为了提高水体重金属LIBS检测的灵敏度以及降低元素检测限, 采用LIBS结合铝电极富集方法对水体中的重金属Pb, Cd, Ni进行了分析。 研究并优化了电极富集方法中关键参数—富集电压U, 分析了LIBS特征谱线的光谱强度与富集电压大小之间的关系, 得出重金属元素特征光强随着富集电压先增加后减小, 在1.2　V处光谱强度达到最大值, 选择了最优富集电压值为1.2　V。 研究了Pb, Cd, Ni三种重金属元素的光谱稳定性, 其特征谱线光谱强度的相对标准偏差(RSD)分别为5.98％, 4.25, ％和5.27％, 说明该实验方法得到的谱线具有较高的稳定性。 在0～ 0.13 mg·L-1范围内配制系列样品进行实验并对元素进行定量分析, 得到Pb, Cd, Ni三种重金属元素的检测限分别为1.2, 3.1和1.7 ppb。 结果表明: LIBS结合铝电极富集方法能够有效地提高特征谱线的稳定性以及降低元素的检测限, 为提高水体重金属LIBS的检测灵敏度和分析能力提供了方法支持。

In order to improve the detection sensitivity of laser-induced breakdown spectroscopy (LIBS) and lower the limit of the detection of elements, LIBS combined with Aluminum electrode enrichment method is adopted to analyze heavy metals such as Pb,Cdand Ni in the water. The relationship between the characteristic spectral intensity and the key parameters-voltage of electrode method is discussed, the spectral intensity increases first and then decreases with the increase of voltage. The spectral intensity reaches the maximum value when the enrichment voltage is 1.2 V while the optimal enrichment voltage value is 1.2 V. The stability of characteristic spectral lines of heavy metals is studied, and the relative standard deviation(RSD) of spectral intensity of Pb, Cd and Ni is 5.98％, 4.25 ％ and 5.27％ respectively, the result shows that the spectral line obtained by this method has high stability. A series of samples in the range of 0~0.13 mg·L-1 are prepared and quantitatively analyzed, the limit of detection of Pb, Cd and Ni is obtained 1.2, 3.1 and 1.7 ppb respectively. The above result shows that LIBS combined with aluminum electrode enrichment method can effectively improve the stability of characteristic spectral lines and lower the limit of detection of Pb,Cd and Ni. This research also provides a method to further improve detection sensitivity of LIBS and analysis ability of heavy metal in the water.