ICP-MS is an analytical technique that combines an inductively coupled plasma source with a mass spectrometer to detect elemental ions. The ICP source converts atoms in a sample to ions at very high temperatures, which are then separated and detected based on their mass-to-charge ratio in the mass spectrometer. ICP-MS provides excellent detection limits and precision for elemental analysis and can detect many elements simultaneously while also allowing for isotopic analysis. The technique requires high vacuum and specialized components to generate the plasma, transmit ions into the mass spectrometer, separate ions by mass, and detect them.

1. In-house Training on ICP-MS

2. 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.

3. 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

4. Comparison of Techniques ICP-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

5. ICP-MS Components • Sample Introduction • Plasma Generation • Interface • Ion Optics • Mass Analyzer • Vacuum System

6. • Sample Introduction Delivers finely divided sample (usually aerosol) to plasma • Plasma Source Ion Source Ar plasma 10 000K • Interface Allows transfer of atmospheric pressure ion source to high-vacuum mass analyser

7. Ion Optics Focuses ion beam and helps eliminate neutral species and photons • Mass Analyzer Separates and measures individual ions by mass • Vacuum System Provides low pressure environment for mass spectrometer to operate effectively (no collisional losses) Enables transition from plasma to high-vacuum via interface region

8. The Detector Converts ions into electrical pulses Magnitude of the electrical pulse is proportional to the number of ions in sample

9. 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

11. How is a Plasma formed?

12. Sample Introduction System Low uptake concentric nebulizer standard External spraychamber Double pass glass spray chamber Room temperature to -15º C Moves with torch Three channel peristaltic pump Computer controlled Smart Rinse enabled for optimized rinseout

13. 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

14. ICP-MS Torch

15. 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

16. Processes in the Plasma Recombination ← Ionisation ← Atomisation ← Vaporisation Oxides ← Ions ← Atoms ← Gas ← Solid ← Liquid Sample aerosol M(H 2 0) + X- MXn MX MX M+ MO+

17. ICP: Why are there four gas flows? Auxiliary Flow holds plasma away from torch/injector tube prevents torch melting Plasma Flow forms the plasma Nebulizer Flow punches cooler channel through centre of plasma carries sample Sheath Gas (some ICPMS instruments) Allows control of the velocity of the center channel independent of the sample delivery rate

18. 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

20. 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

21. Mass Spectrometer: Common Mass Analyzers Quadrupole Ion Trap Time of Flight Double-Focusing Magnetic Sector

22. Mass Spectrometer: Quadrupole Mass Analyser Schematic Only one mass has a stable trajectory

23. Vacuum System: Turbomolecular Pumps

24. Rotary Pumps

25. Elements analysed by ICP-MS in ARD 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

26. 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

27. 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

28. The End