Ion SourcesSome characteristics of ion sources (especially in high precision work):

• It should have high efficiency in generating ions of the element of interest (or a range of elements).

• All of the ions should have the same energy.

• It should produce an ion beam with low divergence.

• The ions should be the same charge (preferably +1 for positive ions or -1 for negative ions) so we separate by mass and not m/q.

• The ion beam should be stable.

• The ion beam should have isotopic ratios the same as the sample.

Thermal Ionization MSThermal Ionization MS

AdvantagesAdvantages

– Extremely StableExtremely Stable– Generally less prone to Generally less prone to

isotopic fractionation isotopic fractionation effects than other effects than other sourcessources

– Thermalized ions Thermalized ions (narrow energy range)(narrow energy range)

DisadvantagesDisadvantages

– Complicated sample Complicated sample preparationpreparation

– Incomplete isotope Incomplete isotope (elemental) coverage(elemental) coverage

» Inconsistent positive or Inconsistent positive or negative ionization negative ionization efficiencies across efficiencies across periodic tableperiodic table

Inductively Coupled Plasma MSInductively Coupled Plasma MS

AdvantagesAdvantages

– High sensitivityHigh sensitivity– Nearly complete Nearly complete

isotope coverageisotope coverage– Liquid, solid or gas Liquid, solid or gas

samplessamples– Short analysis timesShort analysis times– Less “art”Less “art”

DisadvantagesDisadvantages

– Isobaric interferencesIsobaric interferences– Relatively noisyRelatively noisy– Wide ion energy spreadWide ion energy spread– InefficientInefficient– Spectral complexitySpectral complexity

So what is the ICP?So what is the ICP?

What equipment does it require?What equipment does it require? How does it operate?How does it operate? What are its features?What are its features? How does it work with MS?How does it work with MS?

Basic ICP InstrumentBasic ICP Instrument

SampleSampleIntroductionIntroduction

SystemSystemICPICP

ReadoutReadoutSystemSystem

SpectrometricSpectrometricSystemSystem

Inductively Inductively Coupled Plasma Coupled Plasma

- Atomic - Atomic Emission Emission

Spectrometry Spectrometry (ICP-AES)(ICP-AES)

Nebulizer

SprayChamber

Torch

99%99%

Types of ICP NebulizersTypes of ICP Nebulizers

Concentric pneumaticConcentric pneumatic Cross-flow pneumaticCross-flow pneumatic Ultrasonic (high sensitivity)Ultrasonic (high sensitivity) High-solids (V-groove, Babington, etc.)High-solids (V-groove, Babington, etc.) ……....

Types of ICP Spray ChambersTypes of ICP Spray Chambers

Scott-typeScott-type High-efficiencyHigh-efficiency CyclonicCyclonic DesolvatingDesolvating ……....

The Inductively Coupled PlasmaThe Inductively Coupled Plasma A plasma is a hot, partially ionized gas.A plasma is a hot, partially ionized gas. The ICP is an argon-based, radio frequency plasma.The ICP is an argon-based, radio frequency plasma. The input rf frequency is either 27 or 40 MHz at The input rf frequency is either 27 or 40 MHz at

powers from 1 to 2 kW.powers from 1 to 2 kW. The plasma is formed and contained in a three tube The plasma is formed and contained in a three tube

quartz touch.quartz touch. The temperature in the central analyte channel ranges The temperature in the central analyte channel ranges

from about 6000 to 8000° K.from about 6000 to 8000° K. At these temperatures most elements are largely At these temperatures most elements are largely

atomized and ionizedatomized and ionized

The ICP Torch and PlasmaThe ICP Torch and Plasma

THE STEPSTHE STEPS

THE STEPSTHE STEPS

ICP torch, ICP torch, nebulizer, nebulizer,

spray spray chamberchamber

Inductively Coupled Plasma (ICP)Inductively Coupled Plasma (ICP)Tail Flame

Induction (Load) Coil

Normal Analytical Zone

Sample Aerosol

Y+

Y

YO

ee-- + Ar + Ar Ar Ar++ + 2e + 2e--

Inductively Coupled Plasma (ICP)Inductively Coupled Plasma (ICP)

Mass Mass SpectrometerSpectrometer

hν

Inductively Coupled Plasma - Inductively Coupled Plasma - Mass SpectrometryMass Spectrometry

