Chem415 Quantitative Bio-Element Imaging Center (QBIC): Part II APRIL 13, 2015 DIRECTOR: PROFESSOR THOMAS V. O’HALLORAN MANAGING DIRECTOR: KEITH MACRENARIS, PH.D 1

Analytical Advantages of ICP over AA? 2

ICP is The Choice for Multi-Element Analysis 3

Component Breakdown of ICP Front End Integration For Liquid Samples: autosamplers coupled to peristaltic pumps For Separations/Speciation Analysis: Systems can be designed with GC, HPLC, IC or CE prior to integration into the ICP For Imaging: Laser ablation units can be integrate for quantitative elemental imaging/mapping Front End Integration For Liquid Samples: autosamplers coupled to peristaltic pumps For Separations/Speciation Analysis: Systems can be designed with GC, HPLC, IC or CE prior to integration into the ICP For Imaging: Laser ablation units can be integrate for quantitative elemental imaging/mapping Sample Introduction Nebuliser – Need to produce a fine mist for efficient sample introduction – Usually made of quartz or PFA – concentric, self-aspirating, and cross-flow Spray Chambers – Need to discern between large and small droplets from the nebulizer prior to introduction into the plasma torch – bead impact, cyclonic Sample Introduction Nebuliser – Need to produce a fine mist for efficient sample introduction – Usually made of quartz or PFA – concentric, self-aspirating, and cross-flow Spray Chambers – Need to discern between large and small droplets from the nebulizer prior to introduction into the plasma torch – bead impact, cyclonic Plasma Torch More efficient and reproducible vaporization, atomization, excitation, and ionization due to high temperatures of the plasma 6000 K K versus 3300 K for flames and furnaces Uses mainly argon as carrier gas an torch source so low noise or contamination due to electrode materials required in Flame AA or GFAAS Plasma Torch More efficient and reproducible vaporization, atomization, excitation, and ionization due to high temperatures of the plasma 6000 K K versus 3300 K for flames and furnaces Uses mainly argon as carrier gas an torch source so low noise or contamination due to electrode materials required in Flame AA or GFAAS Detection Optical Emission Spectrometer – Usually a echelle polychromator and CCD, CID, or CMOS detector chips Mass Spectrometer – Quadropole, Magnetic Sector Field, or Orbitrap with pulse counting and analog detectorsDetection Optical Emission Spectrometer – Usually a echelle polychromator and CCD, CID, or CMOS detector chips Mass Spectrometer – Quadropole, Magnetic Sector Field, or Orbitrap with pulse counting and analog detectors 4

Autosampler/Peristaltic Pump  Autosamplers: Usually come in a variety of configurations with multiple rack types  Peristaltic Pumps are typically used due to low cost and consistency  2 issues with peristaltic pumps: 1) with ICP-MS you have to average out the peristalsis. 2) sample contamination of tubing is difficult to remove (also known as memory artifacts)  Newer valve/syringe assemblies allow for auto-dilution and decrease uptake and washout times while increasing accuracy and precision  Even using new valve and syringe-driven autosampling peristaltic pumps are still required for waste and washout 5

Nebulizers  Nebulizers use 2 priniciple to create a fine mist for sampling:  1) Venturi effect whereby a fluid’s velocity must increase as it passes through a constriction  2) Pneumatic Induction whereby a gas is used as the driving force to convert a liquid into a fine spray  The main types of nebulizers used are concentric and burgener or enhanced parallel path nebulizers (usually for Highly corrosive samples such as HF) 6

Spray Chambers  Purpose of a Spray Chamber is to remove droplets produced by the nebulizer that are > 8 µm in diameter, smooth out pulses produced by the peristaltic pump, and if cooled keep the sample thermally stable  Two main types are double-pass and cyclonic spray chambers  Use correct material and choose proper design for particular sample types 7

Plasma Torch  Want to increase energy for more efficient atomization and ionization  ICP torches form the plasma by a tangential stream of argon gas flowing between 2 quartz tubes followed by pulsing AC of RF power through the coil producing an oscillating magnetic field (27.12 MHz usually)  An electric spark is applied to introduce free electrons into the gas stream which are then accelerated by the rapidly changing magnetic field  Accelerated electrons collide with argon atoms forcing the loss of an electron which in turn accelerate in the oscillating magnetic field  Results in multiple temperature zones within the produced plasma 8

