Abstract：Water pollution has become one of the most serious environmental problems in the world nowadays. Improving the detection sensitivity in water pollution, minimizing the limit of detection, reducing the sample pretreatment procedures, and achieving in-situ analysis have become a focus of scientific research. In this paper, a new gelatin hydrogel curing method was presented, the concentration of Cu in CuSO4 solution was analyzed by laser-induced breakdown spectroscopy (LIBS) based on this method. A Nd∶YAG laser (output wavelength: 1 064 nm, pulse width: 8 ns) was used as the laser source. The gelatin was mixed with CuSO4 solution, and then the mixture was made into a gel-like solid by heating, stirring, aging, etc. Cu Ⅰ 324.7 nm and Cu Ⅰ 327.4 nm was selected as the analytical spectral lines. The optimal experimental conditions with 2.5% mass of gelatin CuSO4 solution were obtained by analyzing the relationship between the mass ratio of CuSO4 solution and the spectral intensity. Compared with the direct analysis method, the spectral intensity of Cu Ⅰ 324.7 nm and Cu Ⅰ 327.4 nm increased by 2.26 and 2.11 times, and the signal-to-back ratio was enhanced by 190.74 and 318.77 times, respectively. Under the optimal experimental conditions, gelatin gel samples of CuSO4 standard solutions with Cu2+ concentration of 8, 12, 16, 24, 48, and 64 mg·L-1 were prepared, the LIBS spectrum was obtained and analyzed on the 6 gelatin gel samples with the energy of 60 mJ/80 mJ/100 mJ, calibration curves of analytical lines were established. At the energy of 100, 80 and 60 mJ, the linear fitting coefficient R2 of Cu Ⅰ 324.7 nm are 0.999/0.989/0.984, and the limit of detection are 0.30, 0.66 and 6.37 mg·L-1, respectively; The linear fitting coefficient R2 of Cu Ⅰ 327.4 nm were 0.997/0.973/0.956, and the limit of detection were 0.45, 0.88 and 10.20 mg·L-1, respectively. The results show that the LIBS spectral intensity of the copper element in the CuSO4 solution can be enhanced with the gelatin hydrogel curing method. The LIBS sensitivity in water pollution can be improved effectively. The limit of detection can also be reduced significantly. The linear fitting coefficient R2 and the limit of detection at Cu Ⅰ 324.7 nm are better than those at Cu Ⅰ 327.4 nm. The linear fitting coefficient R2 and limit of detection increase with the laser energy enhancement. The linear fitting coefficient R2 with the calibration curve of Cu Ⅰ 324.7 nm was 0.999, and limit of detection was 0.30 mg·L-1 at 100 mJ, which reached the detection level of the enrichment method. The gelatin hydrogel curing method with simple sample preparation procedure and without contaminating elements, provides a new method for the application of LIBS technology in the detection of water pollution.
Key words：Laser-induced breakdown spectroscopy; Gelatin; Hydrogel curing; Limit of detection
李 倩，韩艳丽，宁日波，袁 备，王浩楠，徐送宁. 明胶水凝胶固化方法的水体中铜元素LIBS检测研究[J]. 光谱学与光谱分析, 2021, 41(05): 1537-1542.
LI Qian, HAN Yan-li, NING Ri-bo, YUAN Bei, WANG Hao-nan, XU Song-ning. LIBS Detection of Copper in Water Based on Gelatin Hydrogel Curing Method. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2021, 41(05): 1537-1542.
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