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Testing Jewelry with HDXRF


BACKGROUND

The ASTM Children’s Jewelry Safety Specification F2923–11 and the ASTM Adult Jewelry Safety Specification F2999–13 both establish requirements and test methods for specified hazardous elements in addition to other potential dangers like magnets and batteries. This application note demonstrates the power of HDXRF (High Definition X-ray Fluorescence) and its ability to screen and quantify lead, cadmium, nickel, and the remaining F963 regulated heavy elements in jewelry.

SIGNIFICANCE

Adult and children’s jewelry both have a specification for total lead content. All children’s jewelry materials including metal components, plastic, glass, etc. shall not exceed 100 ppm lead for substrates and 90 ppm for paint and other similar surface coatings with the exception of exempt materials listed in Table 2 of ASTM Children’s Jewelry Safety Standard F2923-11; these materials include, but are not limited to, precious metals, wood, textiles, and precious gemstones. HDXRF has been approved by CPSC (Consumer Product Safety Commission) for quantification of lead in homogeneous substrates, and it’s the only CPSC-approved alternative to wet chemistry for quantification of lead in paint and similar surface coatings. Lead limits for adult jewelry are higher than 100 ppm and allow for as much as 1.5% lead in unplated metals. For a complete list of substrate materials and corresponding lead limits, see Table 1 in the ASTM Adult Jewelry Safety Specification F2999–13.

All accessible metal or plastic/polymeric components of children’s jewelry should be screened for total cadmium content according to ASTM F2923-11. Materials containing 300 ppm or less total cadmium do not need to be tested further for migratable cadmium, and materials containing more than 300 ppm total cadmium must be further tested with a substrate appropriate method for migratable cadmium. Adult jewelry, accessible metal or plastic/polymeric components must be screened for total cadmium content as well. In accordance with ASTM F2999–13, the total cadmium content screening limit is 1.5%.

Metal components of children’s jewelry must meet migratable nickel limits. Regarding sensitivity to nickel or the limited potential of nickel to be released from metal components of adult jewelry, representations should be made based on reasonable and representative tests suitable for the application HDXRF can detect the presence of Ni down to 10 ppm and, therefore, can help to determine which components require testing for migratable nickel and which do not.

Additionally, HDXRF has the ability to screen for all of the regulated F963 elements in surface coatings as well as homogeneous materials. In accordance with the F963 directive, if an appropriate method is used for total content of all eight regulated elements and the results are below soluble limits for each element as prescribed in the method, the material can be considered to conform to requirements without further testing. Unlike wet chemistry, HDXRF is non-destructive, yields fast and precise results with minimal training, and can be conducted on-site (at a factory or in a warehouse). HDXRF allows for separate and simultaneous analysis of coatings and substrates for more than 30 elements, including antimony, arsenic, barium, chromium, mercury, and selenium

METHODOLOGY

A sampling of standard reference materials as well as actual children’s jewelry were measured with HDXRF. Each sample or sample area was measured 10 times and the average of the measurements was reported. All elemental concentrations in this report are presented in ppm.

RESULTS

BCR®-355, ERM®-EC681k, and ERM®-EC680k (left):

Prior to taking measurements, the surface of BCR®-355 was sanded lightly to ensure that there was no oxidation on the sample, and the polyethylene certified reference materials were heated and pressed into discs. See results in Table 1 and Table 2.


Table 1
Zn355 Certified Measured with
HD Mobile
Standard
Deviation
Pb 56.9 ± 1.9 59.2 7.0
Cd 58.1 ± 0.4 57.4 9.6

Table 2
Pb Cd Cr As Hg Sb
681k Certified 98.0 ± 6.0 137.0 ± 4.0 100.0 ± 5.0 29.1 ± 1.8 23.7 ± 0.8 99.0 ± 6.0
Measured with HD Mobile 99.0 ± 1.0 130.0 ± 7.0 110.0 ± 2.0 35.5 ± 1.4 29.0 ± 2.7 85.5 ± 9.0
680k Certified 13.6 ± 0.5 19.6 ± 1.4 20.2 ± 1.1 4.1 ± 0.5 4.64 ± 0.2 10.1 ± 1.6
Measured with HD Mobile 12.9 ± 0.5 19.8 ± 1.4 20.5 ± 0.6 4.4 ± 0.6 3.9 ± 0.4 36.2 ± 7

RESULTS

Locket (left):When taking a measurement of a plated sample through the surface plating, the result will be elementally biased towards the plating. However, XRF (X-ray Fluorescence) can still be a powerful qualitative tool to see where elements of concern are being used in the manufacturing process. For example, the locket pictured here has two platings on an iron substrate; a copper alloy and a nickel alloy surface plating. See results in Table 3.


Table 3
Cr Cd Cu Fe Ni Ag Zn Pb
Nickel Surface Plating 327 ND<6.0 516,506 217,020 256,612 772.0 159.0 7.0
Copper Alloy Plating 198 ND<5.2 834,379 162,865 355 ND<5.0 ND<56.0 3.5
Iron Alloy Base 3,840 ND<5.5 1,533 989,219 1,415 ND<5.7 8.8 125.0

CONCLUSION

HDXRF technology can be used as a tool for screening and quantifying many regulated elements including lead, cadmium, nickel, and other F963 elements non-destructively with a single test. The same high level of precision is achieved for both metal and plastic materials, and qualitative metal plating analysis gives users the ability to pinpoint what areas of their product need additional testing to ensure safety and compliance.