The Migration of Elements from Toys and Speciation of Chromium (VI) in Toy Material Using a Low Cost IC-ICP-MS Solution

Importance of the Topic

The analysis of total elemental chromium and its toxic hexavalent form migrating from toy materials is critical for ensuring product safety and regulatory compliance. Hexavalent chromium (Cr VI) is classified as a carcinogen, while trivalent chromium (Cr III) is an essential trace element. Accurate discrimination between these oxidation states at low concentration levels is necessary to assess potential health risks and meet EU toy safety directives.

Goals and Study Overview

This study aimed to develop and validate a low-cost, sensitive method combining ion chromatography (IC) with inductively coupled plasma mass spectrometry (ICP-MS) to quantify total elements and speciated chromium in toy materials. Three sample types—finger paint, pen ink, and titanium dioxide pigment—were subjected to migration testing under the European Standard EN 71-3:2012 protocol, followed by stabilization and analysis of Cr(VI) and total chromium at regulatory threshold levels.

Methodology and Instrumentation

Sample Preparation and Migration

• Toys were leached according to EN 71-3:2012 to simulate consumer exposure.
• Post-migration solutions were stabilized by raising pH above 7.1 using ammonium hydroxide (1 mol/L NH4OH, 1:4 dilution) to prevent Cr(VI) reduction.
• Cr(III) concentrations were calculated by subtracting Cr(VI) from total chromium.

Instrument Configuration

• ICP-MS: Thermo Scientific iCAP Qc with SC-4Q autosampler, operated in He KED mode to minimize polyatomic interferences.
• IC: Thermo Scientific ICS-900 system with AS-DV autosampler and PFA-LC nebulizer; metal-free fluid path.
• Columns: Dionex NG-1 guard column (2 × 50 mm) to remove organics, followed by Dionex AG-7 anion-exchange column (2 × 50 mm) for chromium speciation.
• Eluent: 0.35 mol/L HNO3, isocratic at 0.40 mL/min; injection volume 10 µL.
• Internal standards: Ga (10 ng/g), Rh and Ir (1 ng/g each) added online.

Calibration and Detection Limits

• Cr(VI) standards 0.05–4 ng/mL; 3σ instrumental detection limit 0.9 ng/L.
• Stable Cr(VI) peak separation with retention at ~50 s; void volume peak (~30 s) separated from analyte.

Main Results and Discussion

Total Element Quantification

• Spiked finger paint recoveries ranged from 88 % to 103 % across elements B, Al, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Cd, Sn, Sb, Ba, and Pb.

Chromium Speciation in Migration Solutions

• No measurable Cr(III) or Cr(VI) detected in unspiked leachates.
• Cr(VI) spike recoveries at 0.10 and 0.27 ng/mL ranged from 87 % to 110 %, confirming method accuracy.
• Repeat injections over 24 h demonstrated Cr(VI) stability after pH adjustment.

Benefits and Practical Applications

• Fully metal-free IC-ICP-MS setup avoids organic eluents and carbon-based interferences, simplifying routine operation.
• High sensitivity enables detection of Cr(VI) at single-digit ng/L levels required by current and future regulations.
• Applicable to a broad range of toy materials and other consumer products for QA/QC and regulatory testing.

Future Trends and Opportunities

• Integration of automated sample preparation to increase throughput.
• Extension of speciation protocols to other toxic metals and organometallic species.
• Development of portable or miniaturized hyphenated systems for on-site compliance testing.
• Continued refinement of regulatory limits may drive further enhancements in detection capabilities.

Conclusion

The combined IC-ICP-MS approach using a metal-free fluid path and pH stabilization effectively quantifies total chromium and speciates Cr(VI) in toy migration extracts at low ng/L levels. The method delivers reliable accuracy, precision, and robustness, supporting compliance with EU directives and safeguarding consumer health.

Reference

• European Standard EN 71-3:2012, Safety of Toys—Migration of Certain Elements.
• Thermo Fisher Scientific Application Note AN 43098, Chromium Speciation by IC-ICP-MS.