Utilizing of magnetic graphene oxide as a nano-sorbent for extraction of melamine from dairy products prior to determination by HPLC

Melamine (2,4,6-triamino-1,3,5-triazine) is illegal material to be used as an additive in food or related ingredients due to its low cost and high nitrogen content (66%). This increasing apparent protein content and provides a wrong amount of protein concentration testing [1]. Melamine can be very toxic at high-dose exposure. The maximum residue level for melamine set by many countries and by WHO are 1 mg kg‒1 in infant formula and 2.5 mg kg‒1 in other milk and milk based products [2]. Therefore, its determination in low amount is important due to human health impact such as kidney stones, renal failure, urinary problems and hyperplasia in the bladder [3]. This study presents synthesis, characherization and application of magnetic graphene oxide for extraction/preconcentration and determination of melamine in dairy products by high performance liquid chromatoghraphy (HPLC) with UV detection. Several factors affecting the extraction procedure such as pH, amount of the adsorbent, contact time, sample volume, type of elution solvent and elution volume were investigated. The optimizing of the parameters was evaluated by employing response surface method (RSM). The cubic model can be explained interaction among effective parameters on the extraction procedure. Under optimal conditions, the limits of detection (LOD) were found to be 0.3 µg mL−1 for melamine in the milk formula sample. The recoveries of melamine from three milk samples (e.g., raw milk, flavored milk and yogurt) were in the range of 97.08–99.98 % with RSDs of 0.5–3.5 %.