定磷矿石中氟和氯

磷矿石中氟和氯的准确测定对评价磷矿石的利用价值有重要指导作用。采用硝酸(1+1)和过氧化氢作为消解液,于160 ℃对样品微波消解15 min,将消解液通过0.22 μm在线超滤系统,采用Metrosep A Supp 5-250/4.0阴离子色谱柱,以3.2 mmol/L碳酸钠和1.0 mmol/L碳酸氢钠缓冲溶液作为淋洗液,电导检测器测定,建立了微波消解-离子色谱法测定磷矿石中氟和氯的方法。结果表明,氟的特征峰出现时间为6.29 min,氯的特征峰出现时间为9.17 min,氟和氯在质量浓度为10.00~50.00 mg/L范围内与其相应峰面积有良好的线性关系,线性相关系数均不小于0.999 6。氟和氯的方法检出限分别为0.102 μg/L和0.162 μg/L,定量限分别为0.343 μg/L和0.540 μg/L。按照实验方法对磷矿石标准物质中氟进行测定,并加入氟单元素标准储备溶液进行加标回收试验,结果表明,氟测定结果的相对标准偏差(RSD,n=7)小于1%;氟的测定结果与认定值相符合,回收率为98%~105%。将实验方法应用于6个磷矿石样品中氟和氯的测定,结果表明,实验方法测定结果的相对标准偏差(n=7)均小于1%;实验方法测定结果分别与GB/T 1872—1995中离子选择性电极法或GB/T 9729—2007中氯化银比浊法基本一致。

Determination of fluorine and chlorine in phosphate ore by ion chromatography with microwave digestion

The accurate determination of fluorine and chlorine has an important guidance to evaluate the utilization value of phosphate ores. The sample was treated by microwave digestion at 160 ℃ for 15 min using nitric acid (1+1) and hydrogen peroxide as the digestion solution. The digestion solution was filtrated with 0.22 μm on-line ultrafiltration system. The contents of fluorine and chlorine were determined by electrical conductivity detector using Metrosep A Supp 5-250/4.0 anion chromatography column. 3.2 mmol/L sodium carbonate and 1.0 mmol/L sodium bicarbonate buffer solution were selected as the eluent. The determination method of fluorine and chlorine in phosphate ore by ion chromatography with microwave digestion was established. The results showed that the occurrence time of characteristic peak of fluorine and chlorine was 6.29 min and 9.17 min, respectively. The mass concentration of fluorine and chlorine in range of 10.00-50.00 mg/L had good linear relationship with the corresponding peak area. The linear correlation coefficients were not less 0.999 6. The limits of detection for fluorine were 0.102 μg/L and 0.162 μg/L, and the limits of quantification were 0.343 μg/L and 0.540 μg/L, respectively. The certified reference materials of phosphate ore were determined according to the experimental method. Moreover, the standard stock solution of single fluorine was added for the recovery tests of standard addition. The relative standard deviations (RSD, n=7) of determination results of fluorine were less than 1%. The results showed that the found results of fluorine were in good agreement with the certified values, and the recoveries were between 98% and 105%. The proposed method was applied for the determination of fluorine and chlorine in six phosphate ore samples. The RSDs (n=7) of determination results were less than 1%. The results showed that the measured values were basically consistent with those obtained by ion selective electrode method in GB/T 1872-1995 or silver chloride turbidimetry in GB/T 9729-2007.