Slide 1 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 temper.
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 Techniques ICP-MS ICP-AES GFAAS FAAS Detection Limits Excellent Good Excellent Good Productivity Excellent Excellent Low Good 1-3% 0.3 – % 1–5% 0.1 – % Moderate Few Many Many Minimal Minimal Minimal Some Mass Effects High on low mass None None None Dissolved solids 0.1 – 0.4 % – 25 % Up to 20 % 0.5 – % 75 73 50 68 Sample Usage Low Medium Very Low High Isotope Analysis Yes No No No Skill required Easy Precision Chemical Interferences Ionization # Elements Method Development Running Costs Capital Costs Skill required Skill required High High Medium Low Very high High Medium Low ICP-MS Components •Sample Introduction •Plasma Generation •Interface •Ion Optics •Mass Analyzer •Vacuum System •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 •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 The Detector •Converts ions into electrical pulses •Magnitude of the electrical pulse is proportional to the number of ions in sample Steps Involved in ICP-MS •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 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 MO+ Oxides MX M+ ← Ions ← MX MXn M(H20)+ X- Atoms ← Gas ← Solid ← Liquid Sample aerosol Recombination ← Ionisation ← Atomisation ← Vaporisation Interface: Ion Sampling ZONE OF SILENCE SAMPLER CONE ION OPTICS ~1x10-4 Torr PLASMA SKIMMER CONE INTERFACE ~5 Torr TURBOMOLECULAR PUMP ROTARY VACUUM PUMP ATMOSPHERE 760 Torr ICP-MS Cones Sample Ions from the Plasma • Sampler Cone • Plasma encounters this cone first • Skimmer Cone • 19 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 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 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 ... 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