inductively coupled plasma ICP

Question 1

what is a plasma

Answer 1

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

Question 2

what do the free electric charges make the plasma

Answer 2

electrically

conductive so that it responds strongly to electromagnetic fields.

Question 3

For ICP what is used to produce plasma

Answer 3

argon

Question 4

plasma is what?

Answer 4

an electrical discharge

Question 5

how is plasma generated

Answer 5

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

Energy is transferred collisionally to Argon molecules

Question 6

Plasma at atmospheric pressure

Answer 6

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

Question 7

plasma temp. range

Answer 7

between 6 000 K and 10 000 K

Question 8

why use argon plasma

Answer 8

inert
not expensive
obtained at high purity

Question 9

important reasons why argon is plasma

Answer 9

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…)

Question 10

why are analyte elements singly charged

Answer 10

because the plasma environment is defined by Ar

Question 11

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

Answer 11

it creates a time varying magnetic field around it,

Question 12

what does a time varying magnetic field induce

Answer 12

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.

Question 13

3 detection methods

Answer 13

ICP - MS : Inductively Coupled Plasma Mass Spectroscopy

ICP - OES : Inductively Coupled Plasma Optical Emission Spectrometry

= ICP - AES : Inductively Coupled Plasma Atomic Emission Spectrometry

Question 14

what is ICP-OES and ICP-MS used for

Answer 14

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

Question 15

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

Answer 15

most of the periodic table

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

Question 16

ICP-AES uses a plasma for what

Answer 16

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

Question 17

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

Answer 17

the concentration of the element within the sample.

Question 18

ICP-MS is a technique based on…

Answer 18

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

Question 19

what is ICP-MS used for

Answer 19

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

Question 20

features of ICP-MS

Answer 20

 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

Question 21

ICP-MS vs. ICP-OES

Answer 21

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.