为了改变水溶液的物理性质, 提高ICP发射光谱的辐射强度, 实验采用波长为976 nm的近红外激光和10.6 μm的CO2激光正交辐照水溶液, 研究了不同激光功率密度和辐照时间对水溶液表面张力和粘度的影响, 也探讨了处理后水溶液对ICP光谱强度的增强作用。实验结果表明, 在976 nm激光功率密度为0.265 7 W·cm-2, CO2激光为0.2069 W·cm-2以及辐照时间为40 min条件下, 水溶液的表面张力和粘度比未进行激光处理时的分别减小了42.13%和14.03%, 而雾化效率升高了51.26%。将优化条件下激光处理的水溶液引入ICP光源后发现, 样品元素As, Cd, Cr, Hg和Pb的光谱强度比水溶液未处理时的分别提高了46.29%, 94.65%, 30.76%, 33.07%和94.58%, 信背比分别增大了43.84%, 85.35%, 28.71%, 34.37%和90.91%;等离子体温度和电子密度也分别升高了5.94%和1.18%。可见, 双光束激光正交辐照水溶液的方法能够明显降低水溶液的表面张力和粘度, 提高ICP光源的辐射强度, 这为顺利检测水样品中痕量重金属元素创造了条件。

In order to change the physical properties of aqueous solution and improve the radiation intensity of the ICP emission spectrum, the effects of different laser power density and irradiation time on the surface tension and viscosity of aqueous solution were investigated by using near infrared laser at 976 nm and CO2 laser at 10.6 μm to irradiate aqueous solution orthogonally, then the enhancement of ICP spectral intensity with processed solution was discussed. The results showed that the surface tension and viscosity of aqueous solution reduced by 42.13% and 14.03% compared with the untreated, and the atomization efficiency increased by 51.26% at the laser power density 0.265 7 W·cm-2 of 976 nm and 0.206 9 W·cm-2 of CO2 laser with 40 min irradiation time. With the optimized aqueous solution introduced into the ICP source, the spectral line intensity of sample elements As, Cd, Cr, Hg and Pb was enhanced by 46.29%, 94.65%, 30.76%, 33.07% and 94.58% compared to the untreated aqueous solution, while the signal-to-background ratio increased by 43.84%, 85.35%, 28.71%, 34.37% and 90.91%, respectively. Plasma temperature and electron density also increased by 5.94% and 1.18% respectively. It is obvious that the method of double-beam laser orthogonal irradiation on solution can reduce the surface tension and viscosity of aqueous solution significantly, and raise the radiation intensity of ICP source, and will provide a better condition for detecting the trace heavy metal elements in water samples.