内定标法水中Cr元素LIBS定量分析

Quantitative analysis of Cr in water by LIBS based on internal calibration method

以提高激光诱导击穿光谱(LIBS)技术精准检测水体中的重金属元素Cr为研究目的,对实验室配制的7种不同质量浓度的含铬(Cr)水溶液采用护肤棉进行富集,并对自然晾干后的护肤棉进行LIBS试验。首先对试验参数进行了优化并确定425.43 nm为Cr的特征分析谱线。选择护肤棉中固有的钙(Ca)元素作为内定标元素,其特征谱线为422.67 nm。分别采用内定标法和直接定标法进行定量分析,取其中的五个样品建立定量分析模型,并利用另外的两个样品验证模型的准确性,得出拟合曲线的线性相关系数分别为0.99614、0.73655,两个验证样品的相对误差值分别为11.38%、4.84%和64.66%、11.58%;内定标法LIBS的检出限为5.27μg/m L,优于之前滤纸富集的6.06μg/m L。试验结果表明以护肤棉为吸附基质结合内定标法能提高LIBS检测水体Cr元素的准确性、并能降低检出限。

In order to improve detection accuracy of heavy metal Cr in water by the laser induced breakdown spectros- copy （LIBS） ,7 kinds of different concentrations of chromium （Cr） water solution were prepared and enriched by the skin cotton, and then the cotton after drying was detected by LIBS. The experimental parametem were optimized, and 425.43 nm was determined as the Cr feature analysis spectral line. The natural calcium （Ca） element in the skin care cotton was chosen as internal calibration element, its feature spectral line is 422.67 nm. Internal calibration method and calibration method were used for quantitative analysis, and the quantitative analysis model was established for five samples, and then the another two samples were used to verify the accuracy of the model. The obtained linear correlation coefficients of the fitting curve are 0.99614 and 0.73655 respectively, and the relative errors of two valida- ted samples are 11.38% ,4.84% and 64.66%, 11.58% ;LIBS detection limit is 5.27 μg/mL by internal calibration method,and it is better than detection limit 6.06 μg/mL by filter paper enrichment. Experimental results show that the skin cotton as adsorption matrix combined with internal calibration method can improve the accuracy of LIBS in detecting Cr elements in water, and can reduce the detection limit.