Determination Of Os And Pb By Inductively Coupled Plasma Mass Spectrometry After Photochemical Vapor Generation

The development of sensitive analytical methods for the analysis of trace/ultratrace elements in environmental samples is an important research field in analytical chemistry.Inductively coupled plasma mass spectrometry(ICP-MS)is a powerful tool for the determination of trace metals with the advantages of low detection,wide dynamic ranges,and high spectral resolution for elements and isotopes.Recently,photo-induced chemical vapor generation(PVG),utilizing free radicals produced by photo-redox reactions as reductants,is demonstrated to be a simple,interference-minimized and environmentally friendly sample introduction technique in atomic spectrometry.In this work,new PVG methods were developed and combined with inductively coupled plasma spectrometry for the determination of trace and ultratrace Os and Pb in environmental samples.This dissertation mainly includes the following two parts:1.Accurate analysis of osmium is important in geochemistry and geochronology.The current osmium analytical methods often suffer from low sensitivity,multi-step extraction,high procedural blank,and severe memory effect.In this work,a highly sensitive and simple method for the determination of osmium in natural waters was developed by coupling inductively coupled plasma-mass spectrometry with photochemical vapor generation.The procedural blank is low due to the needlessness of high concentration strong oxidant.What's more,the memory effect was successfully solved by using 5.0% ammonium hydroxide elution instead of using concentrated inorganic acid or oxidant reagent reported before.Under optimized conditions,the detection limit was 0.8 pg mL-1.A precision of 3.2%(RSD,n=5)was achieved at a concentration of 1 ng m L-1.The accuracy is successfully validated in several natural water samples with spike recoveries from 97% to 106%.The proposed method is sensitive,simple,low blank,and memory effect-free,which has a great potential in relevant geochemistry and geochronology study.2.lead is toxic to human being,aquatic plants and animals even at trace level,and it is wildly regarded as a good indicator of heavy metal pollution in marine environments caused by anthropogenic activities.Elucidation of the distribution and concentration of lead in seawater is of great importance for the identification of contamination source and contamination prevention.However,direct determination of lead in seawater samples remains a challenge due to their extremely low concentrations and their high-salt matrix.A novel method was developed for the determination of lead in seawater samples using nickel-assisted photochemical vapor generation(PVG)coupled with inductively coupled plasma mass spectrometry(ICP-MS).The severe matrix effect of seawater on the suppression of lead signal was efficiently eliminated by using a mixture of 15 ?g g-1 Ni2+ and 10%(v/v)formic acid as photochemical reduction medium,making direct determination of Pb in seawater samples feasible.A method detection limit of 0.003 ng g-1 based on external calibration was obtained,along with the sampling frequency of 20 h-1 was achieved with a 30 s sample loading time and a 1.25 mL sample consumption.The relative standard deviation of measurement results is 3.7%(RSD,n=6)in seawater spiked with 1 ng g-1 Pb2+ solution.The proposed method was successfully applied for the analysis of three seawater samples(collected from Shanghai,Haikou and Sanya,China),with the spike recoveries ranged from 95.2% to 108.9%.