Kinetic models of migration of melamine and formaldehyde from melamine kitchenware with data of liquid chromatography

Abstract

European legislation has established a specific migration limit (SML) of 15 mg kg−1 for formaldehyde and 2.5 mg kg−1 for melamine. Formaldehyde resins are used in the manufacture of melamine kitchenware. Formaldehyde is listed in group 1 of the IARC list of carcinogenic compounds. To determine the quantity of formaldehyde and melamine as potential migrants from different types of melamine kitchenware (glass, mug, cutlery, big cup and bowl), a HPLC-DAD method has been implemented. This method is an alternative to the ones proposed in technical guidelines to determine formaldehyde by UV–vis spectrophotometry and melamine by HPLC. The final objective was to fit the migration kinetic curves of these two analytes in melamine kitchenware.

After the method was validated, decision limit (CCα) and detection capability (CCβ) were calculated for both analytes, when the probabilities of false positive (α) and false negative (β) were fixed at 0.05; being CCβ 0.269 mg L−1 and 0.311 mg L−1 for melamine and formaldehyde respectively. CCα and CCβ were also calculated at the SML of both analytes.

The migration testing were conducted with simulant B (3% acetic acid (w/v) in aqueous solution), the conditions of each exposure being 70 °C for 2 h. The quantities of melamine and formaldehyde found in the third exposure of the total kitchenware analysed were between 0.21 and 1.09 mg L−1 and between 0.55 and 3.86 mg L−1, respectively.

Migration kinetic curves were built for each type of kitchenware with the data of sixteen consecutive migration cycles (70 °C each 30 min). The SML for melamine was surpassed in the mug, in the big cup and in the bowl after eleven, thirteen and one cycles, respectively.

When more cycles were carried out in the mug, the values of the accumulated quantity of formaldehyde and melamine were 15.30 and 6.79 mg L−1, respectively, after thirty-two cycles. Both concentrations exceeded the corresponding SML.