ICP-MS 干扰消除技术的选择及其在环境样品分析中的应用.ppt

* * RF Power Increasing Rf power dissociates oxide ions more efficiently MO+ oxide levels drop  M+ analyte signal increases Increasing the Rf power leads to increases of doubly charged ions M+ M++ Increasing power first increases, then decreases singly charged analyte ion intensity MO+ M+ M++ * Nebulizer Argon Flow Increasing the flow first increases then decreases M+ Increased nebulizer flow reduces the plasma temperature Decreases M++ Increases MO+ * ICP Parameter Interaction RF power, nebulizer argon flow and sampling position interact extensively At every preset RF power, one can achieve “optimum” analytical conditions which are unique for the selected power Best compromise for sensitivity, noise, oxide, and doubly charged ion levels is typically only achieved within a small RF power range Do not changed Plasma RF power on a daily basis, unless necessary. Typical RF power for normal sample types should be within 1000 W to 1300W Higher power levels only are required for the analysis of organic solvents (1400 W to 1500 W) * * * 98 * * * * * * * * * * Spectra to show that As+ is being converted to AsO+. All peaks in red were acquired in standard mode; all peaks in blue were acquired in DRC mode (O2=0.45 mL/min). In standard mode, notice the large peak at 75As+ and lack of peak at m/z 91. When O2 is turned on, the peak at m/z 75 disappears, while a peak at m/z 91 appears. This provides further evidence the As+ is converted to AsO+. * * * * 雾化气流量对离子强度的影响 Increasing Nebulizer Argon Flow Intensity ICP参数之间对离子强度的影响 Increasing Nebulizer Argon Flow Intensity 900W 1000 W 1100W 1200W 质谱干扰的消除（2）——选择同位素、干扰校正方程 尽量避免或者降低同质异位素干扰 比如： Ca43 Fe57 使用干扰校正方程： …… Spectral Interference - Isobaric Corrections Predictable Cl- Molecular Species Molecular Ion Abund. (%) Interfered Isotope Abund. (%) 38 Cl 18 O 0.05 55 Mn 100 37 Cl 16 O 1 H 24.4 54 Fe 37 Cl 17 O 1 H 0.01 55 Mn 35 Cl 40 Ar 75.2 75 As 100 35 Cl 38 Ar 0.05 73 Ge 7.76 35 Cl 36