Trace Evidence Analysis Facility

Instruments

• PE Elan DRC II ICP-MS (Quadrupole)

  The ELAN DRC Inductively Coupled Plasma Mass Spectrometer (ICP-MS) analyzes minor and trace elements of solutions, solids, and gases by atomic mass spectrometry. More than 70 elements can be measured. The typical sensitivity of the ICP-MS is ng/L (ppt) and less than 3 minutes for rapid multi-element capability. Since the early 1980s, numerous scientists have demonstrated the relevance of the application of ICP’s methods to conduct an elemental analysis of several samples.

  In general terms, ICP instruments are composed of three main parts: the sample introduction system, the ionization source, and the detector. The plasma reaches high temperatures (5000-10000K) at which the sample becomes desolvated, atomized, excited and ionized. The ions formed can travel into a mass selective detector for analysis.
  
  This ICP-MS instrument can be coupled to laser ablation systems to conduct a direct analysis of solid materials without requiring previous chemical digestion.

• Thermo ELEMENT2 HR-ICP-MS (High Resolution Sensor Field, NSF Funding)

  The Thermo ELEMENT2 Inductively Coupled Plasma Mass Spectrometer (ICP-MS) is similar to the ELAN DRC II above, except that it has a high-resolution sector field mass analyzer with three different slits that control the width of the ion beam. Therefore three mass resolutions are available: low (300), medium (4000), and high (10,000), that can be used to resolve most interferences. In addition, the low resolution mode is more sensitive than a quadrupole, resulting in sensitivities in the pg/L (ppq) range.

  This ICP-MS instrument can be coupled to laser ablation systems to conduct a direct analysis of solid materials without requiring previous chemical digestion.

• Laser Ablation

  Laser ablation (LA) systems are available as a sample introduction system for the ICP-MS, HR-ICP-MS, and ICP-OES.

  Laser ablation is a state-of-the-art sample introduction technique that has simplified the analysis of solid materials. Laser ablation ICP-MS possesses several key features that provide a tremendous potential for its application to forensic and material analysis, such as requiring minimum sample preparation and sample consumption (< 250 ng), eliminating the need for complex procedures and handling of hazardous materials for the digestion of samples, permitting the detection of major, minor and trace elements with high precision and accuracy, reducing the risk of contamination and polyatomic interferences associated with aqueous solutions.

  Laser ablation has been thoroughly evaluated since the 1990s; more than 100 papers have been published, including applications and improvements in designs of the laser systems. Typical samples include glasses, coatings, metals, powders, ceramics, geological materials, alloys, biological materials, and polymers.

  A typical LA-ICP-MS setup consists of a laser, a sample cell and the ICP-MS, which is used as an ionization source and analyzer. A solid sample is placed inside the ablation cell and a laser beam is focused on the surface of the sample. When the laser is fired, the high-energy interaction between the laser and the sample surface produces a cloud of very small particles and micro-droplets. These particles are removed from the sampling cell by a carrier gas, usually argon or helium, and are swept into the ICP plasma for atomization, ionization and subsequent analysis. The laser ablation software program controls all laser parameters, sample viewing, stage positioning and gas routing functions, including triggering of the mass spectrometer, for a fully automated ablation process. Ablation patterns can include spots, lines or raster scans.

  Our facility has three laser ablation systems:

  • The Applied Spectra J200 Tandem (266 nm)
    • The Applied Spectra J200 is a 266nm laser ablation system with built-in broadband spectrometers that allows for simultaneous ("tandem") laser-induced breakdown spectroscopy (LIBS - see below) analysis during laser ablation, which expands the elemental menu. The J200 can also be operated in laser ablation mode alone or LIBS mode alone. The J200 has the largest sample cell of the three systems, which allows more flexibility for large samples.
  • The New Wave UP 213 (213 nm)
    • UP-213 is the 2nd generation, high-performance Nd:YAG deep UV (213nm) laser ablation system that provides flat craters and high absorption for the analysis of opaque and transparent materials alike. The deep UV 213nm wavelength produces a finer particle distribution. This increases transport efficiency of the aerosol resulting in better sensitivities and minimal deposits at the plasma.
  • The CETAC LSX-500 (266 nm)
    • The LSX-500 features a compact Nd:YAG laser that delivers 266 nm. It has different sample cell components to accommodate several sample shapes and sizes. The flat beam profile of this system minimizes elemental fractionation.
• JEOL JSM 5900LV high and low vacuum scanning electron microscope with an EDX & XRF

  The scanning electron microscope (SEM) produces enlarged images of a variety of specimens, achieving magnifications of over 100,000X. This important and widely used analytical tool provides an exceptional depth of field, minimal specimen preparation, and the ability to combine the technique with X-ray microanalysis.

