1

In-house Training on ICP-MS

ICP-MS???• Inductively Coupled Plasma Mass Spectrometry or ICP-MS is

an analytical technique used for elemental determinations. • An ICP-MS combines a high-temperature ICP (Inductively

Coupled Plasma) source with a mass spectrometer. • The ICP source converts the atoms of the elements in the

sample to ions. • These ions are then separated and detected by the mass

spectrometer.

Atomic Spectroscopy Techniques

• Three techniques share the same basic

components• Atomic Absorption (Flame and Furnace)

• ICP-AES

• ICP-MS

• All three are used for the analysis of metals

Comparison of TechniquesICP-MS ICP-AES GFAAS FAAS

Detection Limits Excellent Good Excellent Good

Productivity Excellent Excellent Low Good

Precision 1-3% 0.3 – 2 % 1 – 5 % 0.1 – 1 %

Chemical Interferences

Moderate Few Many Many

Ionization Minimal Minimal Minimal Some

Mass Effects High on low mass

None None None

Dissolved solids 0.1 – 0.4 % 2 – 25 % Up to 20 % 0.5 – 3 %

# Elements 75 73 50 68

Sample Usage Low Medium Very Low High

Isotope Analysis Yes No No No

Method Development Skill required Skill required Skill required Easy

Running Costs High High Medium Low

Capital Costs Very high High Medium Low

ICP-MS Components

•Sample Introduction•Plasma Generation•Interface•Ion Optics•Mass Analyzer•Vacuum System

•Sample IntroductionDelivers finely divided sample (usually aerosol) to plasma

•Plasma SourceIon SourceAr plasma10 000K

•InterfaceAllows transfer of atmospheric pressure ion source to high-vacuum mass analyser

•Ion OpticsFocuses ion beam and helps eliminate neutral species and photons

•Mass AnalyzerSeparates and measures individual ions by mass

•Vacuum SystemProvides low pressure environment for mass spectrometer to operate effectively (no collisional losses)Enables transition from plasma to high-vacuum via interface region

The Detector

•Converts ions into electrical pulses•Magnitude of the electrical pulse is

proportional to the number of ions in sample

•Sample nebulized in spraychamber

•Argon transports sample and sustains plasma

•RF generator supplies energy to induction coil•Sample atomized and ionized in the plasma• Ions are transmitted through the interface, most of the gas removed•Quadrupole filters the ions by mass• Detector counts the ions

Steps Involved in ICP-MS

How is a Plasma formed?

Sample Introduction System

Low uptake concentric nebulizer standard•External spraychamberDouble pass glass spray chamberRoom temperature to -15º CMoves with torch

•Three channel peristaltic pump Computer controlled Smart Rinse enabled for optimized rinseout

The Plasma

• A plasma is a cloud of ionized gas• Plasma temperature 6000 - 7000 K• Most elements >90% ionized• Singly charged positive ions predominate• Small molecular and doubly charged ion population• Complete elemental analysis in a single determination

ICP-MS Torch

Process to form Plasma

•A flow of argon gas is passed between outer and middle tube of torch

• RF power is applied to load coil producing intense electromagnetic field

• A high-voltage spark produces free electrons• Free electrons are accelerated by electric field• Accelerated free electrons produce high energy

collision and ionization of Argon gas• Self-sustaining plasma is formed at open end of

quartz torch

Processes in the Plasma

Recombination ← Ionisation ← Atomisation ← Vaporisation

Oxides ← Ions ← Atoms ← Gas ← Solid ← Liquid

Sampleaerosol

M(H20)+ X-MXnMXMXM+MO+

Interface:Ion Sampling

TURBO-MOLECULAR PUMP

VACUUM PUMP

SAMPLER CONE

SKIMMER CONE

PLASMA

ZONE OF SILENCE

INTERFACE~5 Torr

ATMOSPHERE 760 Torr

ROTARY

ION OPTICS ~1x10-4 Torr

19

ICP-MS Cones Sample Ions from the Plasma

• Sampler Cone• Plasma encounters this cone first

• Skimmer Cone• Located behind the sampler cone

The Mass Spectrometer• Responsible for the high sensitivity of ICPMS instruments.• Separates ionized species on the basis of their mass to

charge ratio.• Requires high vacuum (~ 10-6 Torr) to operate• Resolution must allow detection of low concentration

elements in presence of adjacent high concentration elements.

• Scanning speed must be fast enough to cope with transient signals from various sample introduction systems

• Must accept a wide distribution of ion energies

Mass Spectrometer:Common Mass Analyzers

• Quadrupole

• Ion Trap

• Time of Flight

• Double-Focusing Magnetic Sector

Mass Spectrometer:Quadrupole Mass Analyser Schematic

Only one mass has a stable trajectory

Vacuum System: Turbomolecular Pumps

Rotary Pumps

Element Name

Element Symbol

Element Symbol

Element Symbol

Arsenic As Lithium Li

Barium Ba Manganese Mn

Beryllium Be Mercury Hg

Bismuth Bi Nickel Ni

Cadmium Cd Rubidium Rb

Cesium Cs Selenium Se

Chromium Cr Silver Ag

Cobalt Co Strontium Sr

Copper Cu Thallium Tl

Gallium Ga Uranium U

Indium In Vanadium V

Lead Pb Zinc Zn

Elements analysed by ICP-MS in ARD

Analysis of Samples by ICP-MS

• Follow BCSIR SOP – 22 • Prepare tuning solution• Prepare standard solution of metals of different

concentrations• Always use de-ionized water having a resistivity of

17.5–18.5 MΩ/cm • Use suprapure ICP-MS grade acids

Seven Elements of Quality Control during sample analysis by ICP-MS

• Certification of operator competence• Calibration• Analysis of externally supplied standards• Analysis of blanks• Analysis of duplicates • Recovery of known additions• Control charts

The End