Effect of cavity-confinement and microwave-assistance on the sensitivity of LIBS for detecting Cu content in pig feed

The laser-induced breakdown spectroscopy (LIBS) is a potential tool for detecting heavy metals in pig feed. In order to implement a highly sensitive LIBS system required for the detection of Copper in pig feed and achieve better detection results, this work combines cavity-confinement and microwave-assistance with the LIBS system. Based on the characteristic spectral intensity of Cu I 324.75 nm, four factors including delay time, laser energy, cavity-confinement diameter, and microwave-assisted power are optimized by using single factor method and response surface methodology (RSM) for obtaining suitable experimental parameters and detection performance. The detection results show that as compared with the single factor method, the optimal experimental parameters obtained by using RSM increase the intensity of the characteristic spectral lines by 21.69% and the detection limit is as low as 0.878 mg/kg. As compared with the traditional LIBS techniques, the use of cavity-confinement combined with microwave-assistance increase the detection sensitivity of LIBS technique by 18.6-fold. The results show that RSM effectively analyzes the interactions between factors and their effects on the response values to effectively obtain better values for each factor. This enhances the LIBS spectra by cavityconfinement and microwave-assistance, and improves the sensitivity of detection of Cu in the pig feeds, which is suitable for realizing the quantitative detection of low concentration elements in pig feeds.