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