电位滴定法测定铁矿石中氧化亚铁
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摘要
铁矿石中氧化亚铁在检测过程中易被氧化,而采用电位滴定法测定时可直接在密闭容器中插入电极进行检测,从而避免亚铁离子被氧化,因此试验建立了电位滴定法测定铁矿石中氧化亚铁的方法。采用盐酸溶解样品,氟化铵加入量为0.5g使硅酸盐充分分解,样品分解时间为15min,无需加入硫磷混酸。以电位滴定法代替滴定法进行检测,对仪器工作条件进行了正交试验优化,设定滴定终点筛选标准(EPC)为20,最小加液量为20μL,信号漂移速率为50mV/min。实验方法用于测定4个铁矿石及岩石类标准样品中氧化亚铁,结果的相对标准偏差(RSD,n=10)不大于0.40%,测定值与认定值基本一致,相对误差(RE)不大于0.33%;分别按照实验方法和国标方法 GB/T 6730.8—2016测定9个铁矿石及岩石类标准样品中氧化亚铁,测定值与国标方法测定值相吻合。
The ferrous oxide in iron ore is easily oxidized during detection process.The determination by potentiometric titration can be conducted by directly inserting electrode into closed container,thus avoiding the oxidization of ferrous ions.Consequently the determination method of ferrous oxide in iron ore by potentiometric titration was established.The sample was dissolved with hydrochloric acid.0.5 g of ammonium fluoride was added to fully decompose the silicate.The resolving time of sample was 15 min.The addition of mixed sulfuric acid and phosphoric acid was not required.The titration method was replaced by potentiometric titration.The working conditions of instrument were optimized by orthogonal experiments.The equivalence point criterion(EPC)of potentiometric titration was 20,the minimum dosage of sample solution was 20μL,and the signal drift rate was 50 mV/min.The proposed method was applied for the determination of ferrous oxide in four standard samples of iron ore and rock.The relative standard deviations(RSD,n=10)of measured results were not more than 0.40%.The found results were basically consistent with the certified values.The relative errors(RE)were not more than 0.33%.The content of ferrous oxide in nine standard samples of iron ore and rock were determined according to the experimental method,and the found results were consistent with those obtained by national standard method(GB/T6730.8-2016).
The ferrous oxide in iron ore is easily oxidized during detection process.The determination by potentiometric titration can be conducted by directly inserting electrode into closed container,thus avoiding the oxidization of ferrous ions.Consequently the determination method of ferrous oxide in iron ore by potentiometric titration was established.The sample was dissolved with hydrochloric acid.0.5 g of ammonium fluoride was added to fully decompose the silicate.The resolving time of sample was 15 min.The addition of mixed sulfuric acid and phosphoric acid was not required.The titration method was replaced by potentiometric titration.The working conditions of instrument were optimized by orthogonal experiments.The equivalence point criterion(EPC)of potentiometric titration was 20,the minimum dosage of sample solution was 20μL,and the signal drift rate was 50 mV/min.The proposed method was applied for the determination of ferrous oxide in four standard samples of iron ore and rock.The relative standard deviations(RSD,n=10)of measured results were not more than 0.40%.The found results were basically consistent with the certified values.The relative errors(RE)were not more than 0.33%.The content of ferrous oxide in nine standard samples of iron ore and rock were determined according to the experimental method,and the found results were consistent with those obtained by national standard method(GB/T6730.8-2016).
引文
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[3]Fatemeh S,Taher M A.Application of a new water-soluble polyethylenimine polymer sorbent for simultaneous separation and preconcentration of trace amounts of copper and manganese and their determination by atomic absorption spectrophotometry[J].Analytica Chimica Acta,2006,565(2):152-156.
[4]胡艳巧,程文翠,支云川,等.四酸溶矿-电感耦合等离子体发射光谱法测定铬铁矿中多种元素[J].分析实验室,2016,35(11):1312-1316.HU Yan-qiao,CHENG Wen-cui,ZHI Yun-chuan,et al.Simultaneous determination of 11elements in chromites by inductively coupled plasma-atomic emission spectrometry with HCl-HNO3-HF-HClO4 digestion method[J].Chinese Journal of Analysis Laboratory,2016,35(11):1312-1316.
[5]陈贺海,鲍惠君,付冉冉.等.微波消解-电感耦合等离子体质谱法测定铁矿石中铬砷镉汞铅[J].岩矿测试,2012,31(2):234-240.CHEN He-hai,BAO Hui-jun,FU Ran-ran,et al.Determination of Cr,As,Cd,Hg and Pb in iron ores using inductively coupled plasma-mass spectrometry with microwave digestion[J].Rock and Mineral Analysis,2012,31(2):234-240.
[6]Zareba S,Szarwilo K,Pomykalski A.Determination of Fe(II)and Zn(II)by spectrophotometry,atomic absorption spectrometry and ions chromatography methods in Vitrum[J].II Farmaco,2005,60(5):459-464.
[7]Tzur D,Dosortzev V,Kiroma-Eisner E.Titration of low levels of Fe2+with electrogenerated Ce4+[J].Analytica Chimica Acta,1999,392(2/3):307-318.
[8]张明,刘子瑜.重铬酸钾滴定法测定铁矿石中亚铁含量[J].理化检验:化学分册(Physical Testing and Chemical Analysis Part B:Chemical Analysis),2013,49(12):1514-1516.
[9]陈占生,杨理勤,谢璐,等.重铬酸钾容量法测定铁矿石中全铁的方法改进[J].中国无机分析化学,2015,5(3):41-44.CHEN Zhan-sheng,YANG Li-qin,XIE Lu,et al.An improved method for potassium dichromate determination of total iron in iron ore[J].Chinese Journal of Inorganic Analytical Chemistry,2015,5(3):41-44.
[10]赵怀颖,温宏利,夏月莲,等.无汞重铬酸钾-自动电位滴定法准确测定矿石中的全铁含量[J].岩矿测试,2012,31(3):473-478.ZHAO Huai-ying,WEN Hong-li,XIA Yue-lian,et al.Accurate determination of total iron in ores by automatic potentiometric titration without potassium[J].Rock and Mineral Analysis,2012,31(3):473-478.
[11]阮建明,黄宝红,农海兰,等.自动电位滴定法与手动滴定法测定糕点中过氧化值的比较[J].现代农业科技,2017(14):262-263.RUAN Jian-ming,HUANG Bao-hong,NONG Hai-lan,et al.Comparison between automatic potentiometry and manual titration method in determining peroxide value[J].Modern Agricultural Science and Technology,2017(14):262-263.