Study On Detection Method And Quantitative Analysis Of Metal Elements Based On LIBS

Application of Laser induced Breakdown Spectroscopy has been expanded,from steel production line and coal production line to agricultural products,Water quality,soil and industrial pollutants.In this paper,two methods of quantitative measurement of the metal elements in glass,leather and rice by using laser-induced breakdown spectroscopy?LIBS?were established.The LIBS system is composed of a Q pulse Nd:YAG laser,an echelle grating spectrometer,an ICCD detector and innovative rotating sample stage.We collected the LIBS spectra of three different samples by selecting characteristic lines of mental elements and optimizing the laser energy,delay time and depth of focus.Free calibration method and intensity concentration calibration method were used to quantitatively analyze the content of heavy metals especailly in leather and rice samples after obtaining spectral information,which further broadening the application of LIBS in textile industry and agricultural product field.1.Detection of Si and Ba in glass sampleThe LIBS spectral detection scheme was established with four kinds of standard glass samples provided by QC.According to the NIST atomic database of USA,the characteristic spectral lines of Si and Ba elements are established,and the experimental conditions affecting the spectral intensity are optimized,including laser energy,delay time,focal depth.They were 150mJ,0.5?s and 2mm respectively.2.Detection of Pb and Cr in leather sampleThe experimental device was optimized.A new rotating sample stage device was designed to solve the problem that the low power laser can not excite the atomic spectrum because of soft and thin texture.And the problem that high-power laser was easy to puncture the sample before the excitation of the atomic spectrum was also solved.The experimental conditions were optimized after analyzing the spectra of 30leather samples.We chose laser energy of 125mJ,delay time of 2?s,focal depth of1mm as best optimum conditions.The Boltzmann curves of the main elements Pb and Cr were established by using free calibration method.According to these curves,the contents of Pb and Cr in leather samples were calculated.The relative standard deviation of the contents of Pb and Cr ranged from 3.22%to 7.66%and from 12.19%to 14.00%respectively.T test results showed that there was no significant difference between the measured values and the actual values.3.Detection of Cd in rice sampleTwo cadmium supplementation schemes were established.The fist method was using soil added by Cd to cultivate the rice sample and deteceting the content of Cd in the roots,stems,leaves,nodes and spikes of rice.Because of the limited ability of rice samples to absorb heavy metal Cd,the content of Cd was less than the detection limit of LIBS spectrometer.The another method was using 5 different concentrations of CdCl₂ solution with a gradient of 200,400,600,800 and 1000?g/g to soak the rice sample.And then the LIBS spectra of Cd in 346.62nm,361.05nm and 340.46 nm were obtained.The best conditions of laser energy and delay time were 120mJ and 1.7?s.Quantitative analysis modelss of intensity concentration were established including the quadratic linear regression model and univariate linear regression model.The fitting error ranges were 0.67%to 7.3%,9.6%to 16.9%respectively,which effectively verified the feasibility of quantitative determination of heavy metals in rice by LIBS.