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