kate mcintosh wadsworth center, nysdoh lcc workshop june 8, 2012
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Performance of current XRF instrumentation for measuring
the lead content of environmental samples
Kate McIntoshWadsworth Center, NYSDOH
LCC WorkshopJune 8, 2012
Outline
• Background• X-Ray Optical Systems and Monochromatic XRF (M-XRF)
• Lead in painted toys and consumer products• Instrumentation
• XOS HD-Prime • Thermo Scientific Niton XL3t
• Inter-laboratory study and reference materials• Lead in household paint
• Screening with the XL3t• Conclusions and summary recommendations• Future work
• XOS Personal Environmental Analyzer (PEA)
X-Ray Optical Systems
• Industry collaborator • Leader in development and
manufacture of x-ray optics• Interest in developing new
technologies for environmental applications
• Prototype instruments based on monochromatic XRF (M-XRF) for specific public health problems
• Advantages:• Reduced background provides
improved P/B and greater sensitivity
• No loss in intensity due to scatter in filter, so low power sources can be used
East Greenbush, NY
X-Beam®
Doubly Curved Crystal (DCC) optic
Lead in painted toys and consumer products
XOS HD-Prime
Dimensions: 36x26x32 inches Weight: 240 lbs
cameras
sample chamber
Calibration modes:Plastic, metal, wood,
glass, rubber, leather, textiles, bulk paint
For painted products:1) Measure painted region
2) Measure substrate
≤7 minutes1 mm spot
size
50 kV, 2 mA maximum Mo anode; 7, 17.5, 31 keV DCCs; SDD
Thermo Scientific Niton XL3t
• Purchased in 2009 to evaluate side-by-side with M-XRF
• Calibration modes• Metals (%)• Soil (mg/kg)• Filters (µg/filter)• Plastics (mg/kg)• Painted products (µg/cm2)
• Reports >30 elements
Dimensions: 9x9x4 inches Weight: <3 lbs
≤2 minutes
50 kV, 40 µA maximum Au anode; SDD
3-8 mm spot size
Lead in toysConsumer Product Safety Improvement Act (CPSIA) of 2008
• New regulations for products intended for children <12 years old
2 µg/cm2
Reporting units for lead in paint
• 90 mg/kg (ppm) is the CPSC limit required to demonstrate compliance with CPSIA• Basis in bio-kinetic model of lead exposure in children• Previous 600 mg/kg limit related to 300 µg Pb/day
expected to keep BLL <40 µg/dL
• 2 µg/cm2 is intended as a screening limit for small painted areas (<1 cm2 or 10 mg)• Industry consensus value, scientific basis uncertain• Appears widely used
• 2 µg/cm2 ≅ 90 mg/kg??
ASTM/XOS Interlaboratory Study - 2010 • Goal - precision statement for ASTM F2853, a standard
(CPSC approved) method for determination of lead in paint layers by M-XRF (HD-Prime)
• “Repeatability” 26 mg/kg at 90 mg/kg• “Reproducibility” 35 mg/kg at 90 mg/kg
• N = 9 labs: Wadsworth; NIST; 5 testing labs; Mattel; XOS• 40 test samples distributed
• Bulk substrate CRM/RMs• Metal, glass, wood, plastics
• Paint film on substrate RMs• 5 µm and 30 µm thickness
• Retain samples for further assessment
Painted-surface RMs on HD-Prime
Each of these samples
(n=10) ND with the XL3t,
5 false negatives
Error bars ±SD, n=10
Reference 50 mg/kgHD-Prime 52±6 (4% bias)
LOD (mg/kg) HD-Prime 17
Comparing XRF area concentrations with mass fractions determined by AAS
Error bars ±SD, n=10
30-µm paint on PVC
FP
Assessment with SRM 2569 Lead Paint Films for Children’s Products
Released by NIST in 2011Certified in both mg/kg and µg/cm2 units
Does not report in mg/kg
n=10
1.158 g/cm3
22.9 µm
LOD 16 mg/kg
LOD 0.03 µg/cm2 LOD 0.13 µg/cm2
Certified values in µg/cm2 are well below threshold
Non-representative matrix
Lead in household paint
Screening paint chips with the XL3t• Ex-situ XRF could provide an
alternative means of identifying LBP
• Preliminary assessment completed using NIST Powdered Paint SRMs and routine samples received at Wadsworth
n=7, 60 s measurement time
Samples measured as received in plastic bag
Screening paint chips with the XL3t
n=53 samples, 60 s measurement time
Conclusions & summary recommendations
• Determination of lead content in paint on toys is a very difficult analytical problem• (+) XRF nondestructive nature & ability to test small
areas/substrate• The XL3t is of limited use for determination of lead in painted
toys, given false negatives for non-PVC substrates• Shows promise for ex-situ identification of LBP
• Though the HD-Prime is approved for certifying compliance & reported no false negatives, quantitation at 90 mg/kg may be unreliable due to uncertainty in the “real world” LOD.
• CPSC should consider reducing the 2 µg/cm2 limit• NIST should produce SRMs more representative of painted toys • HUD/EPA should re-evaluate the 0.5 wt% limit as well as the
screening methodologies for LBP
Future Work
• Begin field evaluation of an M-XRF prototype intended for multi-element analysis • Characterizing the elemental content of
materials in personal environment is important for some public health studies as it helps identify possible sources of exposure
• R01 funding from NIH to incorporate into an ongoing epidemiological study
• Focus on toxic elements• Compare performance to existing technology• Sensitivity, accuracy, fitness-for-purpose
XOS PEA β-prototype
Large sample chamber
Dimensions: 15x18x18 inches Weight: 50 lbs
Touch screen
Pb, As, Hg, Cd, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, Br, Rb Sr, Ag, Sn, Sb, Ba, Au, Tl,
Bi
50 kV, 1 mA maximum Mo anode; 7, 17.5, 31 keV DCCs; SDD
4 minutes
Lead content in Indian spices
Error bars (XRF) ±SD, n=3, (ICP-OES & FAAS) ±10%, n=1
Chili powder
Screening in bag, PEA 130±9 mg/kg
30% bias
Turmeric
Screening of routine samples
Identified possible additional health risk (<5 min)
• Physician notified
Herbal medicine product submitted as part of a lead-
poisoning investigation
Error bars (XRF) ±SD, n=3, (ICP-OES) ±10%, n=1
Acknowledgements• Dr. Patrick Parsons, and the Laboratory of Inorganic
and Nuclear Chemistry (LINC) at the Wadsworth Center, NYSDOH
• John Orsini of LINC/NYSDOH• XOS• Funding: XOS SBIR from NIH NIEHS 5R44ES016689
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