火焰原子吸收光谱法测定钕铁硼磁铁中铅

Determination of lead in neodymium-iron-boron magnetic alloy by flame atomic absorption spectrometry

钕铁硼磁铁已在日用消费品中广泛使用,随着日用消费品环保质量要求的提高,也就产生了测定钕铁硼磁铁中的铅含量需求。采用王水溶样,于谱线Pb 283.3nm处,采用氘灯扣背景,以铁基体匹配法建立校准曲线,实现了空气-乙炔火焰原子吸收光谱法对钕铁硼磁铁中铅含量的测定。实验详细讨论了样品中主要基体元素钕、铁、硼对测定的影响。结果表明,样品中硼和钕对铅测定的影响可忽略;而铁基体对测定的干扰不可忽略。按照钕铁硼磁铁主体硬磁相结构式Nd_2Fe_(14)B估算出铁在磁铁中的大致质量分数为71%,据此,可推算出按照实验方法消解定容后样品溶液中铁的质量浓度约为2 840mg/L。试验表明铁的质量浓度在1 600~3 600mg/L范围内时铅的吸光度保持稳定,但相对于基体空白的吸光度均高出很多。因此,实验最终选择匹配2 800mg/L的铁来消除基体干扰。在选定的实验条件下,方法线性范围为0.10~5.00mg/L,相关系数为0.999,检出限为0.02mg/L。按照实验方法对3个钕铁硼磁铁实际样品中铅进行测定,平行测定6次结果的相对标准偏差(RSD)小于6%,回收率在93%~103%之间。根据日用消费品中铅限值要求,配制铅质量分数为1 000mg/kg的钕铁硼磁铁模拟样品并按实验方法进行分析,得到的结果与理论值基本一致。

The neodymium-iron-boron magnetic alloy has been widely used in goods for everyday consumption.With the increasing requirements of goods for everyday consumption in environmental quality,the determination of lead content in neodymium-iron-boron magnetic alloy was attracting attention.The sample was dissolved with aqua regia.The calibration curve was established by iron matrix matching method,and the background was deducted by deuterium lamp.Thus,a determination of lead content in neodymium-iron-boron magnetic alloy by air-acetylene flame atomic absorption spectrometry was realized at spectral line of Pb 283.3 nm.The effect of main matrix elements including neodymium,iron and boron in sample on determination of lead was systemically investigated.The results showed that the influence of boron and neodymium could be ignored.However,the interference of iron could not be neglected.According to the structural formula(Nd 2Fe 14 B)of main hard magnetic phase in neodymium-iron-boron magnetic alloy,the mass fraction of iron was approximately 71%.It could be calculated that the mass concentration of iron in sample solution was about 2 840 mg/L after the sample was digested and diluted to constant volume according to the experimental method.The experiments indicated that the absorbance of lead were stable when the mass concentration of iron was in range of 1 600-3 600 mg/L,while,they were much higher than that of matrix blank.Therefore,the matrix interference was finally eliminated by matching 2 800 mg/L of iron.Under the selected experimental conditions,the linear range of method was 0.10-5.00 mg/L,the correlation coefficient was 0.999,and the detection limit was 0.02 mg/L.The content of lead in three neodymium-iron-boron magnetic alloy actual samples was determined according to the experimental method.The relative standard deviation(RSD,n=6)was less than 6%,and the recoveries were between 93%and 103%.According to the limit requirement of lead in goods for everyday consumption,the simulated sample of neodymium-iron-boron magnetic alloy with lead content of 1 000 mg/kg was prepared and determined by the proposed method.The results were basically consistent with the theoretical values.