激光烧蚀ICP-AES中蒸发物输送过程研究

利用Nd:YAG纳秒脉冲激光器烧蚀土壤标样,由氩气作为载气将激光蒸发物质输送到ICP光源,用光电检测法记录元素As、Pb、Cr、Hg和Cd的光谱强度。通过改变炬管与样品蒸发室之间传输管的长度、内径以及载气流量的大小来测量比较重金属元素的光谱强度、信背比和相对标准偏差的变化,以研究激光蒸发物的输送过程对ICP发射光谱的影响。测量结果显示:在传输管长度为60cm,内径为4mm时光谱强度和信背比为最佳;输送激光蒸发物质的载气流量为0.4L/min时,光谱强度和信背比最好;当载气流量保持在0.4L/min不变时,使用内径为4mm的传输管得到的As、Pb、Cr、Hg和Cd分析信号的相对标准偏差(RSD)分别是4.53%,9.08%,7.56%,4.42%和4.24%,而当传输管内径为5.5mm时,其RSD分别是9.72%,9.93%,9.76%,7.07%和7.18%。研究表明,传输管长度尽可能短并且内径合适是提高光谱质量和测量精度的重要条件。

Study of Transmitting Process of Evaporation Materials in the Laser Ablation ICP-AES

The nanosecond pulse laser of Nd：YAG was used to ablate the soil standard samples.The ablated material was introduced to inductively coupled plasma（ICP）source by the argon carrier gas.The spectrum intensities of the elements including As,Pb,Cr,Hg and Cd were collected through the photoelectric detection method.In order to investigate the influence of the transmission process of the materials evaporated by laser on the emission spectrum of the ICP,the changes of the spectrum intensity,signal-to-background ratio,and relative standard deviation of the heavy metal elements were measured and compared by changing the length,the diameter,and the carrier gas flow of the transmission tubes between the torch and the sample evaporation chamber.The measurement results showed that the spectrum intensity and the signal-to-background ratio are the best when the transmission tube length is 60cm,diameter is 4mm;the spectrum intensity and signal-to-background ratio are the best when the carrier gas flow transporting the materials evaporated by laser is 0.4L/ min;when the carrier gas flow was constant at 0.4L/min,the relative standard deviation（RSD）of the analyzed signal of As,Pb,Cr,Hg,and Cd were 4.53%,9.08%,7.56%,4.42%,and 4.24%respectively by using 4mm diameter transmission tube,while the diameter of transmission tube is 5.5mm,the RSD were 9.72%,9.93%,9.76%,7.07%,and 7.18%,respectively.The studies showed that the shortest possible transmission tube length and suitable diameter are important conditions to improve the spectral quality and measurement accuracy.