Does your Bamboo Coffee Cup Give off Melamine?

Importance of the Topic

Bamboo coffee-to-go cups and similar kitchenware combine melamine-formaldehyde resin with bamboo fibers to achieve strength and aesthetic appeal. However, under hot-fill conditions, these materials may release melamine into food and beverages. Chronic exposure to melamine has been linked to kidney stone formation and renal damage, making reliable detection and quantification of migration critical for consumer safety and regulatory compliance.

Objectives and Study Overview

This study aimed to develop and validate a hydrophilic interaction liquid chromatography (HILIC) method for quantifying melamine migration from two bamboo coffee-to-go cups and one bamboo children’s cup. The analysis was performed on the Agilent 1260 Infinity II Prime LC System equipped with a high-sensitivity diode array detector to ensure detection below the European specific migration limit (SML) of 2.5 mg/kg.

Methodology and Instrumentation

Sample Preparation and Migration Testing:

• Cups filled with water containing 3% acetic acid at 70 °C and covered to limit evaporation.
• Exposure time: 2 hours, repeated for three migration cycles to simulate repeated use.
• Simulant volume recorded and aliquots diluted tenfold with acetonitrile for HILIC analysis.

Instrumentation and Chromatographic Conditions:

• Agilent 1260 Infinity II Prime LC including Flexible Pump, Vialsampler with thermostat, Multicolumn Thermostat, and Diode Array Detector HS with InfinityLab Max-Light cartridge cell.
• Column: Poroshell 120 HILIC-Z (2.1×100 mm, 2.7 μm).
• Mobile phase: A) 10 mM ammonium formate in water (pH 3); B) acetonitrile/200 mM ammonium formate in water (95/5, v/v); gradient from 100% B to 60% B in 4 min.
• Flow rate: 0.5 mL/min; column temperature: 30 °C; detection at 240 nm.

Main Results and Discussion

Method Performance:

• Calibration linearity between 61.8 and 3,090 ng/mL with R² >0.9999.
• Limit of detection (LOD): ~13 ng/mL; limit of quantification (LOQ): ~42 ng/mL, suitable for detecting migration below the SML after dilution.
• Precision: retention time RSD 0.11%, area RSD 1.42% (n=10 at 289 ng/mL).

Migration Findings:

• All three cups released measurable melamine in each migration cycle.
• In the third use cycle, one coffee-to-go cup and the children’s cup exceeded the regulatory SML of 2.5 mg/kg.
• Repeated use led to increasing melamine migration, consistent with material degradation under hot acidic conditions.

Benefits and Practical Applications of the Method

• High sensitivity and precision ensure confident measurement below regulatory limits.
• Rapid HILIC separation of polar melamine with good peak shape and retention.
• Suitable for routine quality control in laboratories testing food-contact materials.

Future Trends and Potential Applications

• Extension to other polar migrants such as formaldehyde and related degradation products.
• Development of multi-residue HILIC methods for broader screening of food simulants.
• Automation and higher-throughput workflows for regulatory monitoring programs.

Conclusion

The HILIC-based assay on the Agilent 1260 Infinity II Prime LC System offers excellent sensitivity, precision, and linearity for melamine migration analysis. Testing of bamboo-based cups under hot-fill conditions demonstrated that some products exceed the European SML, highlighting the need for stringent quality control and material design optimization. The method supports compliance monitoring and risk mitigation for food-contact articles.

Reference

• Arce MM, et al. Kinetic Models of Migration of Melamine and Formaldehyde from Melamine Kitchenware. J Chromatogr A. 2019;1599:115–124.
• De Lourdes Mendes Finete V, et al. Characterization of Natural Luminescent Properties of Melamine and HPLC-FLD Determination in Plasticware. Talanta. 2014;123:128–134.
• BfR Statement 046/2019. Migration of Melamine and Formaldehyde from Bamboo Kitchenware. 25 Nov 2019.
• Commission Regulation (EU) No 10/2011 on Plastic Materials and Articles for Food Contact. 14 Jan 2011.
• RASFF Portal. Rapid Alert System for Food and Feed. 2020.