Introduction of samples into ICP

Samples

l    Liquid (wet or dry aerosol)

l    Solid (dry aerosol, direct solids vaporization)

l    Gaseous (volatile compounds and gases)

Requirements for an aerosol properties

l    Efficient generating of aerosols independent of sample properties

l    Good efficiency of an aerosol transport

l    Minimum memory effects

l    Stability of an aerosol generating and transport

l    Identical composition of a sample and aerosol

l    Dominant yield of fine particles (mm)

                                     Liquid sample introduction

1) Nebulization of solutions

  a) Pneumatic nebulization (Gouy 1879)

    l  Capillary nebulizers - with/without suction

      4Concentric nebulizer - with aspirating effect (Meinhard 1977)

      4Cross-flow nebulizer - with/without suction (Kniseley 1974, Boumans 1982)

    l  Babington-type nebulizers - no suction effect (Babington 1973)

      4V-groove nebulizer  (Wolcott & Sobel 1978)

      4Grid nebulizer  (Hildebrand)

      4Fritted disc nebulizer  (Apel & Bienewski 1977)

      

                                     Liquid sample introduction

1) Nebulization of solutions (continued)

   b) Nebulization independent of a carrier gas flow

    4Jet-impact nebulizer  (Doherty & Hieftje 1984)

    4Hydraulic high pressure nebulizer  (Knauer)

    4Thermospray

    4Ultrasonic nebulizer  (Dunken & Pforr 1963)

2) Electrothermal vaporization (ETV)

   a) Electrically heated metal vaporizers

    4Ta filament vaporizer  - resistance heating  (Nixon, Fassel & Kniseley 1974)

    4Tungsten loop - cathode of m-arc (Keilsohn, Deutsch & Hieftje 1983)

                                     Liquid sample introduction

2) Electrothermal vaporization (continued)

  b) Electrically heated graphite vaporizers

    4Graphite rod  (Gunn, Millard Kirkbright 1978)

    4Graphite cup  (Ng & Caruso 1982)

    4Graphite furnace  (Aziz, Broekaert & Leis 1982)

3) Direct sample insertion devices

  Samples inserted axially (in injector position) into ICP -induction and contact heating

    4Graphite electrode (Salin & Horlick 1979)

    4Graphite crucible (Sommer & Ohls 1980)

                                     Liquid sample introduction

4) Hyphenated techniques

4   Liquid chromatographic techniques  (Van Loon 1979)

4   Flow injection techniques  (Greenfield 1981)

                                    Gaseous sample introduction

4   Generation of volatile hydride (As, Sb, Bi, Se, Te, Ge, Sn) (Thompson, Pahlavanpour, Walton &
Kirkbright 1978)

4   Volatile b-diketonates of Co, Cr, Fe, Mn, Zn  (Black & Browner 1981), dithiocarbamates,
fluoroacetonates

4   Gas chromatographic separation  of organic compounds with ICP detection: F, Cl, Br, I, B, C, S,
P, O, N. (Windsor  & Bonner Denton 1979)

4   Air introduction - purity check (Trassy)

                                     Solid sample introduction

1) Powdered samples

  4  Nebulization of slurries  (Mohamed, Brown & Fry 1981)

  4  Electrothermal vaporization

  4  Fluidized bed  (Nimalasiri, de Silva & Guevermont 1986)

  4  Direct solid insertion device

  4  Laser ablation  (Abercrombie, Silvester & Stoute 1977)

2) Compact samples

  4  Electric arc erosion (ablation)  (Dahlquist 1975)

  4  Electric spark erosion (ablation) (Human, Oakes, Scott & West 1976)

  4  Laser ablation

                                       Pneumatic nebulization

l   Three main types of liquid breakup:

4  dropwise, stringwise, filmwise - depending on the relative velocity of the gas compared with the
liquid.

4  As the relative velocity changes, so does the breakup pattern, quite independently of the liquid
nebulized.

4  The transition points for different liquids are within the relative velocity range 5 to 50 m/s.
Increases in the relative velocity change the breakup pattern in the order dropwise to stringwise to
filmwise.

4  Most liquids breakup in a filmwise manner at a relative velocity above 50 m/s. For common ICP
nebulizers, filmwise breakup is observed.

                                       Pneumatic nebulization

l    Dropwise breakup - this pattern appears at low rel. velocities (gas to liquid) as the result of
waves set up in the rodlike liquid jet influenced by the gas flow. The rod develops a number of
nodes, and as the nodes grow, the liquid jet breaks up into drops. The thin drawn-out portions
between the drops form one to three small droplets.

l    Stringwise breakup - at higher velocity the liquid stream begins to flutter, as it is exposed
to a strong "wind" and the nodes are shattered, tailing out into long strings. The nodes form larger
droplets while the tails form smaller ones. 

                                       Pneumatic nebulization

l    Filmwise breakup - as the relative velocity is increase even further, the gas causes the drops
to become flattened and subsequently blown out into the form of a bag or a casting net with a
roughly circular rim. The bursting of this bag produces a large number of fine strings and filaments
which, in turn, form droplets. The rim, containing the major part of the original volume of the
drop, also breaks up, forming larger droplets. If the relative velocity is increased even further,
no new pattern develops, but the drops, bags, strings and filament become smaller.  



                                     Cross-flow nebulizer (CFN)
                                   with or without Venturi effect

                                     Babington nebulizer (1973)

          V-groove nebulizer = high solids nebulizer = maximum dissolved solids nebulizer

                                        Glass-frit nebulizer

                                    Grid nebulizer (Hildebrand)



                                       Pneumatic nebulization

                                   Ultrasonic nebulization (USN)

Ultrasonic nebulizer (USN) with desolvation unit



                                    Hydride generation  (HG-ICP)

                                    Hydride generation  (HG-ICP)

                                    Hydride generation  (HG-ICP)