ICP-OES Optics  After sample passes through the plasma the atom is allowed to drop from a high energy state back to the ground state through emission of a photon  These photons are analyzed through a monchromator and echelle grating before hitting the detector  Allows readouts in 2 dimensions providing better resolution and faster analysis than old PMT methods  Can get full spectrum analysis for every sample (called full frame capture) 9

ICP-OES: Axial versus Radial Viewing  Radial View: Off-axis plasma viewing provides highest upper linear ranges (~ 100 pm or greater depending upon intensity of spectral line)  Axial View: Views the light looking down the center of the torch providing better detection limits than radial view by up to 10-fold  Dual View: Allows viewing in both axes  Radial viewing is accomplished through a hole in the plasma torch allowing for faster transitions between axial and radial views (shorter run times) 10

Advantages and Disadvantages for ICP-OES Advantages  Due to high temperature of ICP plasma most species are broken into atoms or ions for excitation and subsequent emission  Of all analytical atomic spectrometry techniques has the fewest interferences  Can tolerate up to 20%-30% TDS  Multi-element capability due to CCD/CID chips Disadvantages  Prone to spectral interferences  Easily-ionize-element (EIE) effect – happens with elements with low ionization potentials such as alkaline elements which can suppress or enhance emission signals  Does not provide ultra-trace or real- time analysis  Does not provide information about the different naturally occurring isotopes of a particular element 11

ICP-MS  ICP-OES was commercialized in 1974, whereas ICP-MS wasn’t commercialize until 1983  Use Mass Spectrometer to analyze samples due to atomization and more importantly ionization of elements in the plasma  Singly charged ions are being detected according to there mass-to- charge ratio  Have to get the system into a low vacuum state between to Torr which is accomplished using a sample and skimmer cone interface 12

ICP-MS Detection: Cones 13 Sample Cone Skimmer Cone  Cones are generally made out of Ni: Robust, minimal interferences, tolerate high matrix, relatively long-lasting and realtively low cost  Can be made out of platinum: More resistant to corrosion, longer lasting, no Ni interference, cost 5-10 times more than Ni cones  Helps restrict the amount of sample going into the ion lenses and quadrupole and helps decrease the pressure incrementally

ICP-MS Detection: Lens Stack  Positioned between the skimmer cone and mass separation device  Consisting of multiple electrostatically controlled lens components  Steer the ions from the hostile environment of the plasma at atmospheric pressure and steer them into the mass analyzer at high vacuum  Ions with high kinetic energy will be transmitted in preference to ions with medium or low kinetic energy  Recent advancements have led to the design of a 90° lens prior to entry into the KED/CCT reaction cell or quadrupole 14

Quadrupole Mass Analyzer  Using a quadrupole mass analyzer consisting of 4 rods that are cm in length  Place a direct current on one pair of rods and a radio frequency field on the opposite pair ions of a selected mass are allowed to pass through to the detector while the others are ejected from the quadrupole  In the example 63 Cu is repeatedely scanned as electrical pulses are stroed and counted by a multichannel analyzer  Scan rates are typically 2500 amu per second and can cove the entire mass range of amu in about 0.1 s 15

Mass Interferences  Common interferences are argides, oxides, and chloride  Collision cell and reaction cell technology were developed to handle major mass interferences  Another solution is for high resolution magnetic sector field ICP-MS which is cost prohibitive 16

Advantages and Disadvantages for ICP-MS Advantages  Due to high temperature of ICP plasma most species are broken into atoms or ions for excitation and subsequent emission  Low level detection down to ppt  Isotope abundance determination  Large linear range due to multiple detectors PC and analog Disadvantages  Prone to mass interferences  Low tolerance for TDS usually < 0.5%  Difficult to analyze complicated matrices  More maintenance and associated cost 17

Laser Ablation ICP-MS 18

Information  For Microscopy and LA-ICP-MS Keith MacRenaris at  For STEM/EDS analysis Reiner Bleher at  QBIC website:  NUANCE website: