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Hyphenated Technique of Capillary Hyphenated Technique of Capillary Electrophoresis and Inductively Coupled Electrophoresis and Inductively Coupled
Plasma Mass spectrometryPlasma Mass spectrometry
Jesús Anzano
University of Zaragoza– Department of Analytical Chemistry
Zaragoza
• Introduction: a. Elemental Speciationb. Capillary Electrophoresis (CE)c. Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
• CE-ICP-MS Hyphenated Systema. CE-ICP-MS Instrument Setupb. Interface and Modified Nebulizer Designc. Direct Injection Interface designd. Pulsed Field Capillary Electrophoresise. Laminar Flow Effect
• Elemental Speciation Analysis applicationa. Chemical forms of As and Cr in preservative woodb. Leaching effect of As and Cr in surround soil
• Preliminary Results
OutlineOutline
Elemental SpeciationElemental Speciation
• Elemental Speciation is the identification and quantification of the chemical form of an element.
• The toxicological, physiological and biological effects are species dependent.
• Main area:---Environmental area
---Food area
---Health area
Capillary Electrophoresis (CE)Capillary Electrophoresis (CE)
• Separate mixture of ionic species quickly
• Good resolution and separation efficiency
• Simple instrument set-up
• Relative low cost
• Require much less sample
Inductively Coupled Plasma Mass Inductively Coupled Plasma Mass spectrometry (ICP-MS)spectrometry (ICP-MS)
• Direct element information and quantification
• Species identification via migration time
• Low detection limit
• High sensitivity and selectively
CE-ICP-MS Instrument SetupCE-ICP-MS Instrument Setup
Quadrupole Mass Analyzer
Detector
Computer
ICP
Interface
UV Detector
Buffer / SampleMake-up Solution
Capillary
CE HV Power Supply
ICP Nebulizer
Flow From CE Capillary
CE Platinum Ground Electrode
Make-up Sheath Flow
O-ring
The CE-ICP-MS InterfaceThe CE-ICP-MS Interface
Requirements:An electrical connection to the end of CE capillaryHigh aerosol transport efficiencyLow dead volume
Nebulizer Gas In
CE Capillary
Stainless Steel Tube To Spray Chamber
CE CapillaryStainless Steel Tube
Nebulizer Inner Tube
The Modified Concentric NebulizerThe Modified Concentric Nebulizer
TheThe Concentric Nebulizer and InterfaceConcentric Nebulizer and Interface
• Advantages: - Universally applicable - Easy to install and remove - Inexpensive
• Disadvantages: - Sample solution from CE is diluted and causes losses in
sensitivity. - Increase sample solution flow rate may decrease CE
resolution. - Decrease make-up sheath flow rate may decrease ICP-
MS aerosol transfer efficiency
Nebulizer Gas
Platinum Electrode
CE Capillary
Nebulizer Body
ICP Torch
Sampler Cone
The Direct Injection InterfaceThe Direct Injection Interface
The Direct Injection InterfaceThe Direct Injection Interface
• Advantages: - Improve precision.
- Reduce rinse-out time.
- Low absolute detection limit.
- Reduce peak broadening due to the low dead volume.
• Disadvantages: - ICP-MS plasma may be extinguished.
- High cost.
- Difficult to use.
VV
AA
Sample or Buffer
UV Detector
Current
Voltage Probe
Pulse Power Supply
Capillary
InterfaceNebulizer
To ICP
Capillary with Silver Paint
+G
Pulsed Field CE-ICP-MS Instrument SetupPulsed Field CE-ICP-MS Instrument Setup
Continuous s or ms,Pulsed
DC
20kV, 40A
0.8W
Dc: 5kV, 10A (0.05W)
Pulse: 100kV, 0.2mA, 100s, 200Hz (20W)
Average: 0.45W
t1
t2
Pulse
DC
Pulsed Field CE-ICP-MSPulsed Field CE-ICP-MS
Comparison of power consideration for a continuous versus pulsed CE
Pulsed Field CE-ICP-MSPulsed Field CE-ICP-MS
• Theoretical plate number N=L2/L2=(ep+eo)V/2D (1)
• Resolution Rs= N1/2 (v /) /4 (2)
• Plate Height Hheating =(2S22/2D)((K1E5rc6/app)
+ (K2 E6 rc6/LD)) (3)
Where V is the applied voltage, E is the electric field strength.
1. Kennedy, R. T.; German, I.; Thompson, J. E.; Witowski, S. R. Chem. Rev. 1999, 99, 3081-3131.
The effect of Joule heating on band broadening
Pulsed Field CE-ICP-MSPulsed Field CE-ICP-MS
• Advantages: - Reduce the Joule heating which causes
band broadening in conventional CE.
- Large diameter capillary can be used to attain high flow rate.
- The interface is simpler and high sensitivity without dilution of the analyte.
• Disadvantages:- High cost.
Cross-Sectional Flow Profile Due to Electroosmotic Flow
Cross-Sectional Flow Profile Due to Laminar Flow
Laminar Flow Effect in CE-ICP-MSLaminar Flow Effect in CE-ICP-MS
Elemental Speciation Analysis ApplicationElemental Speciation Analysis Application
Major consideration:• The toxicity of copper (Cu), chromium (Cr) and
arsenic (As) is dependent on elemental species. • Preservative wood and soil sample Preparation.
•The state of As and Cr on treated wood. •The effect of pH on leaching of As and Cr. •As and Cr leach from the treated wood into soil..
The most widely used wood preservative is chromated
copper arsenate (CCA)
Preliminary ResultPreliminary Result
The concentric nebulizer and interface
Design 1
Design 2
Design 3
Design 4
CE liquid flow
Make-up buffer
Torr seal
The Configuration of Nebulizer Tip
0.E+00
1.E+05
2.E+05
3.E+05
4.E+05
5.E+05
6.E+05
7.E+05
8.E+05
9.E+05
1.E+06
0.500 0.600 0.700 0.800 0.900 1.000 1.100 1.200
Modified Nebulizer gas flow rate (L/min)
1ppm
In si
gnal
(acp
s)Modified Nebulizer Gas Flow Rate Effect
0.0E+00
5.0E+05
1.0E+06
1.5E+06
2.0E+06
2.5E+06
3.0E+06
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
Make-up sheath flow rate (mL/min)
1pp
m I
n s
ign
al (
acp
s)/s
olu
tion
flo
w r
ate
(mL
/min
)Make-up Sheath Flow Rate Effect