ICP-OES
Instrumental Analysis of Beryllium Particulates
Whitney Coffey
ICP-OES…?
Inductively Coupled Plasma-Optical Emission Spectroscopy
Overview
Properties of beryllium
Industrial uses of beryllium
Health risks
Sampling methods
Instrumental analysis (ICP-OES)
Physical Characteristics
of Beryllium:
Atomic Number: 4
Atomic Weight: 9.012
Solid at room temperature
Period Number: 2
Group Number: 2
Group Name: Alkaline Earth Metals
Good thermal conductor
Good electrical conductor
Non-magnetic metal
Melting Point: 1560 K
Boiling Point: 2744K
Density: 1.85 g/cm3
Extremely lightweight, yet very
stiff
Sources of Beryllium:
Found in approximately 30 mineral species; the most significant sources are beryl
and bertrandite
Aquamarine and emerald are precious forms of beryl
Beryllium has many industrial uses.
These include:
Aerospace
Space shuttle components
Structural material for high-speed aircraft and missiles
Atomic Energy
Nuclear weapons components
Nuclear reactor components
Ceramics
Crucibles
Ignition modules
Jet engine blades
Semi-conductor chips
Electronics
Computer parts
Telecommunication parts
Transistors
Metallurgy
Aluminum-, copper-, magnesium-, and nickel-beryllium alloys
So why analyze for beryllium particulates?
Beryllium-related health issues
Beryllium Related Health Risks
Beryllium is safe in natural state and in finished products
Beryllium dust or fumes are unsafe, and can cause illness:
Lungs primarily affected
Other organs may also be affected
1 related condition:
Beryllium Sensitization
2 beryllium-related illnesses:
Chronic Beryllium Disease
Acute Beryllium Disease
Beryllium Sensitization
Immune response:
After an individual inhales beryllium dust or fumes, the immune system may
see the element as a foreign invader
Cells accumulate in the bloodstream, prepared to mount an attack against
any beryllium particles encountered
No outward symptoms
Diagnosis:
BeLPT test (beryllium lymphocyte proliferation test):
Blood test to identify immune response to beryllium
Highly specific – beryllium only cause of immune response
Normal result: rules out beryllium sensitization as well as CBD
Chronic Beryllium Disease (CBD)
Scarring of the lungs that results from immune system
attacking foreign beryllium particles
Symptoms:
Shortness of breath during activity
Persistent dry cough
Fatigue
Chest and joint pain
Increasing loss of appetite
*Symptoms can take a decade or more to develop
Diagnosis:
Abnormal BeLPT test
Further testing, including:
Chest x-ray
Pulmonary function testing
Blood work
Exercise tolerance testing
Bronchoscopy with possible biopsy
Acute Beryllium Disease (ABD)
Caused by high dose exposure to dust or fumes
Common symptoms:
nausea
fatigue
night sweats
cough
breathing difficulties
Onset of symptoms is usually immediate, occasionally delayed a
few days following exposure
Cases of acute beryllium disease have become quite rare, thanks
to improved safety procedures in the workplace
Beryllium sampling methods
Two general sampling methods are currently in use:
Air sampling
Wipe sampling
Air Sampling
A measured volume of air is
drawn through a filter - inhalable
dust sampler
Filter and any collected sample
then digested and prepared for
instrumental analysis
Air sampling rates are typically
identified in liters per hour
Wipe Sampling
Method for sampling smooth
surfaces
Analyst can choose appropriate
size for the sampling area per
wipe
cm2 is a suitable frame of
measurement
Two methods:
Dry wipe sampling
Wet wipe sampling
Dry Wipe Sampling
May be required for some surfaces that:
Can be damaged or compromised by moisture
Can be damaged by specific compounds used to moisten the wipes
*Cautionary note:
Dry wipes remove only a fraction of the residue from a surface as wetted
wipes do - if wetted wipes can be used without compromising
the
sampling surface, they are the preferred choice.