ICP-MS ICP-MS Interface Interface

ConesCones

Supersonic ExpansionSupersonic Expansion

X MS a m p l i n g P l a t e

B a r r e l S h o c k

M a c h D i s k

M o l e c u l a r F l o w

T r a n s i t i o n F l o w

C o n t i n u u m F l o w

X m a x

0.0000 'BY

MY

RY

Consequences of ExpansionConsequences of Expansion

€

KEAr =5

2kT

Small ions

Ar

Ar

Ar

Ar

Ar

Ar

ArCs

Li

Large ions

KE = 0.5 MVKE = 0.5 MV22

So KESo KEMM++ = kM = kM++

Plasma Offset (Rectification)Plasma Offset (Rectification)

Mass Mass SpectrometerSpectrometer

+

—e-

Plasma Offset (Rectification)Plasma Offset (Rectification)

Mass Mass SpectrometerSpectrometer

—

Ar+

+

Ion Energies Depend on MassIon Energies Depend on Mass27 MHz - open symbols27 MHz - open symbols40 MHz - closed symbols40 MHz - closed symbols - “hot” plasma- “hot” plasma - “cold” plasma- “cold” plasma

Ion Currents Ion Currents in ICP-MSin ICP-MS

Spectral Characteristics of ICP-MSSpectral Characteristics of ICP-MS

ICP-MS Background: 5% HClICP-MS Background: 5% HCl

ICP-MS ICP-MS Background: Background: 5% H5% H22SOSO44

Oxide and Hydroxide SpeciesOxide and Hydroxide Species

Variables Affecting Oxide LevelsVariables Affecting Oxide Levels

Matrix Induced Signal ChangesMatrix Induced Signal Changes

Matrix Matrix Effects in Effects in ICP-MSICP-MS

ICP-MS Options for Isotope RatiosICP-MS Options for Isotope Ratios Multi-collector sector-field spectrometerMulti-collector sector-field spectrometer

– Offered by Thermo (Neptune), GV, and NuOffered by Thermo (Neptune), GV, and Nu– Isotope-ratio precision ~0.002% rsd (20 ppm)Isotope-ratio precision ~0.002% rsd (20 ppm)

Time-of-flight mass spectrometerTime-of-flight mass spectrometer– Leco & GBCLeco & GBC– Isotope-ratio precision ~0.05% rsd analogIsotope-ratio precision ~0.05% rsd analog– Isotope-ratio precision ~0.01% rsd countingIsotope-ratio precision ~0.01% rsd counting

Array-detector sector fieldArray-detector sector field– Not yet commercially availableNot yet commercially available– Isotope-ratio precision ~0.007% rsdIsotope-ratio precision ~0.007% rsd

Thermo Neptune MC-ICP-MSThermo Neptune MC-ICP-MS

Nu Instruments MC-ICP-MSNu Instruments MC-ICP-MS

Leco Renaissance ICP-TOFMSLeco Renaissance ICP-TOFMS

GBC Optimass ICP-TOFMSGBC Optimass ICP-TOFMS

Ion SourcesThermal Ionization MSInductively Coupled Plasma MSSo what is the ICP?Basic ICP InstrumentInductively Coupled Plasma - Atomic Emission Spectrometry (ICP-AES)Types of ICP NebulizersTypes of ICP Spray ChambersThe Inductively Coupled PlasmaThe ICP Torch and PlasmaTHE STEPSSlide 12ICP torch, nebulizer, spray chamberInductively Coupled Plasma (ICP)Slide 15Inductively Coupled Plasma - Mass SpectrometryPowerPoint PresentationICP-MS Interface ConesSlide 19Slide 20Slide 21Supersonic ExpansionConsequences of ExpansionPlasma Offset (Rectification)Slide 25Ion Energies Depend on MassIon Currents in ICP-MSSpectral Characteristics of ICP-MSICP-MS Background: 5% HClICP-MS Background: 5% H2SO4Oxide and Hydroxide SpeciesVariables Affecting Oxide LevelsMatrix Induced Signal ChangesMatrix Effects in ICP-MSICP-MS Options for Isotope RatiosThermo Neptune MC-ICP-MSNu Instruments MC-ICP-MSLeco Renaissance ICP-TOFMSGBC Optimass ICP-TOFMS