1. Adventures in Sample Introduction for ICP-OES and ICP-MS
Geoffrey N. Coleman
Meinhard Glass Products
A Division of Analytical Reference Materials International

2. Sample Introduction Components
ICP Torches
Spray Chambers
Nebulizers
Conventional
High Efficiency
Direct injection
Accessories

3. Overview Brief review Components Torches Spray chambers Nebulizers
What’s new....

4. References Richard F. Browner, Georgia Institute of Technology
Anders G.T. Gustavsson, Swedish Institute of Technology
Jean-Michel Mermet, Universite Claude Bernard-Lyon, France
Akbar Montaser, George Washington University
John W. Olesik, Ohio State University
Barry L. Sharp, Macauley Land Use Institute, Scotland
“Pneumatic Nebulizers and Spray Chambers for Inductively Coupled Plasma Spectroscopy”, Journal of Analytical Atomic Spectrometry, 1988, 3, 613 – 652 (Part 1); 939 – 963 (Part 2).

5. Processes Nebulization Desolvation Dissociation Excitation
Starting with a “homogeneous” solution sample....
Nebulization
Desolvation
Dissociation
Excitation
All require energy and time.
There is a “domino” effect.

6. Interferences Nebulization Desolvation Dissociation Excitation
Probably 85% of significant interferences occur at nebulization, due to changes in surface tension, density, and viscosity.
These are multiplicative interferences.

7. NUKIYAMA AND TANASAWA EQUATION
Mean Droplet Size
NUKIYAMA AND TANASAWA EQUATION d
3,2
0.5
0.45 3 l g
1.5
585 V
597 10 Q + = é ë ê ù û ú s r h sr ( )
d3,2 = Sauter mean diameter - (m)
V = Velocity difference of gas-liquid - (m/s)
 = Surface tension - (dyn/cm)
 = Liquid density - (g/cm3)
 = Liquid viscosity - (Poise or dyn·s/cm2)
Ql = Volume flowrate, liquid - (cm3/s)
Qg = Volume flowrate, gas - (cm3/s)
S. Nukiyama and Y. Tanasawa, Trans. Soc. Mech. Eng., Tokyo, , Vol. 4 – 6, Reports 1 – 6.

8. Rule-of-Thumb
When the Total Dissolved Solids exceeds about 1000 ppm, changes in surface tension, density, and viscosity begin to affect the droplet size distribution and, thus, the slope of the analytical calibration curve.

9. Interferences Matrix Removal – usually not practical
Control by:
Matrix Removal – usually not practical
Swamping – risk of contamination
Matrix Matching – probably most useful
Internal Standard – line selection
Method of Standard Additions – most tedious and time-consuming

10. Single Droplet Studies
Desolvation begins
Evaporation from surface
Droplet diameter diminishes
Crust forms as solvent evaporates
Internal pressure builds
Droplet explodes
Escaping water vapor cools immediate surroundings
Particles dehydrate
Particles evaporate

11. Implications Large Surface Area/Volume Small Droplets
Faster desolvation and vaporization
Narrow Size Distribution
Consistent desolvation and vaporization
Well-defined excitation/observation zones
Virtually no signal comes from droplets larger than m
Most signal comes from < 3 m.

12. ICP Plasma Torches Tg 6000 – 9000 K Skin Effect Injection Velocity
Electric
Magnetic
Pressure/Temperature
Injection Velocity
3 – 5 m/sec to overcome skin effects
Injector diameter 1.0 – 2.4 mm i.d.
Carrier at 0.7 – 1.0 L/min
Residence Time
Highly Volatile Solvents
Chemical Interferences
Viewing Zone

13. ICP Plasma Torches End-on Viewing Must remove “tail flame”
Ground state atoms
Molecular species
Larger injector diameters – longer residence time
Significant chemical interferences
Significant sensitivity improvement – up to 10x

14. ICP Plasma Torches Outside: 16 – 18 mm Inner – Outer Gap: 0.5 – 1.0 mm
Injector: 1.0 – 4.0 mm
1.0 mm for volatile solvents
2.0 mm general purpose radial torch
2.4 mm general purpose axial torch
Demountable Injectors
Ceramic (alumina) or sapphire for HF
Flexibility
Complexity
Cost

