Term Test 2 Flashcards
Separate ions from neutral atoms, sort ion bound on m/z ratio and count how many ions hit the detector
ICP-MS
Advantages of ICP-MS
-Low detection limits (ppt)
-Large linear working range
-High productivity (multi-element, fast)
Isotope composition, not just concentration
-Can detect basically the entire Periodic table
Breaks liquid into small droplets/fine mist
Nebulizer
Remove large droplets so only fine droplets enter torch
Spray Chamber
Ar plasma created by interaction between Ar and energy from RF coil
Torch
Ion beam moving from a region of atm P (and high T) to very low vacuum
The Interface Region
Allow for transmission of ion beam while simultaneously reducing pressure
Cones
Clean up ion beam, separates ions from neutral species and photons
Ion Deflection Device
Four rods are tuned so ions are deflected at a 90 degree angle and photons and neutrals pass straight through
Quadrupole Ion Deflector
Caused when ions from the plasma or the sample (or combination of these) carry a m/z that is identical to that of the analyte ion
Spectral interferences
Four classes of spectral interference in ICP-MS
Polyatomic/molecular, Oxides/hydroxides/hydrides, Doubly charged, Isobaric (isotopes with the same m/z)
Most common type of spectral interference encountered
Polyatomic/Molecular Spectral Interference
Produced by elements in the sample combining with H, O, or OH to form molecular hydride (H), oxide (O), and hydroxide (OH) ions. These interferences occur at 1, 16 and 17 mass units higher than the original element mass. Typically produced in the cooler zones of the plasma, immediately before the interface region
Oxides/Hydroxides/Hydrides
Species formed when an ion is generated with a double positive charge. Produce a peak at half its mass
Double Charge Interferences
Produced when different isotopes of other elements have the same m/z as the analyte
Isobaric Interferences
This reduces spectral interferents but also reduces analyte signal
Collision Cell
True or False? large species = more collisions = more KE at end of cell
False
*less KE at end of cell
Reduces background while preserving analyte signal
Reaction Cell
Convert beam of ions into an electrical signal that can be processed
Transducer
The study of the radiation emitted when these excited electrons return to the ground state
Atomic Emission
Function of Excitation source
- Convert sample into a cloud of atoms (atomization)
- Excite electrons in the atoms to higher electronic energy levels
Sources of Excitation
- Flame (flame photometry)
- Plasma (inductively coupled plasma or ICP)
- Electric arc/electric spark
Emission separated into its constituent wavelengths
Wavelength Selector
Electrically conducting gaseous mixture containing a significant concentration of cations and electrons, like gas but ions + electrons
Plasma
