Laser-Induced Breakdown Spectroscopy Detection of Cu Element in Pig Fodder by Combining Cavity-Confinement

In recent years, the problem of excessive heavy metals in pig fodder has been repeatedly banned, which has seriously endangered the health of people who eat pork and the environment's safety. The dry ashing-Atomic Absorption Spectroscopy as the national standard text method faces problems such as being time-consuming, sample destruction, and environmental pollution caused by reagents. Laser-induced breakdown spectroscopy (LIBS) is known as the "future superstar" in chemical analysis for its fast, nearly non-destructive, and no need for complex sample preparation. Traditional LIBS technology has the disadvantages of weak characteristic spectrum intensity and low detection accuracy when applied to pig fodder safety and quality inspection. In response to this defect, it is proposed to combine LIBS technology with cavity-confinement and use the cavity-confinement method to improve the intensity of the analysis spectrum. In this way, the detection of lower concentration samples and the rapid green detection of Cu element content in pig fodder samples are realized. Take Cu I 324. 75 nm as the analysis line, under the optimized energy, it compares the influence of loading cylindrical cavity-confinement cavity with different heights and diameters under different delay times on the analysis line. Then it selects cavity-confinement cavity which has perfect overall enhancement effect of the analysis line to collect the LIBS spectrum of 7 groups of pig fodder samples with different concentrations. Then the sensitivity of the LIBS system was analyzed in combination with the reference concentrations of Cu elements in seven groups of pig feed samples obtained using national standard methods. The results show that loading the cavity-confinement cavity causes enhancement of the analyzed spectral lines' intensity without significantly affect for the background spectrum. Under the maximum enhancement factor of the analysis spectral line intensity is 5. 16, the diameter of the cavity-confinement cavity is 5. 0 mm, and the height is 2. 0 mm. The overall enhancement effect on the analysis spectrum is the best. Based on those mentioned above best experimental parameters, the pig fodder was quantitatively analyzed by the characteristic spectral peak intensity of Cu element at 324. 75 nm. The results showed that the linear relationship between the concentration of Cu element in pig fodder samples and the intensity of the analysis spectrum under different concentrations after loading the space confinement cavity was significantly improved compared with the traditional LIBS. The univariate calibration model R-2 was increased from 0. 742 to 0. 996, and the detection limit fell from 6. 21 to 1. 61 mg " kg(1) (the recommended content of Cu elemental diet in pigs in the Guidelines for Safe Use of Fodder Addition is 3 similar to 6 mg " kg(1)), and the detection sensitivity is increased by 2. 86 times. Studies have shown that the combination of space limitation and LIBS technology can greatly improve the detection accuracy and sensitivity of the system, and reduce the detection limit of the element to be measured below the national requirements. Moreover, it also provides support for the realizing rapid green detection of LIBS for samples with low Cu element content in pig fodder.