SPRAY CHAMBER TEMPERATURE: A CRITICAL (YET OFTEN MISSING) PARAMETER IN ICP EXPERIMENTS

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SPRAY CHAMBER TEMPERATURE A CRITICAL (YET OFTEN
MISSING) PARAMETER IN ICP EXPERIMENTS

• Jerry Dulude, Ron Stux, and Vesna Dolic, Glass
  Expansion, jdulude_at_geicp.com

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Focus of this study on ICP-OES

• Effect of Spray Chamber Temperature on
• Analyte sensitivity
• Detection limits
• Matrix interferences
• Plasma robustness

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Experimental

• PE 2100 Optima DV
• Power 1450 watts
• Coolant gas 15LPM
• Aux. gas 0.2LPM
• Neb. Gas 0.7LPM
• SeaSpray concentric glass nebulizer
• IsoMist Programmable Temperature spray chamber
  with Twister Baffled Cyclonic

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IsoMist on Optima 2100DV
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IsoMist Characteristics

• Programmable from -10 to 60C in 1 degree
  increments
• Maintains temperature to within 0.1 degree
• Built-in Peltier device
• Temperature measured near the chamber surface
• No external plumbing

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Effect of Temperature on Normalized LOD (20ul/min
Uptake)
PE Optima 2100DV
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Effect of Temperature on Normalized Intensity (20
uL/min)
PE Optima 2100DV
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Transport Efficiency vs. Uptake Rate
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Unexplained Intensity Enhancement
The Phenomenon

• 200 enhancement at 60C
• 67 possible from transport efficiency
• Where is the missing 133?
• Higher energy plasma
• Smaller mean droplet size

Theories
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Theory of Sensitivity Enhancement
When water is the solvent, an increase in the
solvent loading under robust conditions leads to
an increase in the MgII/MgI ratio. the
generation of hydrogen will increase locally the
thermal conductivity of the discharge.
Todoli and Mermet, JAAS, Aug., 1998, Vol. 13,
p.730
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Humidification Test

• Measure intensity in bypass mode.
• Switch to humidification ON mode
• Re-measure intensity without changing conditions

Capricorn Argon Humidifier
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Effect of Humidification on Intensity(100ul/min
uptake rate)
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Theory of Intensity EnhancementSmaller Mean
Droplet Size

• Initiate evaporation in the chamber
• Smaller particles reach the plasma
• More efficient atomization
• Higher intensity
• Use phase Doppler particle analyzer to measure
  mean droplet size

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Sensitivity vs. Temperature(1ml/min uptake)
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Intensity and Transport Efficiency vs Temperature
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Temperature vs. Robustness(Mg/Mg Ratio) 1ml/min
uptake
1000ppm Na K 500ppm Ca
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Temperature vs. Suppression(1ml/min uptake)
1000ppm Na K 500ppm Ca
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Suppression and Intensity vs. Temperature(average
of 18 lines) 1ml/min uptake
1000ppm Na K 500ppm Ca
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Summary

• Spray chamber temperature is a critical parameter
  in ICP-OES experiments.
• Intensity is proportional to temperature.
• Suppression is unrelated to temperature.
• Plasma robustness increases with temperature.
• Constant temperature is important for all
  analyses.