Assessment of reference materials for toxic elements in milkfish: Implications for food safety in the Philippines

The Metrology in Chemistry Section of the National Metrology Laboratory of the Philippines (NML) developed a candidate reference material (RM) for toxic elements in milkfish to address the food safety issue of consuming milkfish contaminated with toxic elements. The RM was prepared by spiking lyophilized milkfish with known concentrations of lead (Pb) and cadmium (Cd), followed by homogenization and bottling. The homogeneity and stability of Pb and Cd were assessed. The evaluation of the homogeneity of the RM using one-way ANOVA resulted in F calc : 2.08 < F crit : 2.3 in Pb; and F calc : 1.8 < F crit : 2.3 in Cd. It implies that the RM is sufficiently homogeneous. For short-term stability assessment, samples were exposed isochronously in two temperatures (4 °C and 50 °C) for three weeks, and the bottling trend was evaluated through linear regression. Both Pb and Cd passed the criteria, t calc < t crit , confirming the short-term stability of the RMs even under non-ambient conditions. For long-term stability, the RMs were found to be stable for up to six months at −20 °C.