Investigation Of Laser Ablation Solid Sampling Method For Icp Source

With laser technology, in particular the rapid development of pulsed laser technology, laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES) has been widely used in environmental science, material science, life science, geological analysis, metallurgy analysis, and other fields. This method is after the laser beam at the high energy density was focused and acted on the surface of sample by the lens, the substance of sample surface was evaporated or gasified, the sample formed steam and tiny particles were transported by argon carrier gas, then atomizated and ionizated in the ICP source. In order to reduce the detection limit of the spectral analysis, to get more precise and reliable analytical results, the experimental conditions of the approach were optimized from the various angles in this paper. The main means were used as follows:First, the influence of the parameters indicator of the transfer tubes and the carrier gas flow rate on the spectral intensity and the signal-to-background ratio of the elements in the samples were studied. The best transport conditions were obtained for the ablated samples. The experimental results showed that when the soil standard sample and steel standard sample were ablated by the pulsed laser, the optimization conditions in the transport processes of the ablated material to the ICP were the 60cm-length, 4mm diameter transfer tube, the 0.4 and 0.5L/min flow rate of the argon carrier gas, respectively. The right carrier gas flow rate is related to the sample properties.Second, the influence of the output energy of the pulsed laser on the spectral line intensity, the signal-to-background ratio, the ablated particles size, the full-width at half-maximum were studied. The experimental results showed that with the increase of the laser output energy, the sample particles size by laser ablation were not significantly changed, the sample quantity evaporated is markedly improved, the data of the spectral intensity and signal-to-background ratio were enhanced markedly, the full-width at half-maximum was increased at first and then reduced. In order to study the atomization and excitation mechanism of the inductively coupled plasma source, the excitation temperature and electron density of the sources were determined in the different conditions of the putout energy. The experimental results showed that with the increase of the laser output energy, the excitation temperatures were gradually decreased. At the certain condition of laser output energy, with the increase of the observation height of the ICP the electron density was basically increased at first and then decreased.Third, the cumulative effects and the memory effects of the evaporation material in the samples ablation chamber of the different volumes were studied. The experimental results showed that with the increase of the sample chambers volume, the data of the spectral intensity were increasing with the increase of the acquisition spectrum number; after the laser was closed, the washing time of the samples sediment in the sample chamber was significantly increased. After the volume of the sample chamber was reduced, the spectral intensity quickly tended to be stable with the increase of the acquisition spectrum number. The washing time of samples sediment was shortened. But the volatility of the spectral signal was largened markedly.Fourth, when the sample chamber is 60cm3, the stability and reproducibility of the spectral intensity and signal-to-background ratio were studied. In the transport process, when no buffer measures was taken, the volatilities of the spectra measured signals were large by using the high-energy laser to ablate the soil; when the buffer device of the appropriate volume was linked on the transportion tubes, the relative stable spectrum signal can be obtained under the circumstance of the higher laser output energy and the smaller the ablation chamber.