Method And Application Of ICP-MS Multiple Techniques For Heavy Metals In Atmospheric Particles

Heavy metals,which adsorbed on the atmospheric particles in the form of the loose binding,are constantly a great concern of the scientific community and general public because of their detrimental health effects.Through the content and isotopic ratio of heavy metals in the atmospheric particles,contamination status,the source of pollutants and the transformation process in biogeochemical cycle are understood.Inductively Coupled Plasma Mass Spectrometry?ICP-MS?is used frequently in analysis of heavy metals in atmospheric particles because it has high sensitivity,wide linear range,multielement determination and isotopic ratio analysis and has been recognized as the most powerful trace and ultra-trace inorganic element analysis technique.However,there are still many questions about analysis of heavy metals in atmospheric particles,such as cumbersome procedures,time-consuming,easy to introduce pollution and so on.In this paper,two new sample introduction systems?Laser ablation sample introduction system and Cold vapor generation?,in conjunction with ICP-MS were used for analysis of the heavy metal content and isotopic ratio in atmospheric particles.And the rapid and environmentally friendly novel methods were improved and applied for analysis of the heavy metals in atmospheric particles.Laser ablation sample introduction system,which can measure solid samples directly,in conjunction with ICP-MS,can avoid complex sample pretreatment process,shorten analysis time,and reduce the sample loss and so on.In this paper,a novel method was improved for the rapid determination of 11 metals?Be,Mn,Fe,Co,Ni,Cu,Zn,Se,Sr,Cd,Pb?in particles by laser ablation-inductively coupled plasma-mass spectrometry?LA-ICP-MS?.In this method,solid standards are prepared by depositing droplets of aqueous standard solutions on the surface of a membrane filter,which is the same type as used for collecting atmospheric pollutant metals.The mode of radial line scans across the filter disc was a representative ablation strategy and can avoid error from the inhomogeneous filter standards and marginal effect of the filter disc.Laser parameters were optimized.And laser diameter of 135?m,ablation frequency of 20Hz,laser energy of 6 mJ,coolant gas of 14 L min^-1,auxiliary gas of 0.8 L min^-1,and Make-up gas flow?Ar?of 0.6 L min^-1 were applied.Pt,as the internal standard,greatly improved the correlation coefficient of the calibration curve,0.98?Se?⁰.9998?Cu?.The developed method provides low detection limits,from 0.01 ng m^-3 for Be and Co to 1.92 ng m^-3 for Fe.It was successfully applied for the determination of atmospheric pollutant metals collected in Lhasa,China.The analytical results showed good agreement with those obtained by conventional liquid analysis.In this paper,the spatial distribution characteristics of 11 metals on the atmospheric filter samples?particle size<0.49?m?were studied by the LA-ICP-MS method with a?m spatial resolution.The results showed that there were three different types of distributions in 11 metals.A preliminary study suggests the spatial distribution characteristics of 11 metals were relation with the particle size,namely,the metals absorbed on the small particles were easily to deposit on the center of the filter and the metals absorbed on the large particles were inclined to diffuse to the edge of the filter.In addition,the concentration of heavy metals in atmospheric particles also had a certain influence for its distribution.The higher the concentration,the easier it deposited on the center of the filter membrane.Cold vapor generation?CV?,which only allows Hg vapors into plasma through stannous chloride?SnCl₂?reduction,in conjunction with ICP-MS,can improve greatly the sensitivity of Hg analysis and is widely used in the analysis of Hg content and isotopic ratio.Tl is usually used as the internal standard in Hg isotopic analysis because²⁰³Tl and ²⁰⁵Tl isotopes are close to the isotopes of Hg in the atomic mass.However,Tl is toxic,even more than mercury and is restricted severely during purchase in China because of his toxicity.In this paper,Lead was applied as an internal standard for the determination of Hg isotopic ratios.Cold vapor generation?CV?coupled with sector field-inductively coupled plasma-mass spectrometry?CV-SF-ICP-MS?was used for determination of Hg.It was effective to avoid interferences of Pb from samples while improving the sensitivity of Hg isotopic analysis by an approximate factor of 45 times higher than the aerosol mode.CV-SF-ICP-MS system was constructed and operational para-meters were optimized.Research showed that the long stability of the system was limited by SF-ICP-MS and had no relationship with CV under the optimized conditions.The optimized precision of Hg isotopic ratio analysis was approximately 0.1%during4 h.Five models were applied for the mass bias correction and the Baxter model obtained the smallest relative difference,0.52‰.The results showed that the mean value of NIST SRM 3133 Hg isotopic ratios obtained by Pb internal standard was nearly identical with the value for Tl.The same performance was also obtained in two environmental reference materials.The results show that Pb may be used as the internal standard for determination of Hg isotopic ratio instead of Tl.