ICP-MS测量环境样品中铀的非质谱干扰内标校正研究

内标的合理应用直接关系到测量结果的可靠性,通过外标与内标校正相结合的方法,实验研究了Y,Rh,In,Tb,Yb,Tl,Bi,Re作为内标对ICP-MS测量铀的非质谱干扰的校正效果。对于非抑制/增强基体效应,各内标元素校正结果明显优于无内标校正结果,高质量数内标元素Tb,Yb,Re,Tl,Bi可获得较好的校正效果,校正偏差优于5%,其中以Tl为最佳;对于盐度较高的样品溶液,由于基体对待测元素和内标元素产生了明显不同的抑制/增强效应,因此各内标校正结果均不理想,这表明内标对可溶性固体引起的抑制/增强效应的校正能力有限。在铀的测量中,对于含盐度在300～500μg/mL的样品,内标校正造成的偏差可达到5%～10%;对于盐度在500μg/mL以上的样品,内标校正造成的偏差很可能超过10%或者更高。

Study on correction of matrix effect with different internal standards during measurement of uranium by ICP-MS

The study on correction of matrix effect with different internal standards during measurement of uranium by ICP-MS was performed using the method of external calibration with internal standards.It was found that signal shift aroused by matrix effect of non suppression-enhancement could be corrected well by the internal standards,such as Tb,Yb,Re,Tl,Bi,because of their close match in mass and ionization potential with uranium,in which Tl appeared to be best.It is difficult to correct matrix effect of suppression-enhancement produced by heavy matrix just using internal standards,because degree of suppression-enhancement aroused by matrices is very different between measured element and internal standard elements.The deviation caused by internal standard calibration can reach 5% to 10% for samples with the salinity in 300 ～ 500 μg/mL,and for samples with the salinity more than 500 μg/mL the deviation is likely to exceed 10% or higher.So it is better to dilute the sample with high total dissolved solids before measurement by ICP-MS in order to lighten suppression-enhancement effect.