电感耦合等离子体质谱(ICP-MS)法测定钒钛磁铁矿中稀土元素

Determination of Rare Earth Elements in Vanadium Titanomagnetite by Inductively Coupled Plasma Mass Spectrometry(ICP-MS)

研究钒钛磁铁矿中的稀土元素特征可以判断岩石成因与岩浆作用等,因此准确测定稀土元素的含量显得尤为重要。由于钒钛磁铁矿为难溶矿物,不易分解,因此常规的酸溶很难将钒钛磁铁矿中的稀土元素分解完全。通过比较四酸(盐酸-硝酸-氢氟酸-高氯酸)和五酸(盐酸-硝酸-氢氟酸-高氯酸-硫酸)的开放酸溶以及氢氧化钠-过氧化钠碱熔三种样品预处理方式,结果表明,四酸与五酸不能完全分解钒钛磁铁矿,导致15种稀土元素除了钇元素外均有不同程度偏低,进行X射线衍射测定发现,四酸溶解后生成的不溶物主要为硫酸氧钒,五酸溶解后生成的不溶物主要为硫酸钙,因此建立了氢氧化钠-过氧化钠碱熔-电感耦合等离子体质谱(ICP-MS)法测定钒钛磁铁矿中15种稀土元素的方法。为了减少轻稀土对重稀土以及钡的氧化物或氢氧化物对^(153)Eu等元素的质谱干扰,建立了合理的干扰校正方程,干扰量进行了有效扣除。方法检出限为0.006~0.21μg/g,相对标准偏差(RSD,n=12)为1.5%~7.2%,加标回收率为100%~108%,证明方法可用于钒钛磁铁矿中稀土元素的分析。对承德不同地区钒钛磁铁矿进行稀土配分模式分析,可以得出右倾斜轻稀土富集,三个地区稀土配分模式曲线相似,它们之间具有较大的亲缘关系,物源相似。

The characteristics of rare earth elements in vanadium-titanium magnetite can be used to determine the genesis and magmatism of rocks,so it is particularly important to accurately determine the content of rare earth elements.Because vanadium titanomagnetite is an insoluble mineral,it is difficult to decompose the rare earth elements in vanadium titanomagnetite completely by the conventional acid dissolution.Compared with three sample pretreatment methods,namely,open acid dissolution of tetracarboxylic acid(hydrochloric acid-nitric acid-hydrofluoric acid-perchloric acid),pentacarboxylic acid(hydrochloric acid-nitric acid-hydrofluoric acid-perchloric acid-sulfuric acid),and alkali melting of sodium hydroxide-sodium peroxide,the results showed that tetracarboxylic acid and pentacarboxylic acid could not completely decompose vanadic titanomagnetite,which led to low levels of 15 rare earth elements except yttrium.X-ray diffraction analysis showed that the undissolved tetracarboxylic acid was insoluble.Calcium sulfate was the main insoluble substance produced after the dissolution of pentanoic acid,so a method for determination of 15 rare elements in vanadium titanomagnetite by sodium hydroxide-sodium peroxide alkali fusion-inductively coupled plasma mass spectrometry(ICP-MS)was established.In order to reduce the interference of light rare earth to heavy rare earth and barium oxide or hydroxide to ^(153)Eu and other elements,a reasonable interference correction equation was formed and the interference amount was effectively deducted.The detection limit of the method was 0.006—0.21μg/g,the relative standard deviation(RSD,n=12)was 1.5%—7.2%,and the recovery rate was 100%—108%,which proved that the method could be used for the analysis of rare earth elements in vanadium-titanium magnetite.By analyzing the REE distribution patterns of vanadium-titanium magnetite in different areas of Chengde,it was concluded that the right-dip light rare earth was enriched,and the REE distribution patterns in the three areas were similar,and there was a large kinship relationship between them and similar provenance.