15. ICP Spray Chambers Aerosol Conditioning
Remove droplets larger than 20 um
Gravitational settling
Inertial impaction
Evaporation
Recombination
Reduce aerosol concentration
Modify aerosol phase equilibria
Modify aerosol charge equilibria
Reduce turbulence of nebulization

16. Particle Motion in a Spray Chamber
ICP Spray Chambers
Particle Motion in a Spray Chamber

17. ICP Spray Chambers Scott Double-Pass Large volume (> 100 mL)
Large surface area
Phase equilibria
Stagnant areas
Long stabilization time
Long washout
Drainage

18. ICP Spray Chambers Cyclonic with Baffle Moderate volume: 50 mL
Moderate surface area
Entire volume swept by carrier flow
Fast equilibration
Fast washout
Sensitivity enhanced by 1.2 – 1.5x
Now most common type

19. ICP Spray Chambers Desolvation begins in the spray chamber
Extent affects droplet size
Affects amount transported to the plasma
Maintain constant temperature
Liquid on the walls must equilibrate with vapor
Minimize surface area
Drain away excess quickly

20. ICP Spray Chambers Speciation begins in the spray chamber
Volatile species in gas phase are more efficiently transported than droplets
Nebulization does not control the rate of sample introduction
Cool spray chamber (especially for organic solvents)
Minimize surface area

21. Nebulizers Pneumatic Other Specialty Self-aspirating Non-aspirating
Concentric
Cross-flow
Non-aspirating
Babington
V-groove
GEM Cone
MiraMist
Grid
Fritted
Other
Ultrasonic nebulizer
Thermospray
Spark ablation
Laser ablation
Specialty
HEN, MCN, MicroMist
DIHEN, DIN

22. NUKIYAMA AND TANASAWA EQUATION
Mean Droplet Size
NUKIYAMA AND TANASAWA EQUATION d
3,2
0.5
0.45 3 l g
1.5
585 V
597 10 Q + = é ë ê ù û ú s r h sr ( )
d3,2 = Sauter mean diameter - (m)
V = Velocity difference of gas-liquid - (m/s)
 = Surface tension - (dyn/cm)
 = Liquid density - (g/cm3)
 = Liquid viscosity - (Poise or dyn·s/cm2)
Ql = Volume flowrate, liquid - (cm3/s)
Qg = Volume flowrate, gas - (cm3/s)
S. Nukiyama and Y. Tanasawa, Trans. Soc. Mech. Eng., Tokyo, , Vol. 4 – 6, Reports 1 – 6.

23. Self-Aspirating Nebulizers
Concentric
Gouy design (1897)
Efficiency approaching 3%
Glass
Quartz
Teflon
Cross-flow
Efficiency approaching 2.5%
Sapphire

24. Self-Aspirating Nebulizers
Glass Concentric

25. Self-Aspirating Nebulizers
Glass Concentric

26. Self-Aspirating Nebulizers

27. Self-Aspirating Nebulizers

28. Self-Aspirating Nebulizers
Cross-flow

29. Non-aspirating Nebulizers
Original Babington Design (1973)
Very inefficient
Could nebulize “anything”
V-groove (Suddendorf, 1978)
Much improved efficiency, > 1%
Best choice for analysis of slurries
Best choice for analysis of used oils
Grid (Hildebrand, 1986)
Efficiency approaching 4.5%
Very difficult to maintain

30. Non-aspirating Nebulizers
V-groove
(Babington)

31. Non-aspirating Nebulizers
GEM Cone (PerkinElmer)
Efficiency ~ 1.2%
MiraMist/Parallel-Path (Burgener)
Efficiency approaching 3 %

32. Non-aspirating Nebulizers
MiraMist
Parallel-Path

33. Non-aspirating Nebulizers
Ultrasonic Nebulizer
Efficiency approaches 30%
Sensitivity improves ~10x
Droplet size < 5 m
Potentially heavy solvent load
Desolvation essential
Membrane separator available
Desolvation interferences occur (eg., As III vs. As IV)
Does not handle high solids well

34. Sample Introduction Accessories
Desolvation: Apex Q from Elemental Scientific
Sensitivity improves ~10x
Uses concentric nebulizer and cyclonic spray chamber
Desolvation interferences
High solids problematic
Available in HF-resistant version

35. Sample Introduction Accessories
Spray Chamber Cooling: PC3 from Elemental Scientific
Sensitivity improves
Reduces solvent loading
Reduces oxide interferences in ICPMS
Uses concentric nebulizer and cyclonic spray chamber
Available in HF-resistant version

