DEVELOPMENT OF PAINT REFERENCE MATERIALS FOR ANALYSIS OF LEAD IN CHILDREN’S TOYS

 

John L. Molloy1, David Cobb2, and John R. Sieber1

 

1 Analytical Chemistry Division, CSTL, NIST Gaithersburg, MD 20899

2 CPSC, Gaithersburg, MD 20878

 

Congress passed the Consumer Products Safety Improvement Act in 2008, lowering the allowable limits of Pb in paint and substrate materials in children’s products to 90 mg/kg.  While these limits start to go into effect later this year, proper enforcement of the regulations will be difficult due to the problem of measuring the sheer volume of products produced and imported into the United States.  One feasible method is to quickly screen many samples and send possible noncompliant samples for further, time-intensive analysis.  A technique of quickly and effectively screening sample involves the use of handheld X-ray fluorescence (XRF) instruments.  Unfortunately, partially due to the lack of available reference materials, the performance of such devices is unknown across the wide variety of paints and substrates.  In collaboration with the Consumer Product Safety Commission, NIST has undertaken a study of the ability of current XRF technology to analyze Pb-containing coatings and an investigation of appropriate reference materials containing Pb near the regulatory limits.

         NIST has produced paint reference materials in the past, such as SRM 2579a, which was targeted at mitigation of Pb paint in houses.  However, these reference materials covered levels of Pb two to three orders of magnitude higher than limits for children’s toys, pushing the limits of many handheld XRF instruments.  The problem of measuring Pb in coatings such as paint is compounded by the wide variety of paint types used and drastically different substrates such as wood, plastic, and metals.  The substrates, governed by a different set of regulatory levels, may also contain Pb, leading to the problem that fluorescence from the Pb present must be separated from that produced by the substrate versus that produced by the paint coating.  In many cases, paint layers on such items are well below 100 µm in thickness, with high variability across a toy’s surface.  This work shows examples of analysis of Pb-containing paint layers by XRF, with discussion of some of the spectroscopic, material, and other complexities that must be overcome to ensure high quality reference materials are produced.

 

 


 

CATEGORY: Chemistry

 

Mentors Name: John R. Sieber

Division, Laboratory: 839, CSTL

Room, Building Mail stop:A347, Bld 227, Stop 8391

Tel: 301-975-4114

Fax: 301-869-0413

Email: john.molloy@nist.gov

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