Analysis of Migratory Elements in Toy Samples Using ICP Spectroscopy

A number of high-profile cases concerning toys contaminated with heavy metals, such as cadmium, lead, and arsenic, have highlighted the importance of rigorous testing of toy product samples for toxic trace elements. Many of these elements pose substantial health risks if ingested by children, including damage to the central nervous system and even death. Product samples of all toys must be routinely analyzed for heavy metals in order to preserve public safety. However, a recent study from the Ecology Center’s Environmental Health Project and the Washington Toxics Coalition1 tested 1200 toy products and found that more than a third of all toys tested contained toxic elements, the most common being lead, mercury, cadmium, and arsenic. Of the objects tested, 17% contained more lead than is allowed by federal safety standards (600 ppm). Some products had lead levels more than five times the allowed maximum. Cadmium levels greater than 100 ppm were found in 2.9% of products, and arsenic levels greater than 100 ppm were found in 2.2%.

Heightened concern over the presence of toxic trace elements in toys highlighted the importance of selecting a method of analysis that can provide fast, accurate, and reliable results in order to ensure regulatory compliance. Many international regulations are largely based on a test method that monitors the levels of trace elements, which can migrate from a toy material into acidic solution. This is designed to simulate the release of certain elements when toy components are ingested by a child.

Analytical test methods

Table 1    -    Limits of element migration from toy materials according to ASTM F963-08 Part 3 (all values are mg/kg in solution)

The two most common test methods used are EN71 Safety of Toys—Part 3: Migration of Certain Elements2 and ASTM F963-08 Standard Consumer Safety Specification for Toy Safety.3 The maximum permissible concentration of the migrated elements is the same for both standards, as shown in Table 1

These values are based on the bioavailability of the elements and the average quantities of toy components that are inadvertently consumed by a child on a daily basis (estimated at 8 mg per day). Both methods require the testing of each component and each color of the toy as a unique sample. Metals are extracted from the toy component using dilute hydrochloric acid for 2 hr at 37 °C, and the solution is then analyzed, typically using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Other analysis methods can also be used for this application, such as atomic absorption spectroscopy, but due to its multielement capabilities ICP-OES is ideally suited to this type of analysis.

In plasma emission spectroscopy, a sample solution is introduced into the core of inductively coupled argon plasma at a temperature of approximately 8000 °C. At this temperature, all elements become thermally excited and emit light at their characteristic wavelengths. This light is collected by the spectrometer and split by a prism and a diffraction grating into its constituent wavelengths. Within the spectrometer, the light is then collected by wavelength and amplified to yield an intensity measurement that can be converted to an elemental concentration by comparison with calibration standards.

Typically, the use of ICP-OES systems requires complex instrumentation, and therefore highly skilled laboratory staff are needed to carry out the analysis process. However, the use of integrated software in combination with innovative ICP-OES hardware design can remove this costly requirement and provide analysis-ready method templates to simplify method development and enable simple “out-of-the-box” analysis, with little or no requirement for method development. Intelligent software tools can also be used effectively to simplify the instrument optimization process, negating the need for the user to set parameters and perform manual system optimizations. Electronic systems can also be used alongside ICP-OES, and transfer to a LIMS can help eliminate data transcriptions and human errors that may occur when using other techniques.

This article highlights the powerful analytical capabilities of ICP emission spectroscopy to determine migratory elements in toys using the Thermo Scientific iCAP 6200 ICP spectrometer and iTEVA instrument software (Thermo Fisher Scientific, Cambridge, U.K.).

Experimentation

The iCAP 6200 ICP spectrometer was used for the analysis. The dual-view, compact ICP instrument achieves sensitive analyte detection and provides a highly cost-effective solution for routine analysis of liquids in laboratories with standard sample throughput requirements.

Method

Three toy materials were analyzed from a small toy car and a baby’s rattle. These were sampled as follows:

  • Orange unpainted rubber body of a toy car (sample 1)
  • Unpainted blue wheels of a toy car (sample 2)
  • Sections of yellow plastic from a baby rattle (sample 3).

