CHEM 4631 Exam 3: Lecture Slides 20

What are some advantages of ICP?

• Lower susceptibility to chemical interferences (higher temperatures)

• Good emission spectra for most elements with same experimental setup (can record all at the same time)

• Can determine low concentrations of refractory compounds (i.e. oxides)

• Can determine non-metals

• Larger linear range

What are some disadvantages of ICP?

• Spectra are highly complex (increases probability of interferences for quantitative work)

• Expensive equipment (more difficult to maintain)

What is Plasma?

Electrically conducting gaseous mix that reaches extreme temperatures (10000 K) and has high concentrations of cations and electrons

What is the source of ICP called?

A Torch

What does ICP consist of?

• Three concentric quartz tubes

• Water cooled induction coil

What are the Advantages of having the Torch orientated Axially?

• Increased radiation intensity

• Longer path length

• Higher precision

• Lower detection limits

• Better fro ICPMS

What are the Disadvantages of having the Torch orientated Axially?

• Plasma tail in the light path

• Thermal and containment degradation of spectrometer optics

What are some properties of Plasma?

• Very intense

• Brilliant white

• Nontransparent core

• Flame-like tail

For Sample Introduction (Solids and Liquids), how is ICP similar to AAS?

• For liquids, ICP aspirates (Nebulization) the sample into the plasma

• Liquids and Solids can use Electrothermal Vaporization, but only for sample introduction and not atomization.

What happens during Laser Ablation?

• Laser is intense enough to vaporize sample and particles are carried by Ar Gas

• Particles are then atomized in the Plasma

• Very expensive sample intro method

What are some Advantages to Plasma in ICP?

• More complete atomization in plasma

• Fewer chemical interferences

• Less oxide formation

• Plasma temp is more uniform

• Larger linear range for Cali Curves

• Significant ionization

What are the different types of ICP?

• Sequential

• Simultaneous Multichannel

• Fourier Transform (FT)

What type of grating does the monochromator have on the Sequential ICP?

Holographic Type (2400-3600 grooves/mm)

What type of Grating does the Monochromator of an ICP have?

Eschelle/Echellete

What parts of the monochromator of a Sequential ICP can be moved/rotated?

• The grating can rotate

• The slit and detectors can be moved while having the grating at a fixed position

How many detectors and what kind are in a Sequential ICP, and what does an Hg Lamp do?

• 2 PMT Detectors

• The Hg Lamp calibrates the wavelength

What is a Slew-Scan and what is the Advantage and Disadvantage of this scan?

Instrument scans quickly to region of interest and then slows down to 0.01 – 0.001 nm steps.

Advantage: Can scan 15 elements in 5 minutes

Disadvantage: Consumes the most sample than other designs

What does a Scanning Echelle Spectrometer do in ICP?

A PMT detector moves to scan an aperture plate with 300 slits/holes, and each movement takes around 1 second