36. Sample Introduction Accessories
Fit Kits couple liquid and gas supplies to the nebulizer
Especially useful for high pressure nebulizers

37. The MEINHARD® Nebulizer
Type A
Lapped ends – capillary and nozzle flush
Simple, monolithic design
Type C
Recessed capillary for higher TDS tolerance
Vitreous, fire-polished ends
Stronger suction
Type K
Recessed capillary
Lapped ends
Lower Ar flow: 0.7 L/min

38. The MEINHARD® Nebulizer
Intensity, 40 ppb
Precision, 40 ppb
BEC DL

39. The MEINHARD® Nebulizer
Type A
Lapped ends – capillary and nozzle flush
Simple, monolithic design
Type C
Recessed capillary for higher TDS tolerance
Vitreous, fire-polished ends
Stronger suction
Type K
Recessed capillary
Lapped ends
Lower Ar flow: 0.7 L/min

40. Glass Concentric Nebulizer
Advantages
Simple, single piece desgin
All glass design, inert
Permanently aligned - self aligning
Easy to use
Disadvantages
Low efficiency ( ~3%)
Glass attacked by HF
High or undissolved solids may clog capillary

41. HF-Resistant Nebulizers
Concentric nebulizers in Teflon PFA and Polypropylene from Elemental Scientific
Typical flows: 50 – 700 L/min; 1 L/min
Integral or demountable solution tubing
Efficiency: 2 – 3%
MicroFLOW PFA
PolyPro

42. HF-Resistant Kits Complete Kits include: Demountable Torch
Pt or Sapphire Injector
Adapter
Teflon PFA Spray Chamber
Teflon PFA or Polypropylene Nebulizer

43. Nebulizers

44. Nebulizers

45. NUKIYAMA AND TANASAWA EQUATION
Mean Droplet Size
NUKIYAMA AND TANASAWA EQUATION d
3,2
0.5
0.45 3 l g
1.5
585 V
597 10 Q + = é ë ê ù û ú s r h sr ( )
d3,2 = Sauter mean diameter - (m)
V = Velocity difference of gas-liquid - (m/s)
Ql = Volume flowrate, liquid - (cm3/s)
Qg = Volume flowrate, gas - (cm3/s)
Adjust annulus to increase V, but maintain Qg
Adjust capillary to decrease Ql

46. High Efficiency Nebulizer
Type A HEN

47. High Efficiency Nebulizer

48. High Efficiency Nebulizer
PN: TR-30-A3 MicroConcentric Nebulizer (Cetac) MicroMist (Glass Expansion)

49. High Efficiency Nebulizer
The HEN normally aspirates 30 – 300 L/min
Design gas flow is 1 L/min of argon
Normal operating pressure is 170 psi, 150 and 90 psi versions are available.

50. High Efficiency Nebulizer
Under normal operating conditions, a HEN exhibits a D3,2 of 1.2 – 1.5 m
“Starved” TR-30-A3 exhibits D3,2 of 3.2 – 4.2 m
Normal operating conditions for a TR-30-A3 yield a mean droplet size of about 15 m

51. High Efficiency Nebulizer

52. High Efficiency Nebulizer
Type A Nozzle Geometry
Smaller Sample Uptake Capillary
Liquid flow rate from ml/min
Small Bore Sample Input
Low Dead Volume Connection (LC, CZE)
Smaller Gas Annular Area
Higher Ar pressure - ³150 psig

53. High Efficiency Nebulizer
Applications:
Chromatography detection
Capillary electrophoresis
Liquid chromatography
Limited sample volume
Minimize speciation interferences
Very high analyte transport
Much less discrimination between volatile species and dissolved species

54. Direct Injection HEN
DIHEN is designed to be inserted directly into a demountable torch
DIHEN is dimensionally similar to HEN (see table, slide 47)
DIHEN is operationally similar to HEN, except
Normal carrier flow is 0.2 – 0.4 L/min
Minimize speciation interferences
Easily introduce highly volatile solvents
Essentially 100% transport
Large-Bore version less prone to clogging, but noisy

55. DIHEN Typical demountable torch with DIHEN in place
Detection limits better than conventional pneumatic nebulizer
Detection limits not as good as HEN