有效提升ICP-MS灵敏度

1、有效提升ICP-MS灵敏度提纲进样系统进样系统RF线圈与炬管气体流量锥形态与真空度离轴与透镜质量分析器检测器进样系统Meinhard nebulizers (1ml/min)a cooled double-pass spray chamber传输效率很低(120%) 97 counts/fg 238UMicroMist microconcentric nebulizer (0.10.2 ul/min)a small cyclonic spray chamber 2340 counts/fg 238UFrom Becker (2007) Inorganic Mass Spectrometry P

2、rinciples and Applications. John Wiley & Sons Ltd, West Sussex, UK. Page 142进样系统Finnigan Thermo Stable Introduction System (SIS)a low-flow PFA nebulizer (50 ul/min) + quartz glass spray chamber arrangement (cyclone + Scott double-pass) Cetac Aridus II Desolvating Nebulizer Systema low-flow PFA n

3、ebulizer (120 ul/min) + 110 PFA spray chamber + PTFE membrane desolvator unit进样系统From Weyer and Schwieters (2003) Int J MS, 226: 355-3681 ppm FeStandard-coneX-coneArO ArOHThermo SIS4-6 V20-30 V550%Cetac Aridus20-30 V50-100 V1%UltraSonic Nebulizer灵敏度提高10倍多原子产率降低10倍2ml/min 适合常规分析提纲进样系统RF线圈与炬管线圈与炬管气体流量

4、锥形态与真空度离轴与透镜质量分析器检测器Radio Frequency Generator Electronic circuitsFixed-frequency crystal-controlled oscillator 27.12MHzAgilent Thermo Bruker(Varian)Variable frequency free-running oscillator 40.68MHzPerkinElmerRF功率越大，等离子炬焰温度越高，有利于离解多原子团，因此灵敏度增高、氧化物产率降低，但双电荷产率会有所增高。屏蔽圈ICP离子能量色散(Energy spread)为5-10eV，

5、通过屏蔽圈电容去耦(Capacitive decoupling)，使得能量分布5eV，显著提高灵敏度、抑制二次放电。From Nelms (2005) Inductively Coupled Plasma Mass Spectrometry Handbook. Blackwell Publishing Ltd., Oxford, UK. Page 44Agilent Shielded TorchThermo Plasma ScreenThermo Element II Guard Electrode特殊线圈PerkinElmer Elan系列+NexIon 300PlamaLok可以抑制二次放

6、电，但没有实质提高灵敏度Varian810/820+Bruker Aurora-M90Interlaced Coils 交错线圈，也没有实质提高灵敏度PlasmaLok炬管X-Y轴居中Agilent Thermo Brucker(Varian)马达定位、自动调节X-Y轴PerkinElmer Elan系列 手拧螺母2010年新款NexIon 300 马达定位 From Beauchemin (2010) Anal Chem, 82: 4786-4810提纲进样系统RF线圈与炬管气体流量气体流量锥形态与真空度离轴与透镜质量分析器检测器气体流量等离子气或冷却气 Plasma/Coolant Gas

7、 1415 L/min辅助气或中路气Auxiliary/Intermediate Gas 0.91.1 L/min 对灵敏度略有影响雾化气或样品气Nebulizer/Carrier Gas0.80.9 L/min 对灵敏度、氧化物产率影响很大LA中的增敏气体5-10ml/minH2Guillong & Heinrich (2007) JAAS, 22:1488-1494N2Hu et al. (2008) JAAS, 3:1093-1101 提纲进样系统RF线圈与炬管气体流量锥形态与真空度锥形态与真空度离轴与透镜质量分析器检测器锥界面样品锥后是扩散区(Expansion chamber

8、)，气压降到300 Pa；在穿越样品锥孔1cm的距离内，等离子热能转化为动能，气体扩散速率(2500m/s)超过声速。电子温度基本不变(5000-7500 K)，但电子密度在极短时间内( Jet中高质量段元素standard 100万cpsThermo SF-ICP-MSElement II常规(普通进样系统、锥、泵)1ppb In 100万cps Large pump + Jet-sample + X skimmer cone1ppbAridus IIAPEX7Li0.75亿1.5亿89Y1.5亿3.0亿103Rh1.35亿2.6亿115In1.9亿2.7亿175Lu1.6亿2.65亿208Pb1.0亿1.0亿238U1.4亿1.35亿Hamester, Lindemann and Rottmann (Thermo Fisher Scientific Bremen) Enhanci