Research of Isotopic Reference Material for Improvement of Measurement Precision of Isotopic Ratios in Space and Earth Sciences

钕同位素标准要求低杂质。此外，(1)由于日本普遍研究的岛弧样品具有较高的^<143>Nd/^<144>Nd比值；(2)由于减少了^<142>Ce和^<144>Sm等压干扰，因此稀土杂质含量应较低。对SPEC、JMC、CERAC、MERCK、ShinEtsu和Mitsuwa六家化工公司制备的高纯氧化钕进行了同位素比和稀土杂质的检测。最好选用新越公司的试剂。从ShinEtsu公司购买的两瓶氧化钕试剂各1kg，定义为拆分1和拆分2。拆分1的上部被丢弃。其余的分成725个小瓶，每个小瓶装1g试剂，从上端（位置1）到下端（位置725）依次。在11个研究所的12台质谱仪上，采用特定的工艺循环测定了JNdi-1和LaJolla-Nd的同位素比值，除使用归一化值外，其余的步骤分别为<@D1143@>D1Nd/<@D1144@>D1Nd=0.7219.18个位置，分别测量了2 ~ 12次。循环测量的jNdi-1和LaJolla-Nd分别定义为A和B， F （Factor）值由这两个值计算，F<@D2n@>D2=2A<@D2n@>D2/(B<@D2n@>D2+B<@D2n+1@>D2)。同一研究所同一仪器、同一程序测得的几个位置的F值在其标准差（2sigma）范围内是一致的。因此，1kg瓶中试剂的同位素组成被认为是均匀的。这允许计算所有18个位置的F值的平均值，即1.000503(]SY.+-。() 1 (1 sigmam)。与LaJolla-Nd的0.511857对应的JNdi-1同位素比值为0.512114(]SY.+- .[)7。此外，为了考虑标准对<@D1146@>D1Sm（即绝灭核素）衰变产生的<@D1142@>D1Nd变化的作用，还检查了JNdi-1的<@D1142@>D1Nd/<@D1144@>D1Nd比值。从104个数据的结果中发现，F值的平均值为1.000006(]SY.+-。() 3 (1 sigmam)。这说明JNdi-1和LaJolla-Nd的值没有显著差异。日本地质调查局已经开始分配新的同位素标准试剂（JNdi-1）。少

Neodymium isotopic standard requires low impurity. In addition, (1) it should have a high ^<143>Nd/^<144>Nd ratio because of high ratios in island-arc samples generally researched in Japan and (2) should have low rare-earth impurities because of the reduction of isobaric interference by ^<142>Ce and ^<144>Sm. Isotopic ratios and rare-earth impurities were examined in high purity neodymium oxides prepared by six chemical companies, SPEC,JMC,CERAC,MERCK,ShinEtsu and Mitsuwa. The reagent of the ShinEtsu company is preferable. Two bottles of 1kg each, of neodymium oxide reagent from the same lot, were bought from the ShinEtsu company and defined as split 1 and split 2. Upper part of split 1 was discarded. The rest was divided into 725 small bottles, each of them containing 1g reagent, from upper part (position 1) to lower part (position 725) in order.Isotopic ratios of JNdi-1 and LaJolla-Nd were determined by cyclic measurement on 12 mass spectrometers in 11 institutes using specific proce … More dures, except for the using of normalized value, <@D1143@>D1Nd/<@D1144@>D1Nd=0.7219.18 positions of JNdi-l were measured twice to twelve times, respectively. The values of jNdi-1 and LaJolla-Nd by cyclic measurement are defined as A and B,respectively, and F (Factor) vaoues are calculated from the two values, F<@D2n@>D2=2A<@D2n@>D2/(B<@D2n@>D2+B<@D2n+1@>D2). F values of several positions measured by the same instrument and the same procedure in one institute are consistent in the range of their standard deviation (2sigmam). Therefore, the isotopic composition of the reagent in the 1kg bottle is considered to be homogenous. This allows to calculate an average of F values of all 18 positions, that is 1.000503(]SY.+-。[)1 (1sigmam). The isotopic ratio of JNdi-1 which corresponds to 0.511857 of LaJolla-Nd is 0.512114(]SY.+-。[)7. Moreover, to consider the role of standard for variation of <@D1142@>D1Nd produced by decay of <@D1146@>D1Sm, that is the extinct nuclide, <@D1142@>D1Nd/<@D1144@>D1Nd ratios of JNdi-1 were also checked. From the results of the 104 data, it is found that the average of F values is 1.000006(]SY.+-。[)3 (1sigmam). This indicates that the values of JNdi-1 and LaJolla-Nd do not have a significant difference. Geological Survey of Japan has started to distribute the new isotopic standard regent (JNdi-1). Less