八级杆工作原理ICPMS实用教案

1、Page 1What is a Collision/Reaction Cell? The Octopole Reaction System (ORS) is an octopole ion guide contained within a stainless steel vessel and pressurized with a gas, most often H2 or He. The ORS is positioned between the ion lens assembly and the quadrupole mass filter. As ions from the sample

2、enter this cell, they interact with the gas, resulting in the reduction of the molecular interference normally below the level of the blank solution. Eliminates key interferences arising from the sample matrix that are not argon based and cannot be eliminated using “traditional” approaches.第1页/共12页第

3、一页，共13页。Page 2Why use an Octopole? (1)= analyte ionOctopole Reaction SystemInitial Ion Energy Energy After CollisionSmall diameterIons entering the reaction cell have an ion energy in the radial direction corresponding to the dotted line labelled Initial Ion Energy. As ions enter the cell and intera

4、ct with the reaction gas, energy transfer takes place and the analyte ions lose energy. When ions lose energy (Energy After Collision), the voltages placed on the reaction cell force the ions to move along the potential energy distribution (drawn in black) and the ions are subsequently confined with

5、in the shaded region. Note that the confinement area in the Octopole design is relatively diffuse. A small diameter Octopole can be used to physically confine the ions into a tightly focused ion beam.第2页/共12页第二页，共13页。Page 3Why use an Octopole? (2)= analyte ionQuadrupole Based Reaction CellsInitial I

6、on EnergyEnergy After CollisionCollisional FocusingIn contrast to the Octopole design, ions which lose energy in a quadrupole reaction cell are confined to a narrow potential field. This effect is known as collisional focusing and is required in systems having inherently low sensitivity or in which

7、the reaction cell and the mass analyzer are of the same physical diameter. Collisional focusing requires a large number of ion molecule interactions within the cell to ensure ion energy loss. Therefore, highly reactive, heavy molecular gases are often required with these designs to prevent dramatic

8、loss of sensitivity. Complex ion filtering techniques are often utilized with this configuration to remove reaction by-products caused by highly reactive gases used in the cell increases complexity and reduces sensitivity.第3页/共12页第三页，共13页。Page 4Processes in the Cell ORS can be operated without using

9、 highly reactive gases. Octopole design allows higher cell pressures increasing reaction cross section due to better ion beam focussing He Mode Collisionally Induced Dissociation the interference is broken apart when it impacts the He atom Energy Discrimination the larger polyatomic species (greater

10、 ionic radii) loose more energy than the smaller analyte species and cannot enter the QP effectively a molecular filter Aided by the Agilent ShieldTorch System all ions enter the Octopole with well-defined narrow energy distribution H2 Mode Charge Transfer electron transferred from (or to) hydrogen,

11、 producing a neutral species Actually both modes use Energy Discrimination, at least in part第4页/共12页第四页，共13页。Page 5Collisionally Induced Dissociation (CID) Helium ModeArNaHeHeHeHeHeHeArNaHeHeHeHeHeMolecular species enter the cellThey collide with the He atomsThe collision breaks the species apartThe

12、 collision breaks the species apartThe interference has been neutralised第5页/共12页第五页，共13页。Page 6Energy Discrimination Ionic Radii050100150200250300Simple SpeciesAs+ArCl+V+ClO+Ionic Radii (pm)Any polyatomic species will have a larger-cross section than single ionsThe larger polyatomics will collide wi

13、th the cell gas a greater number of times than the smaller analyte ions and loose energyLow energy ions cannot enter the QPm/z 75m/z 51第6页/共12页第六页，共13页。Page 7Energy Discrimination Ionic Radii050100150200250300350400Complex SpeciesCuS2SO2NOClArMgCaOHIonic Radii (pm)Energy Discrimination is NOT a reac

14、tion process does NOT rely on reaction pathways that are species dependantSimply acts as a physical filter for the larger polyatomic ionsIs applicable for ANY polyatomicm/z 65第7页/共12页第七页，共13页。Page 8Energy Discrimination (ED)Helium ModeHeHeHeHeHeHeHeHeHeAs+ArCl+HeHeSmaller analytes loose less energy

15、than polyatomicsThey collide with few He atoms and can enter the QPLarger polyatomic species collide more timesEach collision reduces ion energyQP at +3 Vc.f. OPPositive QP repels low energy polyatomic species Polyatomic cannot enter QP第8页/共12页第八页，共13页。Page 9ED & CID In Action 7500c Tune ScreenS

16、creen capture of He-mode tuning.Solution contains 1.1g l-1 NaCl.System set to monitor 40Ar23Na (interferes with 63Cu) and 40Ar35Cl (interferes with 75As) and 65Cu (background contamination)Cell is pressurized and depressurized with He (at 0.0 & 4.0ml min-1)Note residual Cu contamination in NaCl

17、saltClick Image to play movie第9页/共12页第九页，共13页。Page 10Charge TransferHydrogen ModeHHeeInterfering ion enters Octopole and collides with H2An electron is transferred to the interferenceArAr+The interference is neutralised and hydrogen gains the chargeHeeH+Neutral species cannot enter off-axis QP第10页/共12页第十页，共13页。Page 11Reaction Mode 7500c Tune ScreenClick Image to play movieScreen capture of H2-mode tuning.Solution contains 10ppb Tl and no Se.System set to monitor 40Ar