Determination Of Heavy Metals In Aquatic Products By LIBS

With industrialization and urbanization,a large number of toxic heavy metals are discharged into rivers,lakes and oceans.The increasing pollution of toxic heavy metals in aquatic products has become a serious problem in the world.Therefore,it is of great significance to carry out the heavy metal elements detection and improve the detection ability of heavy metal pollution in aquatic products for the safety assessment of aquatic products and the protection of consumer safety.Laser induced breakdown spectroscopy(LIBS)is an emerging detection technology in the field of food analysis,which has the advantages of fast,accurate and free from contamination.It has been used in the field of material element detection.Because the sample only needs simple pretreatment or no pretreatment,LIBS can carry out continuous,multi-element,qualitative and quantitative on-site rapid analysis,and has the potential as a meat industry monitoring technique.Therefore,it is necessary to develop LIBS technology to detect heavy metals in aquatic products.As the repeatability and stability of single pulse(SP)LIBS detection is poor,and it is easy to be affected by the external environment,the detection sensitivity of SP-LIBS is generally low.In contrast,the double pulse(DP)LIBS technology can often obtain higher detection sensitivity.In this study,both SP-LIBS and DP-LIBS were used to detect the content of heavy metals in aquatic product samples.Cadmium(Cd)contaminated Tilapia mossambica was used as the example of aquatic products,and the Tilapia mossambica samples were prepared by several different sample pretreatment methods.The specific methods and technologies with high detection sensitivity for heavy metal pollutants in aquatic products were obtained by comparison these results.The main contents are as follows:1.Based on the fresh tilapia meat polluted by heavy metal elements Cd,five different sample series were prepared,including fresh slicing,fresh crushing,frozen slicing,frozen crushing and dry pressing,and each sample series had a series of samples with different heavy metal concentrations.2.SP-LIBS technology was used for qualitative and quantitative detection of heavy metal elements in five series samples.The experimental parameters such as spectrum collection time delay,pulse laser energy and focus position were optimized.The characteristic line intensity,stability in terms of relative standard deviation(RSD)and signal-to-noise ratio(SNR)of heavy metal elements in SP-LIBS spectra of five series samples were studied,as well as the relationship between line intensity and concentration.The results showed that the SP-LIBS spectra of frozen crushing and dry pressing samples were helpful to improve the detecting sensitivity of heavy metal pollution in aquatic products.3.Collinear DP-LIBS technology was used to study the qualitative and quantitative detection of heavy metals in five series samples.The experimental parameters of double pulse time delay,two pulse laser energy and energy ratio were optimized,and the effects of sample preparation methods on the optimal double pulse time delay were studied as well.The effects of different sample preparation methods on the spectral intensity,RSD and SNR of Cd II 214.44 nm line were discussed.4.The relationship between the characteristic Cd ? 214.44 nm line intensity and the concentration of element Cd was studied.The calibration curve of single variable linear regression was established based on the relationship between the line intensity and the concentration.The effects of SP and DP LIBS technology and five sample preparation methods on the detection sensitivity were compared and discussed.