  Electrons striking the specimen react with the atoms of the sample surface and produce three types of signals: X-rays, electrons, and photons. The main detector system picks up the electrons, amplifies them and converts them into electrical voltage. The scan generator signal, fed to the deflection system of the column, moves the beam in a raster pattern over the specimen area. At approximately the same time the monitor for viewing the image is also scanned. The electrical voltage changes as it rasters, which provides serial information of the specimen surface. This signal, modulated by the one from the detection system, produces a theonscreen image.

  The other detectors include: back-scatter detector, secondary electron detector, CCD camera and energy dispersive X-ray (EDX) detector. The EDX detector is capable of measuring light elements. An X-ray source is also available, allowing X-ray fluorescence spectroscopy (XRF) analysis, which is capable to measuring heavier elements.

  The instrument also has the capability of working in low vacuum mode, which eliminates the need to coat non-conductive samples and image wet samples for preliminary imaging or imaging at low magnification. An Anatec Ltd., Hummer 10.2 gold sputtering system is available to coat non-conductive samples for enhanced imaging at high magnification.

• PE Optima 7300 DV ICP-OES with dual view (axial and radial)

  The PE Optima 7300 DV ICP-OES instrument is capable of quantitative analysis of more than 73 elements. This instrument has a higher throughput (more samples per hour) and hence a lower cost per analysis than the ICP-MS system. The sensitivity of ICP-OES is ~ 10-100 lower than ICP-MS but ICP-OES has a higher tolerance for high matrix level samples without sample dilution. With its dual viewing of the plasma and two solid- state detectors (one for UV, one for Vis), the PE Optima 7300 DV offers good detection limits and true simultaneous measurements and is ideal for moderate to heavy loads of difficult samples.

• Laser-Induced Breakdown Spectroscopy (LIBS) system

  We have two commercial systems from Applied Spectra:

  • J200 (1064 nm, Aurora 6-channel broadband spectrometer with CCD detector, Andor Mechelle high-resolution broadband spectrometer with Andor iStar ICCD detector, removable closed cell stage with Ar or He gas input, capable of simultaneous laser ablation and LIBS
  • J200 Tandem (266 nm, Aurora 6-channel broadband spectrometer with CCD detector, Andor Mechelle high-resolution broadband spectrometer with Andor iStar ICCD detector, removable closed cell stage with Ar or He gas input, capable of simultaneous laser ablation and LIBS)

  
  

  We also have open customizable LIBS systems with the following components:

  Lasers: nanosecond pulsed Nd:YAG

  • NewWave Solo PIV 1064 nm
  • Big Sky Ultra 1064 nm
  • Brilliant b 532 nm
  • New Wave Tempest 266 nm

  
  

  Spectrometers:

  • Andor Mechelle high-resolution broadband spectrometer with Andor iStar ICCD detector
  • Applied Spectra Aurora 6-channel broadband spectrometer with CCD detector
  • Princeton Intruments PI-MAX Czerny-Turner high-resolution spectrometer with ICCD detector

  
  

  Accessories:

  • Berkley Nucleonics delay generators
  • Oscilloscope
  • CCD cameras
  • Motorized stages
  • Vernier stages
  • Lenses and mirrors for 266, 532, and 1064 nm
  • Multimode fiber optics
  • Labview
  • Two large breadboard tables
• Optical Microscopes
  • Stereomicroscopes with digital cameras (measurement of lines and area)
  • Polarized light microscope (PLM)
  • Foster and Freeman Glass Refractive Index Measurement (GRIM2) system
  • Keyence Digital 3D microscope (depth profiling, measurement of lines, area, and volume, 3D mapping)
• Sample Preparation
  • MM200 Ball Mill with tungsten carbide or PTFE jars and balls for milling and homogenizing solid samples
  • Carver Bench-Top Pellet Press with stainless steel pellet dies (13 mm and 6 mm diameter)
  • AirClean Clean hood
  • Ultrasonic bath
  • Ovens
  • Hot plates
  • Vortex mixers
  • Centrifuges
  • Sieves (mini metal sieves, disposable plastic sieves)
  • Pipettes (micropipettes, serological pipettes, digital pipettor)
  • Environmental Express Hot Block for open vessel digestions
  • Milestone Ethos UP for microwave-assisted digestion