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Flashcards in inductively coupled plasma ICP Deck (21)
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1
Q

what is a plasma

A

A Plasma is a gas that contains ions and free electrons.

2
Q

what do the free electric charges make the plasma

A

electrically

conductive so that it responds strongly to electromagnetic fields.

3
Q

For ICP what is used to produce plasma

A

argon

4
Q

plasma is what?

A

an electrical discharge

5
Q

how is plasma generated

A

through inductive coupling of free electrons with rapidly oscillating external magnetic field (27 MHz)

Energy is transferred collisionally to Argon molecules

6
Q

Plasma at atmospheric pressure

A

allows very high temperatures ~ 10000 C (a low pressure plasma is a fluorescent lamp)

7
Q

plasma temp. range

A

between 6 000 K and 10 000 K

8
Q

why use argon plasma

A

inert
not expensive
obtained at high purity

9
Q

important reasons why argon is plasma

A

first ionization potential of 15.75 eV

  • Higher than the first ionization potential of most other elements (except He, F and Ne)
  • Lower than the second ionization potential of most other elements (except Ca, Sr, Ba…)
10
Q

why are analyte elements singly charged

A

because the plasma environment is defined by Ar

11
Q

what happens when a time varying electric current is passed through the coil

A

it creates a time varying magnetic field around it,

12
Q

what does a time varying magnetic field induce

A

electric currents in the rarefied gas, leading to break down and formation of a plasma.
- ICP discharges are of relatively high electron density, on the order of 1015 cm-3.

13
Q

3 detection methods

A

ICP - MS : Inductively Coupled Plasma Mass Spectroscopy

ICP - OES : Inductively Coupled Plasma Optical Emission Spectrometry

= ICP - AES : Inductively Coupled Plasma Atomic Emission Spectrometry

14
Q

what is ICP-OES and ICP-MS used for

A

bulk elemental chemical analysis of just about any
material or substance (waters, biological materials, inorganic materials of all sorts, environmental, forensic, geological samples…

15
Q

what can be measured using ICP-OES and ICP-MS

A

most of the periodic table

conc. from major to parts per billion or in cases parts per trillion in solution can be measured

16
Q

ICP-AES uses a plasma for what

A

to produce excited atoms that emit electromagnetic radiation at a wavelength characteristic of a particular element.

17
Q

what does the intensity of the emission of electromagnetic radiation indicate from ICP-AES

A

the concentration of the element within the sample.

18
Q

ICP-MS is a technique based on…

A

coupling together an ICP as a method of producing ions with a mass spectrometer as a method of separating and detecting the ions.

19
Q

what is ICP-MS used for

A

quantitative multi-elemental
analysis and stable isotopic ratioing that is becoming increasingly important in biotechnology, nanotechnology, biochemistry and analytical chemistry.

20
Q

features of ICP-MS

A

 Excellent detection limit low ppb-ppt for all elements

 Wide elemental coverage from Li to U, over 70 elements measurable

 All elements determined simultaneously

 Wide dynamic range linear over 9 orders

 Routine technique
can leave system running overnight

 Small size instrument saves space in the lab

21
Q

ICP-MS vs. ICP-OES

A

MS much simpler than the optical emission spectra. Most heavy elements exhibit hundreds of emission lines, but they have only 1-10 natural isotopes in the mass spectrum.

 ICP-OES suffers from many overlapping spectral interferences from other elements and a very high background emission from the plasma itself, limiting detection limits.

 Detection limits of ICP-MS are three orders of magnitude better than ICP-OES.