Wet Wipe Sampling
Moistened wipes remove greater percentage of residues than dry wipes
Wipes typically moistened with:
Distilled water
Methanol
methanol-wetted wipes have proven most efficient
* In any of the above methods, the collected samples are subjected to an acid
digestion, resulting in a liquid sample that can be analyzed via ICP-OES*
ICP-OES
Brief definition
Instrument components and functions
Particulate Analysis
Spectral interferences
MSF: correction software for spectral interferences
What is ICP-OES?
ICP-OES, or inductively coupled plasma optical emission spectroscopy, is a multielement technique featuring:
Moderately low detection limits (~0.2-100ppb)
Variety of sampling options for organic or liquid matrices
Ability to run up to 60 samples in a single run time of <1min
Few chemical interferences
Some spectral interferences that can be corrected via software
ICP source for more complete dissociation of samples
Basic function of ICP-OES:
Atoms of the sample in the ICP plasma emit photons
Photons of each element have characteristic wavelength
Photon emission recorded by optical spectrometer
Photons emission calibrated against standard emissions
Provides quantitative results of sample
Process Overview
Sample typically injected as a liquid (solid samples prepared via acid digestion)
Nebulizer converts liquid sample into an aerosol
Spray Chamber transports aerosol sample to the plasma torch
Plasma torch vaporizes, atomizes, and ionizes aerosol sample
Transfer Optics focus plasma image onto entrance slit of spectrometer
Wavelength dispersive device of the spectrometer isolates proper emission line
Detector and its components measure intensity of the emission line
Computer software compiles data, produces spectral plots of data
Nebulizer
The nebulizer converts the liquid sample into an aerosol
Aerosol is then transported to plasma torch via spray chamber
Aerosol droplets must be very small:
Prevents clogging of apparatus
Provides complete desolvation of sample for accurate results
Nebulizer partly responsible for droplet size
Pneumatic nebulizers most common:
to create an aerosol, pneumatic nebulizers rely upon high-speed gas flow
Peristaltic Pump
Sample solution pumped into nebulizer by peristaltic pump
Solution is pushed through tubing via process called peristalsis:
Series of rollers push solution through tubing
Only tubing comes in contact with solution
Prevents contamination of sample by the pump
Tubing material varies with types of samples being analyzed
Flow rate of solution into nebulizer is fixed by peristaltic pump
Spray Chamber
Spray chamber is placed between nebulizer and torch
Primary function is to remove droplets too large to pass through torch
Typically allow droplets no larger than 10 m in diameter to pass through
~1-5% of sample will be passed to torch
~95-99% drains into waste container
Spray chambers usually made of corrosion-resistant material, to withstand
hydrofluoric acid and corrosive organics
ICP Plasma Source
Definition: a plasma is an electrical conducting gaseous mixture
containing considerable concentrations of electrons and cations – net
charge approaches zero
Argon plasma most commonly used
ICP plasma source frequently referred
to as a torch
Basics of the ICP source:
ICP consists of 3 concentric quartz tubes
Argon gas streams through quartz tubes:
Carries sample through central tube
Also spirals around wall of outer tube:
Centering plasma radially
Cooling inside walls of center tube
Water-cooled induction coil:
Surrounds top of outer tube
Powered by RF generator
Produces fluctuating magnetic field
Ions and electrons interact with magnetic field
Interaction causes flow of particles
Plasma:
Very intense, white, nontransparent core topped by a tail
Core extends a few mm above quartz tubes
Results from recombination of argon and other particles
Optically transparent tail 10-30mm above core
Tail resembles a flame
Spectra typically obtained 15-20mm above induction coil
Transfer Optics:
ICP radiation usually collected by a focusing optic, typically a
convex lens or concave mirror
Optic focuses image of the plasma onto entrance slit of
spectrometer or wavelength dispersive device
Transfer optics can analyze in three general modes:
Radial (side-on) view
Axial (end-on) view
Dual view
Wavelength Dispersive Device
Differentiates emission radiation of the elements and molecules
Emission radiation is sorted by wavelength
Common dispersing device: combination of echelle grating and prism
Echelle grating
Separates radiation by wavelengths
Produces multiple overlapping spectral orders
Prism
Separates the overlapping orders into 2-dimensional pattern
Pattern called ‘echellogram’
Selected emission line transmitted to the detector.
