Artefact formation of formaldehyde in milk powders: Impact of analytical conditions

Formaldehyde (FA) was analyzed in milk powders by isotope dilution LC-MS/MS using 2,4-dinitrophenylhydrazine (DNPH) as the derivatization agent. Analytical conditions (temperature and time) applied for derivatization were shown to strongly impact the levels of FA detected in micronutrient-fortified milk powders. In particular, vitamin C and ferrous iron catalyzed FA formation when derivatization was conducted at 60 °C, as described by several authors. Artefact formation of FA was demonstrated in a model study using 2H2-glycine and a freeze-dried raw cow's milk with added micronutrients. A limited survey of commercial fortified milk powders showed that FA levels were about 4-fold lower when analyses were conducted at room temperature as compared to 60 °C (0.65 ± 0.25 mg/kg and 2.57 ± 0.51 mg/kg, respectively). Based on data obtained at room temperature, FA exposure from fortified milk powders does not represent a safety concern even under worst-case assumptions. This study highlights the need and importance of adopting an international standard for FA analysis in foods.