Studies On Novelty Spectroscopic Techniques Of Sensitive And Rapid Analysis Of Sample Elements Aiming For Different Purposes

Highly sensitive and rapid elemental analysis of matters has significant scientific meanings and great application values for the development of modern science and technology.As a new type of analytical technique on the matter elements,laser-induced breakdown spectroscopy（LIBS）has attracted much attention due to its advantages of rapid,remote and online analysis.However,due to the inherent properties of LIBS,the analytical sensitivity of LIBS is relatively lower than that of traditional analytical methods.Therefore,improving the analytical sensitivity of LIBS has been becoming an important scientific problem in the development of LIBS.In addition,in different applications,there are different requirements on the instrument dimension,convenience of the analysis,and sample damage.According to different requirements,three novelty LIBS-related spectroscopic techniques have been developed and applied to realize highly sensitive and rapid elemental analysis in this thesis.In order to realize movable,highly sensitive and rapid alloy elemental analysis,high repetition rate laser-ablation spark-induced breakdown spectroscopy（HRR LA-SIBS）technique based on a fiber laser was developed.At a repetition rate of 30 k Hz,the characteristics of spark discharge and the optimal experimental condition have been investigated.Lead,iron,and aluminum elements in copper alloy samples were quantitatively analyzed while using an optical fiber spectrometer.By selecting Pb I 368.35 nm,Fe I 358.12nm,and A l I 396.15 nm as analytical lines,the detection limit of lead,iron,and aluminum in copper alloy was determined to be 240,113,and 30 ppm,respectively.It is 3-9 times better than that of determined without spark discharge assistance.The HRR LA-SIBS developed here based on fiber laser has a compact system dimension;it is possible to provide a movable,highly sensitive and rapid elemental analysis in the metallurgical industry.In order to realize highly sensitive and rapid analysis of trace toxic heavy metals in Chinese medicine herbs,an analytical system based on laser-induced breakdown spectroscopy combined with laser-induced fluorescence（LIBS-LIF）was built.As an analytical example,trace lead in rheum officinale was directly analyzed with LIBS-LIF under high detection sensitivity after pulverizing and pressing the original sample to pellets.The detection limit of lead was 0.13 ppm,far below 10 ppm,the limit of lead in medicinal herbs allowed by the WHO.It was demonstrated that the analytical sensitivity of LIBS-LIF could be improved by 2orders if compared with LIBS.Through this investigation,a practical technique has been successfully explored to realize highly sensitive and direct trace element analysis of medicinal herbs or other traditional Chinese medicines,which is very important for the development of traditional Chinese medicine in China.In order to realize sensitive elemental analysis of solid samples under micro-ablation,target-enhanced orthogonal double-pulse LIBS（TEODP-LIBS）technique was developed.In this technique,the signal intensities of the sample elements are significantly enhanced by introducing a solid target in the orthogonal double-pulse LIBS（ODP-LIBS）to improve the conversion efficiency of the reheating laser pulse energy and the introduction of additional collision mechanisms.Using aluminum as a solid target,the plasma characteristics were compared in the case of using or without using targets.Copper and lead elements in the water samples were analyzed with TEODP-LIBS combined with a matrix-conversion method.Compared with the traditional ODP-LIBS,the detection limits of copper and lead obtained by TEODP-LIBS can be 4.5 and 3.8 times better,respectively.When analyzing brass sample under very low ablation laser energy.2-3 orders or even higher signal enhancement factor could be obtained,demonstrating the potentials of using this technique to give sensitive elemental analysis under micro-ablation.In order to reduce the spectral interference of metal targets,KHCO₃ was first selected as the target material in TEODP-LIBS to achieve signal enhancement.Quantitative analysis of copper and chromium in aluminum alloy was carried out.The detection limits were improved by 5.1 and 8.8 times if compared with ODP-LIBS.Meanwhile,in order to help understand the physical mechanism of target enhancement,the plasma temperature,electron density,threshold of laser-ablation,sound intensity of the shock wave reflected by the target,and the signal enhancement factor were also studied in detail using KHCO₃,NH₄HCO₃,KH₂PO₄ and NH₄H₂PO₄ targets.It is found that among the four targets,the KHCO₃ target has the best signal enhancement effect.Finally,bismuth and tin in bismuth brass were also quantitatively analyzed.The TEODP-LIBS technique established in this work has potential applications in the highly sensitive element analysis of solid samples under micro-ablation as well as high resolution mapping analysis of surface element distribution.In conclusion,the HRR LA-SIBS,LIBS-LIF and TEODP-LIBS techniques developed or applied in this thesis meet the requirements for highly sensitive analysis of sample elements in different applications very well.They will have good scientific meanings and potential applications in the fields of metallurgical industry,biomedicine,sciences of new material and new energy,environmental monitoring,jewelry analysis,archaeology and so on.