Detector
Measures intensity of emission line
Many types of detectors to choose from
Newest innovation is SCD  segmented-array charge coupled device detector
SCD houses individual collections of small subarrays
20 to 80 pixels each
Over 200 subarrays on a silicon wafer
2D pattern of subarrays associated with echellogram produced
Subarrays account for over 236 ICP spectral lines
Spectral lines correspond to the 70 elements ICP analyzes
Good response to light 160-782nm
Computer
Detector transmits emission intensities to computer
Computer software compiles, stores, and displays data
Emission results for each element
Spectral plots of individual samples
Spectral overlay plots
Software can correct for a variety of spectral interferences
Particulate Analysis
70 elements can be analyzed via ICP-OES
Detection limits vary for each element
Acid digestion of solid sample creates aqueous solution
Aqueous sample injected into ICP
Inner argon flow rate of 1L/min
Standard and sample solutions typically delivered at rate of 1mL/min
ICP-OES analyzes emission abundance of sample ions
Computer generates spectral plot on monitor
Amount of solution required varies
Number of elements being determined
Number of replicate measurements being taken
Speed of instrument
ICP-OES detection limits
Copyright © Jobin-Yvon Emission 2000
Beryllium Particulates
ICP-OES LOD for beryllium < 1ppb
DOE sets beryllium baseline at 0.004ppm for analyses
Beryllium crustal abundance 1.6ppm: above this considered “hit”
Wavelengths for beryllium analysis:
Be313.042
Be313.107
Subarray used for beryllium analysis:
312.968 – 313.180
Computer plots spectrum of emission abundance for beryllium ions in subarray
Calibration blank run with sample
In specified subarray:
2 hydroxyl peaks
1 argon peak
2 beryllium peaks
Spectral Interferences
Several elements cause spectral interference in designated subarray:
Zirconium
Vanadium
Cerium
Titanium
Niobium
Molybdenum
Chromium
Emission from these elements can hide emission abundance of beryllium,
producing false positives or false negatives
Standards of known concentration analyzed along with sample  MSF applied
Spectral Correction – MSF
Multi-component spectral fitting
Algebra-based software program:
Single-element spectra obtained for each interfering element
Concentration of analyte calculated using scaling factors
Scaling factors calculated using interfering single-element spectra
Spectral interferences mathematically eliminated
For accurate results, MSF software requires that data be collected in highresolution mode  peaks must be resolved at every 0.001nm
Typical soil sample at low resolution
Spectral overlay at low resolution
Spectral overlay at high resolution
Beryllium spectrum after MSF application
What have we learned?
Strong + lightweight + corrosion resistant = good for industry!
Fumes + dust = bad for lungs!
Conclusion? Find dust and remove it. But how do we find it?
Some instruments = poor LOD’s
Some instruments = too $$$$
ICP-OES = competitive LOD’s, reasonable cost
Sources
National Jewish Medical and Research Center: www.njc.org
Optima 5000 DV Series ICP-OES. www.perkinelmer.com
Boss, Charles B; Fredeen, Kenneth J. Concepts, Instrumentation, and Techniques in
Inductively Coupled Plasma Optical Emission Spectrometry, 2nd Edition. Perkin-Elmer.
1997.
Kriebel D, et al. The pulmonary toxicity of beryllium. Am Rev Respir Dis 1988; 137:464473.
Kreiss K, et al. Risks of beryllium disease related to work processes at a metal, alloy, and
oxide production plant. Occup Environ Med 1997; 54:605-612.
Nolte, Joachim. ICP Emission Spectrometry – A Practical Guide. Chapter 4; Method
Development. www.wiley-vch.de
Septon, Jerry; Abel, Ray; Simmons, Michael: Metal and Metalloid Particulates in
Workplace Atmospheres (ICP Analysis). OSHA Technical Center, www.osha.gov. Sept
2002.
Chris’ instrumental book