All of the samples were prepared in accordance with ASTM F963-08 and EN71 Part 3, as follows. A portion of the sample (a minimum of 0.1 g) was immersed in 0.07 mol/L hydrochloric acid (50 times the mass of the sample) and agitated in the dark at 37 °C for 1 hr, followed by 1 hr in the dark at 37 °C without agitation. All solid material was removed from the sample by filtration using a membrane filter. The remaining filtrate was analyzed immediately. A spike of each sample was also prepared to check recovery in the matrix. This was added to the relevant sample prior to agitation.

Standard preparation

Table 2    -    Concentrations of the standards prepared as recommended by the method template (all values are in mg/kg)

Standards were prepared by diluting 1000 mg/kg aqueous single-element standards to the concentrations listed in Table 2. The concentrations of the standards are reflected in the preloaded iTEVA method template. All standards were prepared to contain 0.07 mol/L hydrochloric acid. 


Table 3    -    Parameters used for the analysis

Method development

The EN71 Toy Analysis method template was opened in iTEVA. The standard sample introduction kit was chosen for the analysis as recommended by the method, and the instrument was calibrated and samples analyzed in a single run (Analysis A). Reanalysis of the identical samples was also performed the following day to simulate a typical sample analysis regime (Analysis B). Analysis parameters used by the method template are shown in Table 3.

Results

Table 4    -    Results of the sample analysis (Analysis A) with method detection limits and spike recoveries

The results of the analysis are shown in Table 4. The table also notes the plasma view (axial or radial) with which each wavelength was analyzed. A method detection limit (MDL) study was carried out by analyzing a 10-replicate, acid-matched blank. The standard deviation of the 10 replicates was multiplied by 3 to determine the method detection limit.

Table 5    -    Results of the sample spikes from two different analyses (Analysis A and B compared)

Of the samples analyzed, all of the toxic elements were below the detection limits, with the exception of barium. The result for barium is less than the estimated method quantification limit (the detection limit multiplied by 3.3). A literature search was carried out, and this was found to be common and is indicative of the high-level GMP (Good Manufacturing Practice) adhered to by the toy industry. The spike recoveries were all within acceptable limits (within 10% of the prepared values). Reanalysis of the same samples on the following day (Analysis B) demonstrates good reproducibility, again with all samples below the detection limits, with the exception of barium, and comparable results for the spike recoveries (shown in Table 5). 

Conclusion

In response to the heightened concern over the presence of toxic trace elements in toy products and the potential risks to children, it is clear that an accurate and reliable means of analytical testing is required. Regulatory standards around the world typically focus on the use of ICP emission spectroscopy as the preferred technique for the analysis of toxic trace elements in toy samples.

ICP emission spectroscopy is a true multielement technique with exceptional sample throughput and a wide analytical range. Typically, ICP emission instrumentation is considered to be complex and requires an operator with a high level of scientific competency. However, the analysis of migratory elements from toys in hydrochloric acid using ICP emission spectroscopy has been simplified via the use of method templates within the instrumentation software.

The use of a preloaded method template with such instrumentation provides a total solution to ensure that the toy samples are regulatory compliant. These tools enable both novice and experienced analysts to achieve reliable results with minimal requirements for method development.

References

  1. www.ecocenter.org/press/releases/20071205.php.
  2. EN71 Safety of Toys—Part 3: Migration of Certain Elements”; European Committee for Standardization (CEN), Ave. Marnix 17, B-1000 Brussels; www.cen.eu.
  3. ASTM Standard F963, 2008, “Standard Consumer Safety Specification for Toy Safety”; ASTM International, West Conshohocken, PA; www.astm.org.

Mr. Cassap is Applications Specialist, Thermo Fisher Scientific, SolAAR House, 19 Mercers Row, Cambridge CB5 8BZ, U.K.; tel.: +44 (0) 1223 347 417; e-mail: matthew.cassap@thermofisher.com.

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